16 SPECIES GIBBON 16 SQUARES QMR (four genera lesser apes four genera great apes)

https://en.wikipedia.org/wiki/Ape

The family Hylobatidae, the lesser apes, include four genera and a total of sixteen species of gibbon, including the lar gibbon and the siamang, all native to Asia. They are highly arboreal and bipedal on the ground. They have lighter bodies and smaller social groups than great apes.

FOUR MAIN BRANCHES

http://www.els.net/WileyCDA/ElsArticle/refId-a0001562.html

The adaptive radiation of platyrrhines unfolded along cladistic lines, with each of the four main lineages occupying a distinct ecological zone characterised by a combination of body size, feeding preference and locomotor habit.

 

The four main branches of the platyrrhine radiation, and some of the living genera, are older than any of the lineages or genera of Old World monkeys or apes.

FOUR ORDERS

https://en.wikipedia.org/wiki/Euarchonta

The Euarchonta are a proposed grandorder of mammals containing four orders: the Scandentia or treeshrews, the Dermoptera or colugos, the extinct Plesiadapiformes, and the Primates.

FOUR CATEGORIES

https://en.wikipedia.org/wiki/Primate

Primates are among the most social of animals, forming pairs or family groups, uni-male harems, and multi-male/multi-female groups.[90] Richard Wrangham stated that social systems of non-human primates are best classified by the amount of movement by females occurring between groups.[91] He proposed four categories:

 

Female transfer systems – females move away from the group in which they were born. Females of a group will not be closely related whereas males will have remained with their natal groups, and this close association may be influential in social behavior. The groups formed are generally quite small. This organization can be seen in chimpanzees, where the males, who are typically related, will cooperate in defense of the group's territory. Among New World Monkeys, spider monkeys and muriquis use this system.[92]

 

A social huddle of ring-tailed lemurs. The two individuals on the right exposing their white ventral surface are sunning themselves.

Male transfer systems – while the females remain in their natal groups, the males will emigrate as adolescents. Polygynous and multi-male societies are classed in this category. Group sizes are usually larger. This system is common among the ring-tailed lemur, capuchin monkeys and cercopithecine monkeys.[58]

Monogamous species – a male–female bond, sometimes accompanied by a juvenile offspring. There is shared responsibility of parental care and territorial defense. The offspring leaves the parents' territory during adolescence. Gibbons essentially use this system, although "monogamy" in this context does not necessarily mean absolute sexual fidelity.[93]

Solitary species – often males who defend territories that include the home ranges of several females. This type of organization is found in the prosimians such as the slow loris. Orangutans do not defend their territory but effectively have this organization.[94]

FOUR CLADES

http://www.nhc.ed.ac.uk/index.php?page=493.166

Since then phylogenetic studies using molecular analysis suggest that eighteen orders of modern eutherians represent four clade or lineages which diverged in the late Cetaceous period after the early eutherians had split from the early marsupials.

 

These findings indicate that members of the order Insectivora should be split among two orders, the order Afrosoricida and the Eulipotyphla, and that four orders of hoofed mammals belong to one clade, the Afrotheria, and three orders � the Perissodatyla, Artiodactyla and Cetacea (whales) - belong to another clade, the Laurasiatheria. As whales now appear to be related to the lineage that gave rise to the hippopotami, a new order has been created to accommodate both cetaceans and artiodactyls - the order Cetartiodactyla. The order Perissodactyla remains as before. The other mammals are split between two other clades - the Xenarthra and Euarchontoglires as listed below. The clades Xenarthra and Afrotheria appear to have evolved in the Southern Hemisphere in South America and Africa respectively; the clades Euarchontoglires and the Laurasiatheria in the Northern Hemisphere. The web pages entitled 'the Tree of Life' explain how molecular analyses led to the order Insectivora being split.

FOUR MAJOR GROUPS OF PLACENTAL MAMMALS- ALL OF THIS IN MY OVER 60 QMR BOOKS I REMEMBER LOOKING THIS UP IN COLLEGE

https://simple.wikipedia.org/wiki/Afrotheria

Biologists made this group based on RNA sequence analysis.[1] Afrotheria are one of four major groups in the Eutheria (placental mammals). Afrotheria means "African animals", "afro" for Africa and "theria" for animals.

TETRA IS FOUR- FOUR SUBSPECIES

https://en.wikipedia.org/wiki/Southern_tamandua

The four recognised subspecies of Tamandua tetradactyla are:

 

T. t. tetradactyla (Linnaeus, 1758) - southern and eastern Brazil, Uruguay

T. t. nigra (Geoffroy, 1803) - northern Brazil, Colombia, Venezuela, Trinidad, the Guianas

T. t. quichua (Thomas, 1927) - Peru, Ecuador, extreme western Brazil

T. t. straminea (Cope, 1889) - southern Brazil, Paraguay, Bolivia, Argentina

FOUR LIVING SPECIES OF ANTEATER

https://en.wikipedia.org/wiki/Giant_anteater

The giant anteater (Myrmecophaga tridactyla), also known as the ant bear, is a large insectivorous mammal native to Central and South America. It is one of four living species of anteaters and is classified with sloths in the order Pilosa. This species is mostly terrestrial, in contrast to other living anteaters and sloths, which are arboreal or semiarboreal. The giant anteater is the largest of its family, 182–217 cm (5.97–7.12 ft) in length, with weights of 33–41 kg (73–90 lb) for males and 27–39 kg (60–86 lb) for females. It is recognizable by its elongated snout, bushy tail, long fore claws, and distinctively colored pelage.

https://www.thoughtco.com/islands-in-greater-and-lesser-antilles-4069042

WHAT ARE THE GREATER ANTILLES?

The Greater Antilles are the four largest islands in the northwestern portion of the Caribbean Sea. This includes Cuba, Hispaniola (the nations of Haiti and the Dominican Republic), Jamaica and Puerto Rico.

FOUR SUPERORDERS

https://en.wikiversity.org/wiki/Mammals

Most placental mammals belong to one of four main superorders: Afrotheria, Euarchontoglires, Laurasiatheria, and Xenarthra.

class Monocotyledonae

https://www.vocabulary.com/dictionary/class%20Monocotyledonae

1

n comprising seed plants that produce an embryo with a single cotyledon and parallel-veined leaves: includes grasses and lilies and palms and orchids; divided into four subclasses or superorders: Alismatidae; Arecidae; Commelinidae; and Liliidae

http://instruction2.mtsac.edu/mcooper/Biology%202/Labs/Protistalab1.pdf

The Stramenopiles include four different clades: 1) the Diatoms, 2) the Golden Algae, 3) the Brown Algae and 4) the Oomycetes (Water Molds).

EUKARYA FOUR SUPERGROUPS

http://www.elcamino.edu/faculty/rsidhu/Biol101/Protists.pdf

Eukarya is now divided into 4 supergroups, Excavata, SAR Clade, Archaeplastida and Unikonta. It replaces the earlier 5-kingdom classification of Monera – all prokaryotes, Protista – early eukaryotes and 3 multicellular kingdoms Plants, Fungi and Animals. Kingdom monera is replaced by 2 new domains Bacteria and Archaea. The classification of domain Eukarya is going on. Molecular data has broken the boundaries between protista and 3 multicellular kingdoms. Eukarya is likely to get more than 20 kingdoms but none of them is protista.

THE FOURTH IS DIFFERENT

https://www.scientificamerican.com/article/genomes-of-giant-viruses-hint-at-fourth-domain-of-life/

Genomes of Giant Viruses Hint at "4th Domain" of Life

Just 7 percent of the viruses' genes match those in existing databases, a finding that confirms that viral diversity is still largely underexplored

https://en.wikipedia.org/wiki/Thomas_Cavalier-Smith

The kingdom Animalia was divided into four subkingdoms: Radiata (phyla Porifera, Cnidaria, Placozoa, and Ctenophora)Myxozoa, Mesozoa, and Bilateria (all other animal phyla).

https://en.wikipedia.org/wiki/Cavalier-Smith%27s_system_of_classification

By mid-nineteenth century, microscopic organisms were generally classified into four groups:

 

Protozoa (primitive animals),

Protophyta (primitive plants),

Phytozoa (animal-like plants & plant-like animals), and

Bacteria (formerly regarded as plants).[7]

http://eol.org/info/456

The protozoa are divided into four major groups: the ciliates, the flagellates, the heliozoans, and the amoebas.

http://www.microbeworld.org/types-of-microbes/protista/protozoa

The four main subgroups of protozoa are the ciliates, the flagellates, the sarcodina, and the apicomplexans.

WHITTAKER FOUR KINGDOMS OF LIFE

https://en.wikipedia.org/wiki/Cavalier-Smith%27s_system_of_classification

 

Fungi are more closely related to animals than to plants. By 1959, Robert Harding Whittaker (1920–1980) proposed that fungi, which were formerly classified as plants, be given their own kingdom. His four kingdoms of life were:

 

the Protista, (or unicellular organisms);

the Plantae, (or multicellular plants);

the Fungi; and

the Animalia (or multicellular animals).

https://en.wikipedia.org/wiki/Cavalier-Smith%27s_system_of_classification

In his 1998 scheme, the animal kingdom was divided into four subkingdoms:

 

Radiata (phyla Porifera, Cnidaria, Placozoa, and Ctenophora),

Myxozoa,

Mesozoa, and

Bilateria (all other animal phyla).

http://www.davidmoore.org.uk/Assets/Mostly_Mycology/Jon_Dixon/kingdom_fungi.htm

The last two phyla are combined in the Subkingdom Dikarya (Hibbett et al. 2007) and there are four subphyla that were traditionally placed in the phylum Zygomycota (1,065 species in 168 genera), though this traditional phylum is polyphyletic and is currently in an uncertain state (see below).

 

For the moment remember that when fungi were still classified in the Plant Kingdom (Subkingdom Cryptogamia, Division Fungi, Subdivision Eumycotina) they were separated into four classes:

 

Phycomycetes;

Ascomycetes;

Basidiomycetes;

Deuteromycetes (also known as Fungi Imperfecti because they lacked a sexual cycle).

Major Groups of Arthropods

Arthropods are divided into four subphyla. These are the Chelicerata, the Crustacea, the Uniramia, and the Trilobita. The last consists exclusively of extinct forms.

http://www.encyclopedia.com/plants-and-animals/animals/zoology-invertebrates/arthropoda

Subphylum Chelicerata.

FOUR CLASSES OF MOLLUSCS

https://quizlet.com/3308364/adaptation-and-variation-in-four-classes-of-molluscs-flash-cards/

4 classes in Phylum Mollusca

Class Polyplacophora - Chitons

Class Vivavlvia - Clams

Class Gastropoda - Snails

Class Cephaloda - Squid

I'm a paragraph. Click here to add your own text and edit me. It's easy.

I'm a paragraph. Click here to add your own text and edit me. It's easy.

LOOP OF HENLE FOUR PARTS

https://en.wikipedia.org/wiki/Loop_of_Henle

The loop of Henle can be divided into four parts:

 

Thin descending limb of loop of Henle

The thin descending limb has low permeability to ions and urea, while being highly permeable to water. The loop has a sharp bend in the renal medulla going from descending to ascending thin limb.

Thin ascending limb of loop of Henle

The thin ascending limb is impermeable to water, but it is permeable to ions.

Ascending limb of loop of Henle

Sodium (Na+), potassium (K+) and chloride (Cl−) ions are reabsorbed from the urine by secondary active transport by a Na-K-Cl cotransporter (NKCC2). The electrical and concentration gradient drives more reabsorption of Na+, as well as other cations such as magnesium (Mg2+) and calcium (Ca2+).

Cortical thick ascending limb

The cortical thick ascending limb drains urine into the distal convoluted tubule.[3]

The tissue type of the loop is simple squamous epithelium. The "thick" and "thin" terminology does not refer to the size of the lumen, but to the size of the epithelial cells.[4] The loop is also sometimes called the Nephron loop.

LOOP OF HENLE FOUR PARTS

https://en.wikipedia.org/wiki/Loop_of_Henle

The loop of Henle can be divided into four parts:

 

Thin descending limb of loop of Henle

The thin descending limb has low permeability to ions and urea, while being highly permeable to water. The loop has a sharp bend in the renal medulla going from descending to ascending thin limb.

Thin ascending limb of loop of Henle

The thin ascending limb is impermeable to water, but it is permeable to ions.

Ascending limb of loop of Henle

Sodium (Na+), potassium (K+) and chloride (Cl−) ions are reabsorbed from the urine by secondary active transport by a Na-K-Cl cotransporter (NKCC2). The electrical and concentration gradient drives more reabsorption of Na+, as well as other cations such as magnesium (Mg2+) and calcium (Ca2+).

Cortical thick ascending limb

The cortical thick ascending limb drains urine into the distal convoluted tubule.[3]

The tissue type of the loop is simple squamous epithelium. The "thick" and "thin" terminology does not refer to the size of the lumen, but to the size of the epithelial cells.[4] The loop is also sometimes called the Nephron loop.

FOUR PARTS
https://radiopaedia.org/articles/occipital-bone
The occipital bone is composed of four parts:

squamous part: external/internal surfaces
basilar part (basiocciput): lower/upper surfaces
lateral (jugular) parts (two): under/upper surfaces

FOUR PARTS FUSION

https://radiopaedia.org/articles/occipital-bone

Development

 

The apical portion of the squamous part (above highest nuchal line): ossifies in membrane. Otherwise, the four parts ossify in cartilage.

 

Four parts are present at birth. Fusion occurs:

 

2nd year: squamous and jugulars

6th year: jugulars with basilar

25th year: basilar with basisphenoid

CRUCIATE EMINENCE THE CROSS

http://www.theodora.com/anatomy/the_occipital_bone.html

The internal surface is deeply concave and divided into four fossæ by a cruciate eminence. The upper two fossæ are triangular and lodge the occipital lobes of the cerebrum; the lower two are quadrilateral and accommodate the hemispheres of the cerebellum. At the point of intersection of the four divisions of the cruciate eminence is the internal occipital protuberance.

https://www.kenhub.com/en/library/anatomy/the-maxilla

The maxilla consists of the body and its four projections: the frontal, zygomatic, palatine and alveolar processes.

TEMPORAL BONE FOUR PARTS

https://www.kenhub.com/en/library/anatomy/the-temporal-bone

The temporal bone is a large, bilaterally symmetrical bone which forms the base of the cranial vault (along with the occipital bone) and ascends to participate in the lateral walls of the skull. It is divided into four parts: the squamous part, the tympanic part, the styloid process and the petrous part.

FOUR PROCESSES FOUR BORDERS

 

https://en.wikipedia.org/wiki/Zygomatic_bone

In the human skull, the zygomatic bone (cheekbone or malar bone) is a paired bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. It is situated at the upper and lateral part of the face and forms the prominence of the cheek, part of the lateral wall and floor of the orbit, and parts of the temporal and infratemporal fossa. It presents a malar and a temporal surface; four processes, the frontosphenoidal, orbital,

maxillary, and temporal; and four borders.

 

The zygomatic articulates with four bones: the frontal, sphenoid, temporal, and maxilla.

AS I SAID THERE IS SO MUCH THAT I LEARNED AT UCSD AND OTHER PLACES THAT I CANT REMEMBER OR DONT KNOW HOW TO EXPLAIN FOR INSTANCE FROM RENOWNED NOVELS THAT WERE THE QUADRANT PATTERN THAT I FORGET THEIR NAMES AND SO ON

http://vanat.cvm.umn.edu/NeuroLectPDFs/LectNociceptionI.pdf

IT GOES UP TO FOURTH ORDER NEURONS AND FOURTH ORDER IS TRANSCENDENT AT UCSD MAINLY TEACH UP TO THIRD ORDER

 

C. 2nd Order neurons: Marginal Nucleus or Nucleus Proprius D. Axons of these 2nd order neurons ascend ipsilaterally to the

upper cervical spinal cord to synapse on 3rd order neurons

located in the Lateral Cervical Nucleus (see fig 1 below) E. Axons from 3rd order neurons in the lateral cervical nucleus

cross the midline and ascend to the contralateral thalamus

where they terminate on 4th order neurons.

F. The axons of these 4th order neurons project to the

somatosensory area of the cerebral cortex.

FOUR BUNDLES OF FIBRES

https://www.kenhub.com/en/library/anatomy/commissural-pathways

The commissure of the fornix is one of the four bundles of fibres contained in the fornix of the brain. The remaining three being the postcommissural fornix lying behind the anterior commissure, the precommissural fornix, which descends anteriorly to the anterior commissure, and a bundle of fibres running above the splenium of the corpus callosum. This bundle of running fibres is referred to as the dorsal fornix

DOPAMINERGIC CELL GROUPS GO UP TO GROUP 16 16 SQUARES QMR

https://en.wikipedia.org/wiki/Dopaminergic_cell_groups

Cell group A15[edit]

Group A15 exists in a few species, such as sheep, and immunoreactive for tyrosine hydroxylase, a precursor of dopamine, in many other species including rodents and primates. It is located in ventral and dorsal components within the preoptic periventricular nucleus and adjacent parts of the anterior hypothalamic region. It is continuous caudally with the dopaminergic group A14.[7]

 

Cell group A16[edit]

Group A16 is located in the olfactory bulb of vertebrates, including rodents and primates.[2]

BASAL GANGLIA FOUR STRUCTURES

https://en.wikipedia.org/wiki/Basal_ganglia

In terms of anatomy, the basal ganglia are divided into four distinct structures, depending on how superior or rostral they are (in other words depending on how close to the top of the head they are): Two of them, the striatum and the pallidum, are relatively large; the other two, the substantia nigra and the subthalamic nucleus, are smaller. In the illustration to the right, two coronal sections of the human brain show the location of the basal ganglia components. Of note, and not seen in this section, the subthalamic nucleus and substantia nigra lie farther back (posteriorly) in the brain than the striatum and pallidum.

CRUCIATUS MEANS CROSS

https://species.wikimedia.org/wiki/Selatosomus_cruciatus

Selatosomus cruciatus

 

Selatosomus cruciatus

Taxonavigation

TETRAMEROUS SYMMETRY

http://www.biologydiscussion.com/animals-2/5-main-types-of-symmetry-seen-in-animals/32414

(i) Tetramerous symmetry:

 

ADVERTISEMENTS:

 

 

Many jelly fishes possess 4 radial canals and the body can be divided into 4 equal parts. Hence the ani­mals exhibit tetramerous raidal symmetry (Fig. 9.3B).

FOUR GROUPS ARTHROPODS

https://www.slideshare.net/felipecuervo/types-of-invertebrates

ARTHROPODS GROUPSAre divide into four groups Insects ,Arachnid,crustaceans and myriapods

TYPICAL ANTHER FOUR MICROSPORANGIA

https://en.wikipedia.org/wiki/Stamen

A typical anther contains four microsporangia. The microsporangia form sacs or pockets (locules) in the anther (anther sacs or pollen sacs). The two separate locules on each side of an anther may fuse into a single locule. Each microsporangium is lined with a nutritive tissue layer called the tapetum and initially contains diploid pollen mother cells. These undergo meiosis to form haploid spores. The spores may remain attached to each other in a tetrad or separate after meiosis. Each microspore then divides mitotically to form an immature microgametophyte called a pollen grain.

FOUR STAMENS

https://en.wikipedia.org/wiki/Plant_reproductive_morphology

Members of the birch family (Betulaceae) are examples of monoecious plants with unisexual flowers. A mature alder tree (Alnus species) produces long catkins containing only male flowers, each with four stamens and a minute perianth, and separate stalked groups of female flowers, each without a perianth.[8] (See the illustration of Alnus serrulata.)

 

Most hollies (members of the genus Ilex) are dioecious. Each plant produces either functionally male flowers or functionally female flowers. In Ilex aquifolium (see the illustration), the common European holly, both kinds of flower have four sepals and four white petals; male flowers have four stamens, female flowers usually have four non-functional reduced stamens and a four-celled ovary.[9] Since only female plants are able to set fruit and produce berries, this has consequences for gardeners. Amborella represents the first known group of flowering plants to separate from their common ancestor. It too is dioecious; at any one time, each plant produces either flowers with functional stamens but no carpels, or flowers with a few non-functional stamens and a number of fully functional carpels. However, Amborella plants may change their "gender" over time. In one study, five cuttings from a male plant produced only male flowers when they first flowered, but at their second flowering three switched to producing female flowers.[10]

FOUR LOBED

https://en.wikipedia.org/wiki/Ilex_aquifolium

The flowers are white, four-lobed, and pollinated by bees. Holly is dioecious, meaning that there are male plants and female plants. The sex cannot be determined until the plants begin flowering, usually between 4 and 12 years of age. In male specimens, the flowers are yellowish and appear in axillary groups. In the female, flowers are isolated or in groups of three and are small and white or slightly pink, and consist of four petals and four sepals partially fused at the base.

FOURTH DIFFERENT

https://en.wikipedia.org/wiki/File:Euphorbiinae_tree.png

https://en.wikipedia.org/wiki/Euphorbia

Euphorbia can be divided into four subgenera, each containing several not yet sufficiently studied sections and groups. Of these, Esula is the most basal. Chamaesyce and Euphorbia are probably sister taxa, but very closely related to Rhizanthium. Extensive xeromorph adaptations in all probability evolved several times; it is not known if the common ancestor of the cactus-like Rhizanthium and Euphorbia lineages was xeromorphic—in which case a more normal morphology would have re-evolved namely in Chamaesyce—or whether extensive xeromorphism is entirely polyphyletic even to the level of the subgenera.

FOUR BASIC PARTS OF FLOWER

https://simple.wikipedia.org/wiki/Flower

Four basic parts[change | change source]

Flowers have four basic parts, from the outside in they are:

 

The perianth, the vegetative parts

The calyx: the outermost whorl consisting of units called sepals. These are often green and enclose the rest of the flower in the bud. They may be absent, or they may be petal-like in some species.

The corolla: the petals, usually thin, soft and often colored to attract animals that help pollination.

The reproductive parts

The androecium, the male part, is the stamens

The gynoecium, the female parts,

FOUR GROUPS OF HIV-1

http://perspectivesinmedicine.cshlp.org/content/1/1/a006841.full

HIV-1 origins. The phylogenetic relationships of representative SIVcpz, HIV-1, and SIVgor strains are shown for a region of the viral pol gene (HIV-1/HXB2 coordinates 3887–4778). SIVcpz and SIVgor sequences are shown in black and green, respectively. The four groups of HIV-1, each of which represents an independent cross-species transmission, are shown in different colors. Black circles indicate the four branches where cross-species transmission-to-humans has occurred. White circles indicate two possible alternative branches on which chimpanzee-to-gorilla transmission occurred. Brackets at the right denote SIVcpz from P. t. troglodytes (SIVcpzPtt) and P. t. schweinfurthii (SIVcpzPts), respectively. The phylogenetic tree was estimated using maximum likelihood methods (Guindon and Gascuel 2003). The scale bar represents 0.05 nucleotide substitutions per site.

THE FOUR GROUPS OF HIV THE FOURTH IS DIFFERENT

http://www.webmd.com/hiv-aids/types-strains-hiv#1

HIV-1 has four groups -- one large one and three much smaller ones.

 

Group M (Major)

 

This group is responsible for the HIV epidemic. Nearly 90% of all HIV-1 cases stem from this group.

 

 

The group has nine named strains: A, B, C, D, F, G, H, J, and K. Some of these have sub-strains. Researchers find new strains all the time as they learn more about HIV-1 group M.

 

The B strain is the most common in the U.S. Worldwide, the most common HIV strain is C.

 

Scientists haven't done much research on strains other than B, so information on the rest is limited. The drugs that treat the B strain (antiretroviral drugs) also work on most others.

 

Groups N, O, and P

 

The smaller HIV-1 groups are rare outside of west central Africa, specifically Cameroon. They are:

 

N (New, Not-M, or Not O group): This form of the virus has only been seen in a small group of people in Cameroon. Researchers haven't named any strains for this group because there are so few cases of it.

O (Outlier group): This group has almost as many variations as the M group. However, researchers haven't identified its separate strains yet because it's so rare.

P group: This is the newest group of HIV-1. It was given its own name because of how different it is from the M, N, and O strains.

FOUR STRAINS OF HIV

http://www.telegraph.co.uk/news/science/science-news/11446094/Half-of-human-Aids-came-from-gorillas.html

HIV (HIV-1) has at least four strains. Known as Groups M, N, O and P, each one had its own origin - from ape to man, on at least four separate occasions.

FOUR MAJOR SEROTYPES

https://en.wikipedia.org/wiki/Hepatitis_B

The virus is divided into four major serotypes (adr, adw, ayr, ayw) based on antigenic epitopes presented on its envelope proteins, and into eight major genotypes (A–H). The genotypes have a distinct geographical distribution and are used in tracing the evolution and transmission of the virus. Differences between genotypes affect the disease severity, course and likelihood of complications, and response to treatment and possibly vaccination.[46][47] There are two other genotypes I and J but they are not universally accepted as of 2015[48]

 

There are four known genes encoded by the genome, called C, X, P, and S. The core protein is coded for by gene C (HBcAg), and its start codon is preceded by an upstream in-frame AUG start codon from which the pre-core protein is produced. HBeAg is produced by proteolytic processing of the pre-core protein. In some rare strains of the virus known as Hepatitis B virus precore mutants, no HBeAg is present.[40] The DNA polymerase is encoded by gene P. Gene S is the gene that codes for the surface antigen (HBsAg). The HBsAg gene is one long open reading frame but contains three in frame "start" (ATG) codons that divide the gene into three sections, pre-S1, pre-S2, and S. Because of the multiple start codons, polypeptides of three different sizes called large (the order from surface to the inside: pre-S1, pre-S2, and S ), middle (pre-S2, S), and small (S) [41] are produced.[42] The function of the protein coded for by gene X is not fully understood but it is associated with the development of liver cancer. It stimulates genes that promote cell growth and inactivates growth regulating molecules.[43]

 

Pathogenesis[edit]

 

Hepatitis B virus replication

The life cycle of hepatitis B virus is complex. Hepatitis B is one of a few known pararetroviruses: non-retroviruses that still use reverse transcription in their replication process. The virus gains entry into the cell by binding to NTCP [44] on the surface and being endocytosed. Because the virus multiplies via RNA made by a host enzyme, the viral genomic DNA has to be transferred to the cell nucleus by host proteins called chaperones. The partially double-stranded viral DNA is then made fully double stranded by a viral polymerase and transformed into covalently closed circular DNA (cccDNA). This cccDNA serves as a template for transcription of four viral mRNAs by host RNA polymerase. The largest mRNA, (which is longer than the viral genome), is used to make the new copies of the genome and to make the capsid core protein and the viral DNA polymerase. These four viral transcripts undergo additional processing and go on to form progeny virions that are released from the cell or returned to the nucleus and re-cycled to produce even more copies.[42][45]

FOUR PHASES

https://www.hepmag.com/basics/hepatitis-b-basics/hepatitis-b-progression

Chronic hepatitis B infection is characterized by four phases. Not everyone will experience all four phases, and the lengths of the phases vary among people. Your medical provider will order lab tests regularly to monitor changes in your condition. The phase you are in is determined by multiple lab tests, not by a single result. To learn more about these tests, visit Hepatitis B Lab Tests.

FOUR GENOTYPES

https://en.wikipedia.org/wiki/Hepatitis_E

Classification[edit]

There is only one serotype of the virus and classification is based on the nucleotide sequences of the genome.[12] Genotype 1 has been classified into five subtypes, genotype 2 into two subtypes and genotypes 3 and 4 have been into ten and seven subtypes respectively.Differences have been noted between the different genotypes. For genotype 1, the age at which incidence peaks is between 15 and 35 years and mortality is about 1%. Genotype 3 and 4—the most common in Japan—are more common in people older than 60 years and the mortality is between 5 and 10%.[medical citation needed]

 

Distribution[edit]

Genotype 1 has been isolated from tropical and several subtropical countries in Asia and Africa.[13]

Genotype 2 has been isolated from Mexico, Nigeria, and Chad.[14]

Genotype 3 has been isolated almost worldwide including Asia, Europe, Oceania, North and South America.[15]

Genotype 4 appears to be limited.[13]

FOUR PHASES

http://emedicine.medscape.com/article/775507-clinical

The clinical presentation of infectious hepatitis varies with the individual, as well as with the specific causative virus. Some patients may be entirely asymptomatic or only mildly symptomatic at presentation. Others may present with rapid onset of fulminant hepatic failure (FHF). The classic presentation of infectious hepatitis involves four phases, as follows:

Phase 1 (viral replication phase) – Patients are asymptomatic; laboratory studies demonstrate serologic and enzyme markers of hepatitis

Phase 2 (prodromal phase) – Patients experience anorexia, nausea, vomiting, alterations in taste, arthralgias, malaise, fatigue, urticaria, and pruritus, and some develop an aversion to cigarette smoke; when seen by a healthcare provider during this phase, patients are often diagnosed as having gastroenteritis or a viral syndrome

Phase 3 (icteric phase) – Patients may note dark urine, followed by pale-colored stools; in addition to the predominant gastrointestinal (GI) symptoms and malaise, patients become icteric and may develop right upper quadrant pain with hepatomegaly

Phase 4 (convalescent phase) – Symptoms and icterus resolve, liver enzymes return to normal

https://en.wikipedia.org/wiki/Glyoxylate_cycle

The four carbon succinate molecule can be transformed into a variety of carbohydrates through combinations of other metabolic processes; the plant can synthesize molecules using acetate as a source for carbon. The Acetyl CoA can also react with glyoxylate to produce some NADPH from NADP+, which is used to drive energy synthesis in the form of ATP later in the Electron Transport Chain. [4]

TETRAMERS

https://en.wikipedia.org/wiki/Reactive_oxygen_species

Superoxide dismutases (SOD) are a class of enzymes that catalyze the dismutation of superoxide into oxygen and hydrogen peroxide. As such, they are an important antioxidant defense in nearly all cells exposed to oxygen. In mammals and most chordates, three forms of superoxide dismutase are present. SOD1 is located primarily in the cytoplasm, SOD2 in the mitochondria and SOD3 is extracellular. The first is a dimer (consists of two units), while the others are tetramers (four subunits). SOD1 and SOD3 contain copper and zinc ions, while SOD2 has a manganese ion in its reactive centre. The genes are located on chromosomes 21, 6, and 4, respectively (21q22.1, 6q25.3 and 4p15.3-p15.1).

TETRAMERS

https://en.wikipedia.org/wiki/Superoxide_dismutase

Iron – Many bacteria contain a form of the enzyme with iron (Fe-SOD); some bacteria contain Fe-SOD, others Mn-SOD, and some (such as E. coli) contain both. Fe-SOD can also be found in the chloroplasts of plants. The 3D structures of the homologous Mn and Fe superoxide dismutases have the same arrangement of alpha-helices, and their active sites contain the same type and arrangement of amino acid side-chains. They are usually dimers, but occasionally tetramers.

 

Three forms of superoxide dismutase are present in humans, in all other mammals, and most chordates. SOD1 is located in the cytoplasm, SOD2 in the mitochondria, and SOD3 is extracellular. The first is a dimer (consists of two units), whereas the others are tetramers (four subunits). SOD1 and SOD3 contain copper and zinc, whereas SOD2, the mitochondrial enzyme, has manganese in its reactive centre. The genes are located on chromosomes 21, 6, and 4, respectively (21q22.1, 6q25.3 and 4p15.3-p15.1).

 

There are three well-known and -studied classes of SOD metallic coenzymes that exist in plants. First, Fe SODs consist of two species, one homodimer (containing 1-2 g Fe) and one tetramer (containing 2-4 g Fe).

 

PDB: 1VAR​; Borgstahl GE, Parge HE, Hickey MJ, Johnson MJ, Boissinot M, Hallewell RA, Lepock JR, Cabelli DE, Tainer JA (April 1996). "Human mitochondrial manganese superoxide dismutase polymorphic variant Ile58Thr reduces activity by destabilizing the tetrameric interface". Biochemistry. 35 (14): 4287–97. PMID 8605177. doi:10.1021/bi951892w.

Jump up ^

IT IS A TETRAMER

https://en.wikipedia.org/wiki/Catalase

Catalase is a tetramer of four polypeptide chains, each over 500 amino acids long.[5] It contains four porphyrin heme (iron) groups that allow the enzyme to react with the hydrogen peroxide. The optimum pH for human catalase is approximately 7,[6] and has a fairly broad maximum (the rate of reaction does not change appreciably at pHs between 6.8 and 7.5).[7] The pH optimum for other catalases varies between 4 and 11 depending on the species.[8] The optimum temperature also varies by species.[9]

 

Human catalase forms a tetramer composed of four subunits, each of which can be conceptually divided into four domains.[10] The extensive hydrophobic core of each subunit is generated by an eight-stranded antiparallel b-barrel (b1-8), with nearest neighbor connectivity capped by b-barrel loops on one side and a9 on the other.[10] A helical domain at one face of the b-barrel is composed of four C-terminal helices (a16, a17, a18, and a19) and four helices derived from residues between b4 and b5 (a4, a5, a6, and a7).[10]

TETRAMERIC- FOUR A HELIX

https://en.wikipedia.org/wiki/Hemerythrin

Hemerythrin typically exists as a homooctamer or heterooctamer composed of α- and β-type subunits of 13-14 kDa each, although some species have dimeric, trimeric and tetrameric hemerythrins. Each subunit has a four-α-helix fold binding a binuclear iron centre. Because of its size hemerythrin is usually found in cells or "corpuscles" in the blood rather than free floating.

FOURTH SUBRACE OF EUROPEANS- FOURTH DIFFERENT

https://en.wikipedia.org/wiki/Caucasian_race

In 1920, H. G. Wells referred to the Mediterranean race as the Iberian race. He regarded it as a fourth sub-race of the Caucasoid race, along with the Aryan, Semitic, and Hamitic sub-races. He stated that the main ethnic group that most purely represented the racial stock of the Iberian race was the Basques, and that the Basques were the descendants of the Cro-Magnons.[45]

FOUR RACES

https://en.wikipedia.org/wiki/Mediterranean_race

In the 19th century, the division of humanity into distinct races became a matter for scientific debate. In 1870, Thomas Huxley argued that there were four basic racial categories (Xanthochroic, Mongoloid, Australioid and Negroid). The Xanthochroic race were the "fair whites" of north and central Europe. According to Huxley,

 

On the south and west this type comes into contact and mixes with the "Melanochroi," or "dark whites"...In these regions are found, more or less mixed with Xanthochroi and Mongoloids, and extending to a greater or less distance into the conterminous Xanthochroic, Mongoloid, Negroid and Australioid areas, the men whom I have termed Melanochroi, or dark whites. Under its best form this type is exhibited by many Irishmen, Welshmen and Bretons, by Spaniards, South Italians, Greeks, Armenians, Arabs and high-caste Brahmins...I am much disposed to think that the Melanochroi are the result of an intermixture between the Xanthochroi and the Australoids. It is to the Xanthochroi and Melanochroi, taken together, that the absurd denomination of "Caucasian" is usually applied.[12]

THE FOUR GREAT BRANCHES OF THE MEDITERRANEAN STOCK

https://en.wikipedia.org/wiki/Mediterranean_race

The four great branches of the Mediterranean stock were the Libyans, the Ligurians, the Pelasgians and the Iberians

TRANSCENDENT FOURTH RACE EUROPE

https://en.wikipedia.org/wiki/The_Races_of_Europe_(Ripley)

The conflict between Ripley and Deniker was criticized by Jan Czekanowski, who states that "the great discrepancies between their claims decrease the authority of anthropology", and what is more, he points out that both Deniker and Ripley had one common feature, as they both omitted the existence of an Armenoid race, which Czekanowski claimed to be one of the four main races of Europe, met especially among the Eastern and Southern Europeans.[3] Ripley was the first American recipient of the Huxley Medal of the Royal Anthropological Institute in 1908 on account of his contributions to anthropology.

http://stdgen.northwestern.edu/stdgen/bacteria/hhv2/herpes.html

Virion Structure

All herpesvirus virions have four structural elements.

Core. The core consists of a single linear molecule of dsDNA in the form of a torus.

Capsid. Surrounding the core is an icosahedral capsid with a 100 nm diameter constructed of 162 capsomeres.

Tegument. Between the capsid and envelope is an amorphous, sometimes asymmetrical, feature named the tegument. It consists of viral enzymes, some of which are needed to take control of the cell's chemical processes and subvert them to virion production, some of which defend against the host cell's immediate responses, and others for which the function is not yet understood.

Envelope. The envelope is the outer layer of the virion and is composed of altered host membrane and a dozen unique viral glycoproteins. They appear in electron micrographs as short spikes embedded in the envelope.

https://www.ncbi.nlm.nih.gov/books/NBK8157/

Herpesviruses have a unique four-layered structure: a core containing the large, double-stranded DNA genome is enclosed by an icosapentahedral capsid which is composed of capsomers. The capsid is surrounded by an amorphous protein coat called the tegument. It is encased in a glycoprotein-bearing lipid bilayer envelope.

THE FOURTH HEAD OF THE TRICEPS

https://en.wikipedia.org/wiki/Triceps_brachii_muscle

Many mammals, such as dogs, cattle, and pigs, have a fourth head, the accessory head. It lies between the lateral and medial heads.[2] In humans, the anconeus is sometimes loosely called "the fourth head of the triceps brachii".

SPLITS INTO FOUR TENDONS

http://teachmeanatomy.info/upper-limb/muscles/anterior-forearm/

The flexor digitorum superficialis is the only muscle of the intermediate compartment. It can sometimes be classed as a superficial muscle, but in most cadavers it lies between the deep and superficial muscle layers.

 

The muscle is a good anatomical landmark in the forearm – the median nerve and ulnar artery pass between its two heads, and then travel posteriorly.

 

Attachments: It has two heads – one originates from the medial epicondyle of the humerus, the other from the radius. The muscle splits into four tendons at the wrist, which travel through the carpal tunnel, and attaches to the middle phalanges of the four fingers.

FANS OUT INTO FOUR TENDONS

https://en.wikipedia.org/wiki/Flexor_digitorum_profundus_muscle

Flexor digitorum profundus originates in the upper 3/4 of the anterior and medial surfaces of the ulna, interosseous membrane and deep fascia of the forearm. The muscle fans out into four tendons (one to each of the second to fifth fingers) to the palmar base of the distal phalanx.

QUAD MEANS FOUR

https://en.wikipedia.org/wiki/Pronator_quadratus_muscle

Pronator quadratus is a square shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the hand.

FOUR MUSCLES

http://anatomyzone.com/tutorials/musculoskeletal/muscles-of-the-forearm/

Superficial Layer

In the superficial layer you've got four muscles, you've got the flexor carpi ulnaris, the palmaris longus, the flexor carpi radialis, and the pronator teres.

FOUR TENDONS FLEXOR DIGITORUM

http://anatomyzone.com/tutorials/musculoskeletal/muscles-of-the-forearm/

It originates on the medial epicondyle of the humerus also on the ulna and it also originates on this radial, this oblique line on the radius. It then runs down and you've got these four tendons which pass through the carpal tunnel, so the carpel tunnel is this space between the flexor retinaculum and the carpal bones, and the median nerve passes through this, and when it, when the contents of the carpal tunnel get compressed, you get muscle weakness and loss of sensation, and I'll talk a bit about that in another tutorial.

 

 

You’ve got these four tendons of the flexor digitorum superficialis which run through the...underneath the flexor retinaculum, and they insert onto the middle phalanx of the index, middle, ring and little fingers. This tendon is quite interesting because it actually split and inserts onto the lateral margins of the middle phalanx, and it allows this other tendon to pass through, so the tendon of the flexor digitorum profundus, to pass through.

EXTENSOR DIGITORUM FOUR TENDONS

http://anatomyzone.com/tutorials/musculoskeletal/muscles-of-the-forearm/

Medial to this muscle, we’ve got the extensor digitorum, which originates on the lateral epicondyle just medial to the extensor carpi radialis brevis. You can see this muscle here. This is the outline of the muscle. And if we follow it down the forearm, you can see it gives off four tendons. You’ve got these four tendons coming off the extensor digitorum. They run on the dorsum of the hand and insert onto the base of the middle and distal phalanx of these four digits – the index, middle, ring and little fingers.

DIVIDES INTO FOUR SLIPS

https://en.wikipedia.org/wiki/Extensor_digitorum_longus_muscle

The muscle passes under the superior and inferior extensor retinaculum of foot in company with the fibularis tertius, and divides into four slips, which run forward on the dorsum of the foot, and are inserted into the second and third phalanges of the four lesser toes.

DIVIDES INTO FOUR TENDONS

https://en.wikipedia.org/wiki/Extensor_digitorum_brevis_muscle

Course: fibres pass obliquely forwards and medially cross dorsum of foot and end in four tendons. The medial part of muscle ends in tendon which crosses the dorsalis pedis artery, inserts into dorsal surface base of PPX of great toe and is termed extensor hallucis brevis. The other three tendons insert into lateral sides of tendon of extensor digitorum longus which insert into the 2nd, 3rd and 4th toes.

THREE INSTEAD OF FOUR

https://www.physio-pedia.com/Hallux_Valgus

The Hallux or first toe, is the medio-distal part of the foot. It is formed by the first metatarsal (articulates with two sesamoid bones), the first proximal phalanx and the first distal phalanx. So the hallux is formed by three bones instead of four, unlike the other toes who have an extra bone called the intermediate phalanx.

FOUR TYPES

https://www.physio-pedia.com/Hallux_Valgus

The Manchester scale consists of standardized photographs of four types of hallux valgus: none, mild, moderate and severe. Research has shown that this scale is reliable in terms of both re-test and inter-tester reliability (kappa values of 0.77 and 0.86).

FOUR PARTS

 

Metatarsal Fractures

The metatarsals are the long bones between your toes and the middle of your foot. Each metatarsal has the following four parts:

http://orthoinfo.aaos.org/topic.cfm?topic=a00165

Head—which makes a joint with the base of the toe

Neck—the narrow area between the head and the shaft

Shaft—the long part of the bone

Base—which makes a joint with the midfoot

Distal Group

 

In the distal row, there are four tarsal bones – the cuboid and the three cuneiforms. These bones articulate with the metatarsals of the foot.

 

The cuboid is the most lateral bone in the distal row, articulating with the calcaneus posteriorly, and two metatarsals anteriorly. As the name suggests, it is shaped like a cube. The inferior surface of the cuboid is marked by a groove for the fibularis longus muscle.

 

The three cuneiforms (lateral, intermediate and medial) are wedge shaped bones. They articulate with the navicular posteriorly, and the metatarsals anteriorly. The shape of the bones helps form a transverse arch across the foot.

 

http://teachmeanatomy.info/lower-limb/bones/bones-of-the-foot-tarsals-metatarsals-and-phalanges/

MOST BIRDS FOUR TOES

https://en.wikipedia.org/wiki/Bird_feet_and_legs

Most birds have four toes (digits), typically three facing forward and one pointing backward.[3][4][8] In a typical perching bird they consist respectively of 3, 4, 5 and 2 phalanges.[2] Some birds have only the three forward-facing toes (tridactyl, for example the sanderling[2]) and the ostrich has only two toes (didactyl[2]).[5] The first digit, called the hallux, is homologous to the human big toe[3][4] and usually projects to the rear.[3][4][5]

MOSTLY PEOPLE ARE TAUGHT ABOUT THE THREE OSSICLES OF THE EAR THE MALLEUS INCUS AND STAPES BUT THERE IS A FOURTH TRANSCENDENT OSSICLE

https://en.wikipedia.org/wiki/Sesamoid_bone

In the ear—the lenticular process of the incus is a sesamoid bone and therefore is considered the fourth ossicle of the middle ear.

THE TRANSCENDENT FOURTH OSSICLE

https://en.wikipedia.org/wiki/Incus

The final part of the long limb, was once described as a "fourth ossicle" by Pieter Paaw in 1615.[8]

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FOUR PRONGED FOURTH TIME FOURTH IS DIFFERENT

https://en.wikipedia.org/wiki/Ornithischia

The ornithischian pelvis is "opisthopubic" meaning that the pubis points down and back (posterior) parallel with the ischium (Figure 1a).[2] Additionally, the pelvis has a forward-pointing process to support the abdomen.[2] This results in a four-pronged pelvic structure. In contrast to this, the saurischian pelvis is "propubic" meaning the pubis points toward the head (anterior), as in ancestral reptiles (Figure 1b).[2]

 

The opisthopubic pelvis independently evolved at least three times in dinosaurs (in ornithischians, birds and therizinosauroids).[9] Some argue that the opisthopubic pelvis evolved a fourth time in the clade Dromaeosauridae but this is controversial as other authors argue that dromeosaurids are mesopubic.[9]

three prongued v for prongued transcendenr
https://en.m.wikipedia.org/wiki/Saurischia
Saurischian dinosaurs are traditionally distinguished from ornithischian dinosaurs by their three-pronged pelvic structure, with the pubis pointed forward. The ornithischians' pelvis is arranged with the pubis rotated backward, parallel with the ischium, often also with a forward-pointing process, giving a four-pronged structure. The saurischian hip structure led Seeley to name them "lizard-hipped" dinosaurs, because they retained the ancestral hip anatomy also found in modern lizards and other reptiles.

the two major groups of dinosaurs are mainly distinguished by pelvic girdles on basis

of three pronged or four pronged the fynamic between three and four

 

https://books.google.com/books?id=_H3JotLS-rMC&pg=PA5&lpg=PA5&dq=four+pronged+pelvis&source=bl&ots=3_EdA_y_l2&sig=z43A8mt4prwHyveSGwcPDJgTVvk&hl=en&sa=X&ved=0ahUKEwjfm_TAv7XVAhUrw1QKHWI4ArMQ6AEIMjAC#v=onepage&q=four%20pronged%20pelvis&f=false

quadrant

tetra is four

http://onlinelibrary.wiley.com/doi/10.1111/j.1095-8312.1975.tb00731.x/abstract

Their conidia are hyaline and mostly of unusual form. In many the conidium is tetraradiate consisting of four long arms diverging from a common point. In the different genera the tetraradiate conidium develops in very different ways. In some it is a phialoconidium; in others a thalloconidium. In some attachment to the conidiophore is by the tip of one of the four arms; in others near their point of divergence. In some all arms develop simultaneously; in others in succession. The wide range of developmental geometry suggests convergent evolution. The tetraradiate aquatic spore also occurs in Basidiomycetes. The only two higher Basidiomycetes (both marine) with submerged sporophores have tetraradiate basidiospores. The world-wide distribution of aquatic Hyphomycetes is discussed. Their general ecology is also considered. Concentrations of 1000 to 10,000 conidia per litre may be reached in small rivers in autumn. Attention is paid to the possible biological value of the tetraradiate aquatic spore. The evidence suggests that this is connected with the problem of initial anchorage in the turbulent conditions of a stream.

https://en.m.wikipedia.org/wiki/Sensory_nervous_system

 

The receptors which react to the stimulus and initiate the process of sensation are commonly characterized in four distinct categories: chemoreceptors, photoreceptors, mechanoreceptors, and thermoreceptors.

FOUR MOST IMPORTANT SEX HORMONES

https://en.wikipedia.org/wiki/Human_sexuality

The four important sexual hormones are oxytocin, prolactin, follicle-stimulating hormone, and luteinizing hormone.[9][page

THERE IS THE TRANSCENDENT FOURTH LIGAMENT

https://en.wikipedia.org/wiki/Greater_omentum

Subdivisions[edit]

The greater omentum is often defined to encompass a variety of structures. Most sources include the following three:[2][3]

 

Gastrophrenic ligament—extends to the underside of the left dome of the diaphragm

Gastrocolic ligament—extends to the transverse colon (occasionally on its own considered synonymous with "greater omentum"[2])

Gastrosplenic ligament (or Gastrolienal) ligament)— extends to the spleen, overlying the kidney

FOUR CLASSICAL SUBMODALITIES

https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system

Gescheider et al., 1992; Greenspan and Lamotte, 1993). Of the four‘classical’ submodalities of the somatosensory system the tactileone subserves the perception of pressure, vibration, and texture,and relies upon four different receptors in the digit skin: (1)Pacinian corpuscles, (2) Meissner’s corpuscles, (3) Merkel’s disks,and (4) Ruffini endings, collectively known as low-thresholdmechanoreceptors (LTMs), a class of cutaneous receptors that are

 

The cutaneous sensory system (PDF Download Available). Available from: https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system [accessed Aug 6, 2017].

THE FOUR SUBMODALITIES OF CUTANEOUS SENSE

https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system

The cutaneous senses are traditionally thought to comprise four recognized submodalities that relay tactile, thermal, painful and pruritic (itch) information to the central nervous system,

 

The cutaneous sensory system (PDF Download Available). Available from: https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system [accessed Aug 6, 2017].

Quadrant

FOUR TYPES

https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system

Sensory axons are classified according to their degree ofmyelination, the fatty sheath that surrounds the nerve fiber. Thedegree of myelination determines the speed with which the axoncan conduct nerve impulses, and hence the nerve’s conductionvelocity. The largest and fastest axons are called Aa, and includesome of the proprioceptive neurons, such as the muscle stretchreceptors. The second largest group, called Ab, includes all of thediscriminative touch receptors being described here. Pain andtemperature include the third and fourth groups, A-dand C-fibers,and will be discussed in Section 2.2 (see Table 2).Vallbo and Johansson (1978) developed an electrophysiologicaltechnique called microneurography to study the function of singleperipheral nerve fibers innervating the human hand, which hasprovided a generally accepted model of touch that relates the fouranatomically defined types of cutaneous or subcutaneous senseorgans to their neural response patterns. Microneurographyinvolves inserting a fine tungsten microelectrode, tip diameter<5mm, through the skin of the wrist and into the underlying

 

The cutaneous sensory system (PDF Download Available). Available from: https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system [accessed Aug 6, 2017].

Quadrant

FOUR REGIONS PRIMARY SOMATOSENSORY CORTEX

https://www.researchgate.net/publication/223490107_The_cutaneous_sensory_system

Primary somatosensory cortex. SI,comprising four sub-regions (2, 1, 3a and 3b),

THERE ARE FOUR MITOCHONDRIAL COMPLEXES NOTICE THE REPEITITON OF FOURS IN EACH

https://en.wikipedia.org/wiki/Electron_transport_chain

REPETITION OF FOUR PROTONS IN COMPLEX 1

Four membrane-bound complexes have been identified in mitochondria. Each is an extremely complex transmembrane structure that is embedded in the inner membrane. Three of them are proton pumps. The structures are electrically connected by lipid-soluble electron carriers and water-soluble electron carriers. The overall electron transport chain:

 

 

In Complex I (NADH:ubiquinone oxidoreductase, NADH-CoQ reductase, or NADH dehydrogenase; EC 1.6.5.3), two electrons are removed from NADH and ultimately transferred to a lipid-soluble carrier, ubiquinone (Q). The reduced product, ubiquinol (QH2), freely diffuses within the membrane, and Complex I translocates four protons (H+) across the membrane, thus producing a proton gradient. Complex I is one of the main sites at which premature electron leakage to oxygen occurs, thus being one of the main sites of production of superoxide.[3]

 

The pathway of electrons is as follows:

 

NADH is oxidized to NAD+, by reducing Flavin mononucleotide to FMNH2 in one two-electron step. FMNH2 is then oxidized in two one-electron steps, through a semiquinone intermediate. Each electron thus transfers from the FMNH2 to an Fe-S cluster, from the Fe-S cluster to ubiquinone (Q). Transfer of the first electron results in the free-radical (semiquinone) form of Q, and transfer of the second electron reduces the semiquinone form to the ubiquinol form, QH2. During this process, four protons are translocated from the mitochondrial matrix to the intermembrane space. [4] As the electrons become continuously oxidized and reduced throughout the complex an electron current is produced along the 180 Angstrom width of the complex within the membrane. This current powers the active transport of four protons to the intermembrane space per two electrons from NADH.[5]

COMPLEX THREE FOUR PROTONS TRANSLOCATED AGAIN REPETITION OF FOUR

https://en.wikipedia.org/wiki/Electron_transport_chain

In Complex III (cytochrome bc1 complex or CoQH2-cytochrome c reductase; EC 1.10.2.2), the Q-cycle contributes to the proton gradient by an asymmetric absorption/release of protons. Two electrons are removed from QH2 at the QO site and sequentially transferred to two molecules of cytochrome c, a water-soluble electron carrier located within the intermembrane space. The two other electrons sequentially pass across the protein to the Qi site where the quinone part of ubiquinone is reduced to quinol. A proton gradient is formed by one quinol (2H+2e-) oxidations at the Qo site to form one quinone (2H+2e-) at the Qi site. (in total four protons are translocated: two protons reduce quinone to quinol and two protons are released from two ubiquinol molecules).

COMPLEX FOUR FOUR PROTONS TRANSLOCATED

https://en.wikipedia.org/wiki/Electron_transport_chain

Complex IV[edit]

In Complex IV (cytochrome c oxidase; EC 1.9.3.1), sometimes called cytochrome AA3, four electrons are removed from four molecules of cytochrome c and transferred to molecular oxygen (O2), producing two molecules of water. At the same time, eight protons are removed from the mitochondrial matrix (although only four are translocated across the membrane), contributing to the proton gradient. The activity of cytochrome c oxidase is inhibited by cyanide.

FOUR ELECTRONS

https://en.wikipedia.org/wiki/Chemiosmosis

To generate one molecule of diatomic oxygen, 10 photons must be absorbed by photosystems I and II, four electrons must move through the two photosystems, and 2 NAPDH are generated (later used for carbon dioxide fixation in the Calvin Cycle).

MITOCHONDRION FOUR COMPARTMENTS

https://microbewiki.kenyon.edu/index.php/Mitochondria

The mitochondrion has four compartments: an outer membrane, an inner membrane (made of cardiolipin), an intermembrane space (between outer and inner membranes), and a matrix (inside inner membrane). The processes that happen in the mitochondron are pyruvate oxidation, the Krebs cycle, the metabolism of amino acids, fatty acids, and steroids, and generation of adenosine triphosphate (ATP). ATP, which is used for energy, is made through the electron-transport chain and the oxidative-phosphoylation system (respiratory chain) in the inner mitochondrial membrane. (WUSTL) View an animated diagram of the proton pump and ATP synthesis from WUSTL. Notice the folds, or cristae, that adds surface area to the mitochondrial inner membrane on the picture and diagram to the right.

four main cellular compartments
https://en.m.wikipedia.org/wiki/Cellular_compartment
In general there are 4 main cellular compartments, they are:

The nuclear compartment comprising the nucleus
The intercisternal space which comprises the space between the membranes of the endoplasmic reticulum (which is continuous with the nuclear envelope)
Organelles (the mitochondrion in all eukaryotes and the plastid in phototrophic eukaryotes)
The cytosol

FOUR MAJOR NEUROENDOCRINE SYSTEMS

https://en.wikipedia.org/wiki/Hypothalamic–pituitary–adrenal_axis

The HPA axis, HPG axis, HPT axis, and the hypothalamic–neurohypophyseal system are the four major neuroendocrine systems through which the hypothalamus and pituitary direct neuroendocrine function.[1]

T3 and T4 THE DYNAMIC BETWEEN THREE AND FOUR

https://en.wikipedia.org/wiki/Hypothalamic–pituitary–thyroid_axis

The hypothalamus senses low circulating levels of thyroid hormone (Triiodothyronine (T3) and Thyroxine (T4)) and responds by releasing thyrotropin-releasing hormone (TRH). The TRH stimulates the pituitary to produce thyroid-stimulating hormone (TSH). The TSH, in turn, stimulates the thyroid to produce thyroid hormone until levels in the blood return to normal. Thyroid hormone exerts negative feedback control over the hypothalamus as well as anterior pituitary, thus controlling the release of both TRH from hypothalamus and TSH from anterior pituitary gland.[2]

FOUR RESPIRATORY CENTERS- FOURTH DIFFERENT

https://en.wikipedia.org/wiki/Human_brain

The brain controls the rate of breathing, mainly by respiratory centres in the medulla and pons.[79] The respiratory centres control respiration, by generating motor signals that are passed down the spinal cord, along the phrenic nerve to the diaphragm and other muscles of respiration. This is a mixed nerve that carries sensory information back to the centres. There are four respiratory centres, three with a more clearly defined function, and an apneustic centre with a less clear function. In the medulla a dorsal respiratory group causes the desire to breathe in and receives sensory information directly from the body. Also in the medulla, the ventral respiratory group influences breathing out during exertion. In the pons the pneumotaxic centre influences the duration of each breath,[79] and the apneustic centre seems to have an influence on inhalation. The respiratory centres directly senses blood carbon dioxide and pH. Information about blood oxygen, carbon dioxide and pH levels are also sensed on the walls of arteries in the peripheral chemoreceptors of the aortic and carotid bodies. This information is passed via the vagus and glossopharyngeal nerves to the respiratory centres. High carbon dioxide, an acidic pH, or low oxygen stimulate the respiratory centres.[79] The desire to breathe in is also affected by pulmonary stretch receptors in the lungs which, when activated, prevent the lungs from overinflating by transmitting information to the respiratory centres via the vagus nerve.[79]

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THEORY FOUR MAIN LINEAGES OF BO

https://en.wikipedia.org/wiki/ABO_blood_group_system

Some evolutionary biologists theorize that the IA allele evolved first, followed by O (by the deletion of a single nucleotide, shifting the reading frame) and then IB.[citation needed] This chronology accounts for the percentage of people worldwide with each blood type. It is consistent with the accepted patterns of early population movements and varying prevalent blood types in different parts of the world: for instance, B is very common in populations of Asian descent, but rare in ones of Western European descent. Another theory states that there are four main lineages of the ABO gene and that mutations creating type O have occurred at least three times in humans.[34] From oldest to youngest, these lineages comprise the following alleles: A101/A201/O09, B101, O02 and O01. The continued presence of the O alleles is hypothesized to be the result of balancing selection.[34] Both theories contradict the previously held theory that type O blood evolved first.[citation needed]

DIFFERENT PEOPLE ON THE FOUR HUMOURS

https://www.nlm.nih.gov/exhibition/shakespeare/fourhumors.html

above left: Aristotle, De Animalibus, ca 1225. Courtesy National Library of Medicine. Greek philosopher Aristotle (384 BCE–322 BCE) identified the classic four elements—earth, water, air, and fire—as the building blocks of the universe. CLICK FOR PORTRAIT OF ARISTOTLE.

 

above center: Hippocrates, De Humoribus, 1525. Courtesy National Library of Medicine. Greek physician Hippocrates (ca. 460 BCE–370 BCE) is often credited with developing the theory of the four humors—blood, yellow bile, black bile, and phlegm—and their influence on the body and its emotions. His famous treatise on Airs, Waters, and Places describes the influence of geography on the body and its humoral makeup. CLICK FOR PORTRAIT OF HIPPOCRATES.

 

above right: Galen, De temperamentis libri tres, 1545. Courtesy National Library of Medicine. Born in Pergamon, Roman physician and philosopher Galen (ca. 131–ca. 201) described the four temperaments as determined by a balance of the qualities of hot, cold, moist, and dry. He was revered as a great clinician. CLICK FOR PORTRAIT OF GALEN.

 

Scanned pages of the book, Optick Glasse of Humors, open to pages 76 and 77 where Chapter VI of Temperaments starts.

left: Thomas Walkington, Optick Glasse of Humors, 1639. Courtesy National Library of Medicine. The “glasse” in the title of University of Cambridge cleric Thomas Walkington’s Optick Glasse of Humors is a mirror. The reader is promised greater self-knowledge through understanding the role of the four bodily humors in determining individual human behaviors and overall disposition. For readers of Walkington’s text, “temperament” (what we would call personality) was literally a matter of temperature—the result of the action of cold, hot, wet, and dry in governing behavior.

FOUR SPECIES

https://en.wikipedia.org/wiki/Toxopneustes_pileolus

Toxopneustes pileolus is one of four species belonging to the genus Toxopneustes. It belongs to the family Toxopneustidae in the order Camarodonta. It was originally described as Echinus pileolus by the French naturalist Jean-Baptiste Lamarck in 1816, in the second book of his Histoire naturelle des animaux sans vertèbres series. It was later used as the type species for the newly created genus Toxopneustes by the Swiss American biologist Louis Agassiz.[1]

https://en.wikipedia.org/wiki/Na%2B/K%2B-ATPase

All mammals have four different sodium pump sub-types, or isoforms, that each has unique properties and tissue expression patterns

T3T4 THE DYNAMIC BETWEEN THREE AND FOUR

https://en.wikipedia.org/wiki/Thyroid_hormones

The thyroid hormones, triiodothyronine (T3) and its prohormone, thyroxine (T4), are tyrosine-based hormones produced by the thyroid gland that are primarily responsible for regulation of metabolism. T3 and T4 are partially composed of iodine (see molecular model). A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3.[1] In humans, the ratio of T4 to T3 released into the blood is between 14:1 and 20:1. T4 is converted to the active T3 (three to four times more potent than T4) within cells by deiodinases (5'-iodinase). These are further processed by decarboxylation and deiodination to produce iodothyronamine (T1a) and thyronamine (T0a). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T3 production. Edward Calvin Kendall was responsible for the isolation of thyroxine in 1915.[2]

THE NEURAL TUBE DIVIDED INTO FOUR SECTIONS

https://en.wikipedia.org/wiki/Cerebrum

In the developing vertebrate embryo, the neural tube is subdivided into four unseparated sections which then develop further into distinct regions of the central nervous system; these are the prosencephalon (forebrain), the mesencephalon (midbrain) the rhombencephalon (hindbrain) and the spinal cord

FOUR NEURAL TUBE SUBDIVISIONS

https://en.wikipedia.org/wiki/Neural_tube

Four neural tube subdivisions each eventually develop into distinct regions of the central nervous system by the division of neuroepithelial cells: the forebrain (prosencephalon), the midbrain (mesencephalon), the hindbrain (rhombencephalon) and the spinal cord.

 

The prosencephalon further goes on to develop into the telencephalon (cerebrum) and the diencephalon (the optic vesicles and hypothalamus).

The mesencephalon stays as the midbrain.

The rhombencephalon develops into the metencephalon (the pons and cerebellum) and the myelencephalon (the medulla oblongata).

Shh secreted from the floor plate creates a gradient along the ventral neural tube. Shh functions in a concentration-dependent manner to specify ventral neuronal fates. V0-V3 represent four different classes of ventral interneurons, and MN indicates motor neurons.

FOUR STEPS PRIMARY NEURALATION FOUR STAGES NEURAL PLATE AND NUERAL TUBE FORMATION

https://en.wikipedia.org/wiki/Neural_plate

Generally divided into four steps, the process of primary neurulation involves the neural plate in the first three. The formation and folding of the neural plate is the first step in primary neurulation. This is followed by the refinement and growth of neural plate cells. The third step of primary neurulation does not involve the neural plate per se, but rather the edges of the neural plate, which come together, turning the plate into the start of the neural tube. With the neural plate having folded into a tube, the neural folds come together to complete the fusion of the neural tube. This process is illustrated in the figure to the right, where the neural plate is shown in purple. The lime green marks the edges of the neural plate, which become the neural folds, involved in the folding of the plate to create the neural tube. The figure demonstrates the development of the neural plate into the neural tube, which is where the neural crest cells are derived from as well.[1]

 

There are four stages of neural plate and neural tube formation: formation, bending, convergence, and closure. The formation of the neural plate starts when dorsal mesoderm signals ectodermal cells above it to lengthen into columnar neural plate cells.[4] This different shape distinguishes the cells of the presumptive neural plate from other pre-epidermal cells. If the neural plate is separated by itself, it will still develop to make a thinner plate but will not form a neural tube. If the region containing presumptive epidermis and neural plate tissue is isolated, small neural folds will form. Elongation that occurs throughout the formation of the neural plate and closure of the neural tube is vital; the closing areas of the neural tube are seen to have very increased elongation activity in the midline compared to already closed areas when the plate was beginning to shape itself into a tube.[5]

FOUR CELL DIVISIONS AND THEN 16 CELL MORULA- 16 SQUARES QMR

https://en.wikipedia.org/wiki/Embryogenesis

Cell division with no significant growth, producing a cluster of cells that is the same size as the original zygote, is called cleavage. At least four initial cell divisions occur, resulting in a dense ball of at least sixteen cells called the morula. The different cells derived from cleavage, up to the blastula stage, are called blastomeres. Depending mostly on the amount of yolk in the egg, the cleavage can be holoblastic (total) or meroblastic (partial)[1].

MACROMERES QUADRANTS AND QUARTETS

https://en.wikipedia.org/wiki/Cleavage_(embryo)

Spiral cleavage is conserved between many members of the lophotrochozoan taxa, referred to as Spiralia.[3] Most spiralians undergo equal spiral cleavage, although some undergo unequal cleavage (see below).[4] This group includes annelids, molluscs, and sipuncula. Spiral cleavage can vary between species, but generally the first two cell divisions result in four macromeres, also called blastomeres, (A, B, C, D) each representing one quadrant of the embryo. These first two cleavages are oriented in planes that occur at right angles parallel to the animal-vegetal axis of the zygote.[3] At the 4-cell stage, the A and C macromeres meet at the animal pole, creating the animal cross-furrow, while the B and D macromeres meet at the vegetal pole, creating the vegetal cross-furrow.[5] With each successive cleavage cycle, the macromeres give rise to quartets of smaller micromeres at the animal pole.[6][7] The divisions that produce these quartets occur at an oblique angle, an angle that is not a multiple of 90°, to the animal-vegetal axis.[7] Each quartet of micromeres is rotated relative to their parent macromere, and the chirality of this rotation differs between odd and even numbered quartets, meaning that there is alternating symmetry between the odd and even quartets.[3] In other words, the orientation of divisions that produces each quartet alternates between being clockwise and counterclockwise with respect to the animal pole.[7] The alternating cleavage pattern that occurs as the quartets are generated produces quartets of micromeres that reside in the cleavage furrows of the four macromeres.[5] When viewed from the animal pole, this arrangement of cells displays a spiral pattern.

 

D quadrant specification through equal and unequal cleavage mechanisms. At the 4-cell stage of equal cleavage, the D macromere has not been specified yet. It will be specified after the formation of the third quartet of micromeres. Unequal cleavage occurs in two ways: asymmetric positioning of the mitotic spindle, or through the formation of a polar lobe (PL).

Specification of the D macromere and is an important aspect of spiralian development. Although the primary axis, animal-vegetal, is determined during oogenesis, the secondary axis, dorsal-ventral, is determined by the specification of the D quadrant.[7] The D macromere facilitates cell divisions that differ from those produced by the other three macromeres. Cells of the D quadrant give rise to dorsal and posterior structures of the spiralian.[7] Two known mechanisms exist to specify the D quadrant. These mechanisms include equal cleavage and unequal cleavage.

In equal cleavage, the first two cell divisions produce four macromeres that are indistinguishable from one another. Each macromere has the potential of becoming the D macromere.[6] After the formation of the third quartet, one of the macromeres initiates maximum contact with the overlying micromeres in the animal pole of the embryo.[6][7] This contact is required to distinguish one macromere as the official D quadrant blastomere. In equally cleaving spiral embryos, the D quadrant is not specified until after the formation of the third quartet, when contact with the micromeres dictates one cell to become the future D blastomere. Once specified, the D blastomere signals to surrounding micromeres to lay out their cell fates.[7]

In unequal cleavage, the first two cell divisions are unequal producing four cells in which one cell is bigger than the other three. This larger cell is specified as the D macromere.[6][7] Unlike equally cleaving spiralians, the D macromere is specified at the four-cell stage during unequal cleavage. Unequal cleavage can occur in two ways. One method involves asymmetric positioning of the cleavage spindle.[7] This occurs when the aster at one pole attaches to the cell membrane, causing it to be much smaller than the aster at the other pole.[6] This results in an unequal cytokinesis, in which both macromeres inherit part of the animal region of the egg, but only the bigger macromere inherits the vegetal region.[6] The second mechanism of unequal cleavage involves the production of an enucleate, membrane bound, cytoplasmic protrusion, called a polar lobe.[6] This polar lobe forms at the vegetal pole during cleavage, and then gets shunted to the D blastomere.[5][6] The polar lobe contains vegetal cytoplasm, which becomes inherited by the future D macromere.[7]

QUARTETS MACROMERES

https://en.wikipedia.org/wiki/File:Equal_vs_unequal_cleavage.jpg

https://en.wikipedia.org/wiki/Cleavage_(embryo)

D quadrant specification through equal and unequal cleavage mechanisms. At the 4-cell stage of equal cleavage, the D macromere has not been specified yet. It will be specified after the formation of the third quartet of micromeres. Unequal cleavage occurs in two ways: asymmetric positioning of the mitotic spindle, or through the formation of a polar lobe (PL).

THE FOUR PATTERNS OF BILATERAL CLEAVAGE

 

There are four different patterns of holoblastic cleavage for isolecithal cells. The first is bilateral cleavage. This is when cleavage activity is the same on both sides, creating left and right halves. We can see the same type of symmetry in ourselves: look in a mirror and draw a line down your middle, and you'll find that each side is a mirror image of the other. We see this type of cleavage in animals such as tunicates, which, although they look nothing like us, are our primitive chordate ancestors.

 

Tunicates experience bilateral cleavage.

tunicate

The second pattern is radial cleavage, which is when cleavage occurs radially around a central axis. Think of the spokes on a wheel radiating from the center, or slices of pizza in a whole pie, and you'll get the idea here. We see this type of cleavage in animals such as echinoderms (sea stars, sea urchins, etc.), which interestingly enough, are radially symmetric as fully developed organisms.

 

The third pattern for isolecithal cells is called rotational cleavage, and this happens when there is a rotation of the cleavage plane. This is quite interesting, because the first division occurs normally. But then things change a bit because one of these new cells splits length-wise while the other splits width-wise. It's rotated 90 degrees to the first one, hence the name rotational cleavage! This is the very cleavage that we humans (and other mammals) undergo.

 

The final pattern for isolecithal cells is spiral cleavage. This is when cleavage occurs in a spiral pattern around an axis. Basically, if you were looking down from the top you would see the newly divided cells 'spiraling' around an axis that runs right down the middle, much like looking down a spiral staircase from the top. Instead of being either horizontally or vertically oriented, the cleavage plane slants around this vertical axis. We see this type of cleavage in animals like molluscs. Interestingly, if you compare the spiral shape of a snail's shell (a snail is a mollusc), you'll see this same beautiful pattern!

 

http://study.com/academy/lesson/holoblastic-cleavage-definition-patterns.html

https://en.wikipedia.org/wiki/Cleavage_(embryo)

Quadrant

https://en.wikipedia.org/wiki/Cell_adhesion_molecule

Most of the CAMs belong to four protein families: Ig (immunoglobulin) superfamily (IgSF CAMs), the integrins, the cadherins, and the selectins.

FOUR PHASES

https://en.wikipedia.org/wiki/Bacteria

Bacterial growth follows four phases. When a population of bacteria first enter a high-nutrient environment that allows growth, the cells need to adapt to their new environment. The first phase of growth is the lag phase, a period of slow growth when the cells are adapting to the high-nutrient environment and preparing for fast growth. The lag phase has high biosynthesis rates, as proteins necessary for rapid growth are produced.[106] The second phase of growth is the log phase, also known as the logarithmic or exponential phase. The log phase is marked by rapid exponential growth. The rate at which cells grow during this phase is known as the growth rate (k), and the time it takes the cells to double is known as the generation time (g). During log phase, nutrients are metabolised at maximum speed until one of the nutrients is depleted and starts limiting growth. The third phase of growth is the stationary phase and is caused by depleted nutrients. The cells reduce their metabolic activity and consume non-essential cellular proteins. The stationary phase is a transition from rapid growth to a stress response state and there is increased expression of genes involved in DNA repair, antioxidant metabolism and nutrient transport.[107] The final phase is the death phase where the bacteria run out of nutrients and die.

FOUR GROUPS

https://en.wikipedia.org/wiki/Bacteria

The Gram stain, developed in 1884 by Hans Christian Gram, characterises bacteria based on the structural characteristics of their cell walls.[70] The thick layers of peptidoglycan in the "gram-positive" cell wall stain purple, while the thin "gram-negative" cell wall appears pink. By combining morphology and Gram-staining, most bacteria can be classified as belonging to one of four groups (gram-positive cocci, gram-positive bacilli, gram-negative cocci and gram-negative bacilli). Some organisms are best identified by stains other than the Gram stain, particularly mycobacteria or Nocardia, which show acid-fastness on Ziehl–Neelsen or similar stains.[153] Other organisms may need to be identified by their growth in special media, or by other techniques, such as serology.

https://en.wikipedia.org/wiki/Medicine

Four actions are the basis of physical examination: inspection, palpation (feel), percussion (tap to determine resonance characteristics), and auscultation (listen), generally in that order although auscultation occurs prior to percussion and palpation for abdominal assessments.[13]

Linear Tetrad of Megaspores:

http://www.biologydiscussion.com/embryology/top-16-stages-of-embryology-in-plants-with-diagram/34153

1. Four megaspores are arranged in linear fashion.

 

2. These are haploid in nature.

 

3. Out of the four megaspores, only one remains func­tional which is near the chalazal end. Remaining three degenerate (Fig. 190).

POLLEN TETRADS

http://www.biologydiscussion.com/embryology/top-16-stages-of-embryology-in-plants-with-diagram/34153

Embryology in Plants: Stage # 4.

 

Pollen Tetrads:

 

(A) Isobilateral Tetrad:

 

All the four spores are formed in one plane because the spindles of first and sec­ond meiotic division remain at right angle to one another (Fig. 184), e.g.,Zea mays.

 

Pollen Tetrads

 

(B) Decussate Tetrad:

 

Out of the two lower spores, only one is visible. Both the upper ones are clear (Fig. 184), e.g.,Magnolia.

 

(C) T-shaped Tetrad:

 

In meiosis II upper cell divides to form two cells present side by side and the lower cell forms two cells lying one above the other, e.g., Aristolochia.

 

(D) Linear Tetrad:

 

All the four spores are present one above the other in a linear fashion, e.g., Halophila.

Embryology in Plants: Stage # 2.

http://www.biologydiscussion.com/embryology/top-16-stages-of-embryology-in-plants-with-diagram/34153

T.S. Anther Showing Four Mature Pollen Sacs:

http://cdn.biologydiscussion.com/wp-content/uploads/2016/05/clip_image004-197.jpg

1. It is a four-cornered structure containing a pollen sac (Fig. 182).

FOUR NUCLEI EMBRYO SAC

http://www.biologydiscussion.com/embryology/top-16-stages-of-embryology-in-plants-with-diagram/34153

Embryology in Plants: Stage # 12.

 

Ovule with 4-Nucleate Embryo-Sac:

 

FourNucleate Embryo-Sac

 

1. Four nuclei are present in the embryo sac (Fig. 192).

 

2. Out of the four nuclei, two are present near the chalazal end and the remaining two nuclei near the micropylar end.

 

3. In the centre is present a large central vacuole.

 

4. Traces of degenerated megaspores are also seen at the micropylar end.

FOUR SOLID LOBES QUADRIGA QUAD IS FOUR

https://en.wikipedia.org/wiki/Midbrain

The corpora quadrigemina ("quadruplet bodies") are four solid lobes on the dorsal side of the cerebral aqueduct, where the superior posterior pair are called the superior colliculi and the inferior posterior pair are called the inferior colliculi. The homologous structures are called optic lobes in some lower vertebrates (fishes and amphibians) where they integrate sensory information from the eyes and certain auditory reflexes.[4][5]

 

The four solid lobes help to decussate several fibres of the optic nerve. However, some fibers also show ipsilateral arrangement (i.e., they run parallel on the same side without decussating.)

FOUR CATEGORIES

https://en.wikipedia.org/wiki/Putamen

Seven participants with basal ganglia lesions were used in the experiment, along with nine control participants. It is important to note that the caudate was not affected. The participants were tested for each type of learning during separate sessions, so the information processes would not interfere with each other. During each session, participants sat in front of a computer screen and various lines were displayed. These lines were created by using a randomization technique where random samples were taken from one of four categories. For ruled-based testing, these samples were used to construct lines of various length and orientation that fell into these four separate categories. After the stimulus was displayed, the subjects were asked to press 1 of 4 buttons to indicate which category the line fell into. The same process was repeated for information-integration tasks, and the same stimuli were used, except that the category boundaries were rotated 45°. This rotation causes the subject to integrate the quantitative information about the line before determining what category it is in.

FOUR KINDS

https://bmcstructbiol.biomedcentral.com/articles/10.1186/1472-6807-5-14

The Ramachandran plot is a fundamental tool in the analysis of protein structures. Of the 4 basic types of Ramachandran plots, the interactions that determine the generic and proline Ramachandran plots are well understood. The interactions of the glycine and pre-proline Ramachandran plots are not.

FUOR TYPES OF RAMACHANDRAN PLOT

https://bmcstructbiol.biomedcentral.com/articles/10.1186/1472-6807-5-14

The Ramachandran plot [1] is the 2d plot of the φ-ψ torsion angles of the protein backbone. It provides a simple view of the conformation of a protein. The φ-ψ angles cluster into distinct regions in the Ramachandran plot where each region corresponds to a particular secondary structure. There are four basic types of Ramachandran plots, depending on the stereo-chemistry of the amino acid: generic (which refers to the 18 non-glycine non-proline amino acids), glycine, proline, and pre-proline (which refers to residues preceding a proline [2]). The generic and proline Ramachandran plots are now well understood [3] but the glycine and pre-proline Ramachandran plots are not.

FOUR GENERA IN HOMINADAE

http://www.pnas.org/content/100/13/7684/F1.expansion.html

The new fossil findings warrant two conclusions: first, the diversity of lineages among very early hominids is greater than previously believed; moreover, their geographical range has been expanded with the discovery of Sahelanthropus from Chad, west-central Africa. Nevertheless, and until new evidence makes it possible to decide on the degree of bipedalism of Orrorin, Sahelanthropus, and Ardipithecus, a parsimonious option would be to retain only four genera in Hominidae: Praeanthropus, Ardipithecus, Australopithecus, and Homo (plus one genus incertae sedis, whose definitive status can only later be determined) (Fig. 1). A tentative outline of hominid evolution involving four major (genus-determining) episodes is shown in Table 1.

FOUR GENERA HOMINIDAE

http://www.pnas.org/content/100/13/7684.full

Phylogeny of the genera belonging to the Hominid family. Four different genera are proposed, corresponding to four kinds of adaptation. The genus Praeanthropus (formerly named Australopithecus) evolved incipient bipedalism on the ground of tropical forests. The genus Ardipithecus evolved a dietary adaptation that developed thin molar enamel, similar to that of the African great apes. The genus Australopithecus (formerly also named Paranthropus) exploited hard vegetal resources of the savanna by developing a robust masticatory apparatus. The genus Homo retained gracile maxillae and dentition and later initiated the development of larger crania and cultural adaptation to the savanna by means of lithic industries. The proposed names follow the rules of taxonomy, favoring the names given initially, when the first taxon of the genus was established. The phylogenetic location and taxonomic classification of Sahelanthropus are uncertain. Pairs of Homo taxa separated by a slash represent closely related (or, according to some authors, the same) species. An asterisk marks each species germinalis, i.e., originating a genus.

FOUR SPECIES

https://en.wikipedia.org/wiki/Proconsul_(primate)

https://en.wikipedia.org/wiki/Proconsul_(primate)

Proconsul is an extinct genus of primates that existed from 23 to 25 million years ago during the Miocene epoch. Fossil remains are present in Eastern Africa including Kenya and Uganda. Four species have been classified to date: P. africanus, P. gitongai, P. major and P. meswae. The four species differ mainly in body size. Environmental reconstructions for the Early Miocene Proconsul sites are still tentative and range from forested environments to more open, arid grasslands.

FOUR TYPES CYTOPLASMIC RRNA

https://en.wikipedia.org/wiki/Ribosomopathy

The products of this processing within the cell nucleus are the four principal types of cytoplasmic rRNA: 28S, 5.8S, 18S, and 5S subunits.[10]:

As an example, tRNAAla encodes four different tRNA isoacceptors (AGC, UGC, GGC and CGC)

https://en.wikipedia.org/wiki/Transfer_RNA#Anticodon

There are at least four structural types of tRFs believed to originate from mature tRNAs, including the relatively long tRNA halves and short 5’-tRFs, 3’-tRFs and i-tRFs.[31][35][36]

 

At the system or the organismal level, the four types of tRFs have a diverse spectrum of activities. Functionally, tRFs are associated with viral infection,[42] cancer,[35][36] cell proliferation [37] and also with epigenetic transgenerational regulation of metabolism.[

 

In the genetic code, it is common for a single amino acid to be specified by all four third-position possibilities, or at least by both pyrimidines and purines; for example, the amino acid glycine is coded for by the codon sequences GGU, GGC, GGA, and GGG.

TRNA IS THE CROSS

https://www.thecatholicthing.org/2015/04/02/bread-and-wine/

It would require a lot more space to describe the adequate details, but briefly, if one is familiar with the manner in which DNA transfers its coded information out of the nucleus of the cell into the main "body" of the cell to form proteins, which are the "building blocks" of living matter, the correlation to Christ's role in the world seems almost undeniable.

 

For the "coded information" (in the form of "messenger RNA strands" -- mRNA for short -- derived from the raw DNA in the nucleus) travels out of the nucleus where it is acted upon by what is called "transfer RNA" -- again tRNA for short). This tRNA takes a sequences of "three-letter" strings (essentially abstract coded information) from the mRNA (typically shown at the "top" of the molecule in diagrams) and converts it into amino acids (typically shown at the "bottom" of the molecule in diagrams). The amino acids then get strung together to form the proteins or physical building blocks of the cell.

 

Analogously, one might say the tRNA is taking the coded "heavenly spiritual essence" of DNA (from "above", as the scientific diagrams nearly always show) and turning it into the "physical body and blood here on earth" of the cell (down "below", as shown in those same diagrams). This is essentially what Christ in his Incarnation and establishment of the Eucharist did by bringing God's presence to us.

 

But here is the visual kicker -- the schematic diagrams of the tRNA molecule (you can look up images of "tRNA" on Bing or Google) have a distinct "cross-shaped" appearance showing the "abstract coded DNA information" attached at the "top" of the cross, and the amino acid protein "building blocks" at the bottom of the cross. And for a bit of textual gravy, the very identifier for the specific form of RNA in "tRNA" is a lower case "t" -- the one letter in our alphabet that most looks like a cross itself.

 

Again, a very simplified description, and we must, I suppose, look on those schematic diagram and naming convention "appearances" as happy coincidences. But to me they are simply delicious to look upon and contemplate.

https://en.wikipedia.org/wiki/Blast_injury

 

Blast injuries are divided into four classes: primary, secondary, tertiary, and quaternary.

FOUR SECTIONS LARGE INTESTINE

https://en.wikipedia.org/wiki/Large_intestine

The ascending colon is the first of four sections of the large intestine. It is connected to the small intestine by a section of bowel called the cecum. The ascending colon runs upwards through the abdominal cavity toward the transverse colon for approximately eight inches (20 cm).

FOUR LOBES OF THE LIVER

https://www.ece.ncsu.edu/imaging/MedImg/SIMS/GE1_3.html

There are, on the surface, four lobes: right, left, caudate and quadrate. The Falciform ligament divides the liver into two main lobes, right and left, with the right lobe being the larger and is sub- divided into the right lobe proper, the caudate lobe and the quadrate lobe.

FOUR FS

https://www.ece.ncsu.edu/imaging/MedImg/SIMS/GE1_3.html

They are rare in the first two decades of life. The four F's fat, female, fertile (multiparous), and forty characterize the population with the highest incidence. Although gallstones may form anywhere in the biliary tract, the majority are found in the gallbladder. In about 80 percent of cases cholesterol is the chief component of gallstones. Cholesterol stones are classically 1 to 5 cm. in diameter, pale yellow, round or oval and often translucent. Also found are pigment stones composed of calcium bilirubin. These stones are usually associated with a hemolytic disorder. They are jet-black. Mixed stones contain calcium carbonate as well as calcium bilirubin.

FOUR LOBES

https://en.wikipedia.org/wiki/Liver

Gross anatomy traditionally divided the liver into two portions – a right and a left lobe, as viewed from the front (diaphragmatic) surface; but the underside (the visceral surface) shows it to be divided into four lobes and includes the caudate and quadrate lobes.[14]

 

The falciform ligament, visible on the front of the liver, divides the liver into a left and a much larger right lobe. From the visceral surface, the two additional lobes are located between the right and left lobes, one in front of the other. A line can be imagined running from the left of the vena cava and all the way forward to divide the liver and gallbladder into two halves.[15] This line is called "Cantlie's line".[16]

 

Other anatomical landmarks exist, such as the ligamentum venosum and the round ligament of the liver (ligamentum teres), which further divide the left side of the liver in two sections. An important anatomical landmark, the porta hepatis, also known as the transverse fissure of the liver, divides this left portion into four segments, which can be numbered starting at the caudate lobe as I in an anticlockwise manner. From this visceral view, seven segments can be seen, because the eighth segment is only visible in the parietal view.[17]

FOUR CATEGORIES DIABETES
https://en.wikipedia.org/wiki/Diabetes_mellitus
Diabetes mellitus is classified into four broad categories: type 1, type 2, gestational diabetes, and "other specific types".[8] The "other specific types" are a collection of a few dozen individual causes.[8] Diabetes is a more variable disease than once thought and people may have combinations of forms.[32] The term "diabetes", without qualification, usually refers to diabetes mellitus.

https://en.wikipedia.org/wiki/Lung#Left_lung

The four genes mostly associated with branching morphogenesis in the lung are the intercellular signalling protein – sonic hedgehog (SHH), fibroblast growth factors FGF10 and FGFR2b, and bone morphogenetic protein BMP4. FGF10 is seen to have the most prominent role. FGF10 is a paracrine signalling molecule needed for epithelial branching, and SHH inhibits FGF10.[23][24] The development of the alveoli is influenced by a different mechanism whereby continued bifurcation is stopped and the distal tips become dilated to form the alveoli.

Some species of spider have four pairs of book lungs but most have two pairs.

https://en.wikipedia.org/wiki/Lung#Left_lung

Two such events would have produced four homologous genes, one of which must have been lost

https://en.wikipedia.org/wiki/Hedgehog_signaling_pathway

FOUR MAJOR PARTS NEPHRON

http://www.kidneyhealthcare.com/2010/06/parts-of-nephron.html

The filtered fluid including wastes and other substances then pass through a very small tube called the renal tubule. It is a continuous tube, which has four major parts: the proximal tubule, descending loop, ascending loop and the distal tubule.

FOUR LAYERS

http://emedicine.medscape.com/article/1948929-overview

The greater omentum (gastrocolic ligament) is like an apron with 4 layers of peritoneum (often fused). Two layers go down from stomach and then run upward to be attached to the transverse colon.

http://www.laparoscopic.md/digestion/stomach

There are four main types of cells for stomach secretions spread all over the inner surface of the stomach:

 

Mucous cells secrete the alkaline mucous for shielding the epithelium from hydrochloric acid. These are found in the fundic, cardiac, and pyloric region.

Parietal cells, located in the fundic, cardiac, and pyloric region, secrete hydrochloric acid; the acid activates release of pepsin for protein digestion. The acid also kills micro-organisms swallowed with the food.

Chief cells secrete pepsin. These cells are located in the fundic region.

G cells are found in the fundic, pyloric, and gastric region. These secrete gastrin which stimulates the secretion of hydrochloric acid.

FOUR LAYERS OF STOMACH SMALL INTESTINE AND LARGE INTESTINE QUADRANT PATTERN WHERE FOURTH IS DIFFERENT AND THIRD IS ACTION MUSCLE

https://socratic.org/questions/what-are-the-names-of-the-tissue-layers-of-the-stomach

Explanation:

The wall of stomach, like the other parts of the gastrointestinal tract, consists of four layers : Mucosa, Submucosa, Muscularis, Serosa.

http://www.cs.umb.edu/~marc/pubs/garaas_pomplun_bionetics2007.pdf

Therefore, there are four types of direction-sensitive ganglion cells in the network: left-sensitive, right-sensitive, up-sensitive, and down-sensitive. The different types of ganglion cells differ only by the location of their synaptic connections.

One ganglion cell of each type is placed directly beneath each amacrine cell in the network with the exception of cells on the edge of the network (i.e. right- and left-sensitive cells start under the fourth amacrine cell of each row and finish four cells away

FOUR PARTS NEURON

https://faculty.washington.edu/chudler/lesson1.html

Introduction: The brain is made up of about 100 billion nerve cells (also called "neurons"). A neuron has 4 basic parts: the dendrites, the cell body (also called the "soma"), the axon and the axon terminal.

Dendrites - Extensions from the neuron cell body that take information to the cell body. Dendrites usually branch close to the cell body.

Cell body (soma) - the part of the cell that contains the nucleus.

Axon - the extension from the neuron cell body that takes information away from the cell body. A single axon projects out of the cell body.

Axon terminal - end part of an axon that makes a synaptic contact with another cell.

THE FOURTH TYPE IS DIFFERENT

https://www.khanacademy.org/science/biology/human-biology/neuron-nervous-system/a/overview-of-neuron-structure-and-function

There are four main types of glial cells in the adult vertebrate nervous system. Three of these, astrocytes, oligodendrocytes, and microglia, are found only in the central nervous system (CNS). The fourth, the Schwann cells, are found only in the peripheral nervous system (PNS).

Every type of neuron has a non-functional Soma, the cell body that maintains the cell and keeps it running. It also has four functional parts:

https://www.quora.com/What-are-the-parts-of-the-neuron-and-their-function

An input component: This is where signals come in, the duration and strength of the response is equal to the duration and length of the incoming signal. These are the dendrites.

An activation/summation component: here all signals are collected and action potentials are created. This is the Axon Hillock, the thicker part that connects the axon to the soma.

Action potentials only initiate when a certain threshold is reached, after that any change in the incoming signal strength leads to a greater frequency of the action potential. So stronger incoming signal means faster outgoing rhythm.

Duration of the incoming signal determines the amount of action potentials.

Strength and duration of the incoming signal thus creates a sort of code. At the start you might have a strong incoming signal that fades, the outgoing signal is composed of many action potentials in quick succession tapering down to few spread apart.

A long distance communication component: Action Potentials are all-or-none and every one will be sent over the entire axon with the same strength (no such thing as a small or large action potential). The information is coded into the frequency and total number of action potentials. This is done by the axon, and some neurons have myelinated axons which increase the speed.

An output component: At the end of the neuron the action potential is translated from an electric into a chemical signal. The action potential determines the amount of neurotransmitter that is released. These are the axon terminal buttons and synapses and connect to the dendrites of other neurons.

http://www.chegg.com/homework-help/questions-and-answers/list-4-major-parts-neuron-describe-conduction-action-potential-axon-include-depolarization-q19163172

List the 4 major parts of the neuron. Describe the conduction of the action potential down the axon. Include depolarization to threshold, the opening and closing of sodium and potassium channels, the nodes of ranvier, myelin sheaths, and saltatory conduction. Describe the cascade of events within the terminal button which lead to the release of neurotransmitter. You will want to talk about calcium ions, synaptic vesicles, and exocytosis.

 

Expert Answer

Answer- Neurones is a nerve cell that carries electric impulse.It is a basic unit of nervous system and the most important part of brain. Each neuron contain four major part. Cell body Nucleus Axon And dendrites. Cell body contain nucleus inside whic... view the full answer

FOUR PARTS NEURON

 

https://www.ncbi.nlm.nih.gov/books/NBK21535/

Although the morphology of various types of neurons differs in some respects, they all contain four distinct regions with differing functions: the cell body, the dendrites, the axon, and the axon terminals (Figure 21-1).

DUODENUM FOUR PARTS

https://en.wikipedia.org/wiki/Gastrointestinal_tract

Upon dissection, the duodenum may appear to be a unified organ, but it is divided into four segments based upon function, location, and internal anatomy. The four segments of the duodenum are as follows (starting at the stomach, and moving toward the jejunum): bulb, descending, horizontal, and ascending. The suspensory muscle attaches the superior border of the ascending duodenum to the diaphragm.

 

The gastrointestinal tract has a form of general histology with some differences that reflect the specialization in functional anatomy.[18] The GI tract can be divided into four concentric layers in the following order:

 

Mucosa

Submucosa

Muscular layer

Adventitia or serosa

Drugs that contain four rings not fused together but are sometimes classified as TeCAs include:

https://en.wikipedia.org/wiki/Tetracyclic_antidepressant

Marketed

Amoxapine (Asendin) — often classified as a secondary amine tricyclic antidepressant

Loxapine (Loxapac, Loxitane, Adasuve) — a tricyclic antipsychotic with antidepressant properties; produces amoxapine as an active metabolite

Mazindol (Mazanor, Sanorex)

Never marketed

Ciclazindol (WY-23,409)

FOURTH DENISOVAN FOSSIL

 

The tooth is potentially the oldest of the four Denisovan specimens found at the cave (pictured), having been found in a geological layer formed between 227,000 and 128,000 years ago

 

 

Read more: http://www.dailymail.co.uk/sciencetech/article-4682094/Scientists-discover-fourth-Denisovan-fossil.html#ixzz4pURcNw4k

Follow us: @MailOnline on Twitter | DailyMail on Facebook

 

But it is potentially the oldest of the four Denisovan specimens found at the cave, having been found in a geological layer formed between 227,000 and 128,000 years ago.

 

 

Read more: http://www.dailymail.co.uk/sciencetech/article-4682094/Scientists-discover-fourth-Denisovan-fossil.html#ixzz4pURpgVsi

Follow us: @MailOnline on Twitter | DailyMail on Facebook

 

It is potentially the oldest of the four Denisovan specimens found at the cave, having been found in a geological layer formed between 227,000 and 128,000 years ago.

 

 

Read more: http://www.dailymail.co.uk/sciencetech/article-4682094/Scientists-discover-fourth-Denisovan-fossil.html#ixzz4pURsIp5D

Follow us: @MailOnline on Twitter | DailyMail on Facebook

FOUR DENISOVAN FOSSILS

http://www.iflscience.com/plants-and-animals/this-tooth-once-belonged-to-a-member-of-a-mysterious-species-of-humans-that-we-know-almost-nothing-about/

A molar from Denisova Cave, Siberia, comes from the mysterious people to which the cave gives its name, increasing the number of Denisovan fossils to just four. Moreover, while the other fossils are of similar ages, this one is substantially older. Given their role in our evolution, the tooth is one of the most precious artifacts known to science.

PHANEROZOIC FOUR SPECIES

 

http://www.web-expressions.ca/gira/?tag=first-day

Within the upper portion of the Proterozoic sediments, scientists have found the first evidence of animal life. A distinct species of a jelly fish, a sponge, traces of worm burrowing and traces of shelly fragments that may relate to a fourth species have been found. This is indicative of the first created animal life on Earth. See Figure A-4. These 4 species would represent the first appearance of 4 new animal phyla.

FOUR MAJOR EVENTS

https://en.wikiversity.org/wiki/Phanerozoic/Silurian_period

The Silurian period is divided into four major events that occurred during that time.

 

Llandoverian[edit]

The Llandoverian Epoch lasted between 446 to 428 million years ago.

 

Three paleocontinents suggests that at least four global highstands occurred during this epoch. The fluctuation between these events averaged between 2.5 million years apart from each other. Between the Llandovery and Wedlock boundries marks the Irreviken event[4] During the event was a change in carbon and oxygen isotope levels that sparked a mass extinction event.

 

Wenlockian[edit]

The Wenlockian Epoch lasted between 428 to 422 million years ago.

 

 

One of the biggest sea level rises occured in this epoch. Also retains a secundo-episode (warmer sea waters and CO2 level rise) that caused a mass extinction

 

Landlovian[edit]

The Landlovian Epoch lasted between 422 to 418 million years ago. Known for the Lau event. The Lau Event declares the date for a mass extinction event of conodont fauna due to a low point in sea level

 

Also known as the Ludlow epoch, known for a lowstand in sea level. This event caused a mass extinction for conodont fauna.

 

Pridolian[edit]

The Pridolian Epoch lasted between 418 to 417 million years ago.

FOUR CYCLES

https://www.ck12.org/book/CK-12-Earth-Science-Concepts-For-Middle-School/section/11.24/

Since then Earth’s climate has gone through four cycles of frigid glaciers and warm tropical seas. Some organisms survive changes in the climate. Others go extinct when the climate changes too much.

Phanerozoic

Four gastric pouches

http://www.tulane.edu/~bfleury/diversity/labguide/spngnem.html

Examine slides of the Aurelia Ephyra, an early stage in the jellyfish life cycle. Look for the mouth and the tentacles. Can you see the four gastric pouches which extend from the mouth and stomach? The horseshoe shapes inside the gastric pouches are the gonads. A complex system of canals connects these pouches with a ring canal that runs along the outer edge of the umbrella. Food and seawater are circulated throughout the umbrella.

FOUR SEGMENTS

http://www.meddean.luc.edu/lumen/meded/neuro/neurovasc/navigation/ica.htm

Four segments: cervical, petrous, cavernous, and supraclinoid

However, according to Khaldei himself, when he arrived at the Reichstag, he simply asked the soldiers who happened to be passing by to help with the staging of the photoshoot;[13][14] there were only four of them, including Khaldei, on the roof:[15] the one who was attaching the flag was 18-year-old Private Alexei Kovalyov from Kiev, the two others were Abdulkhakim Ismailov from Dagestan and Leonid Gorychev (also mentioned as Aleksei Goryachev) from Minsk.[14][15][16]

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