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Érythrocyte [show article only]
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Cellule sanguine
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Érythrocytes. L’érythrocyte (du grec erythros : rouge et kutos : cellule), aussi appelée hématie, ou plus communément globule rouge, fait partie des éléments figurés du sang. Chez les mammifères, c'est une cellule anucléée (dépourvue de noyau), tandis que chez les oiseaux c'est une cellule nucléée. Son cytoplasme est riche en hémoglobine, qui assure le transport du dioxygène (O2), mais très pauvre en organites qui n'existent qu'à l'état de
1. Red and white human blood cells as seen under a microscope using a blue slide stain 2. Diagram showing the development of different blood cells from haematopoietic stem cells to mature cells. 3. Scanning electron microscope image of circulating human blood, showing red and white blood cells (a few lymphocytes, monocytes, neutrophils), and disc-shaped platelets Sang
trace. Le terme d'anémie s'applique parfois (dans le langage courant en particulier) à une diminution du nombre de globules rouges, mais en réalité elle est définie par une diminution du taux d'hémoglobine (les deux étant souvent simultanées). Le volume relatif des globules rouges ou hématocrite est le volume occupé par les hématies dans un volume donné du sang total.
Sommaire
1. Human blood smear: a – erythrocytes; b – neutrophil; c – eosinophil; d – lymphocyte. 2. A scanning electron microscope (SEM) image of a normal red blood cell, a platelet, and a white blood cell. 3. Two tubes of EDTA -anticoagulated blood. Left tube: after standing, the RBCs have settled at the bottom of the tube. Right tube: contains freshly drawn blood. 4. Vertebrate red blood cell types, measurements in micrometers
1 Aspect d'un globule rouge mammalien normal 2 Physiologie 3 Valeurs plasmatiques normales 4 La moelle osseuse 5 Composition 6 Rôle des hématies 7 Anomalie 8 Bibliographie 9 Notes et références
Mammifère
Aspect d'un globule rouge mammalien normal
1. Goat kids will stay with their mother until they are weaned.
Un érythrocyte normal se présente de profil comme un disque biconcave, de face comme un disque à centre plus clair : c'est une sorte de poche contenant l'hémoglobine. Cette forme lui confère une élasticité importante, qui permet le transport de dioxygène à travers certains capillaires étroits. Le diamètre normal des globules rouges de face varie de 6,7 à 7,7 micromètres (moyenne 7,2 micromètres). Ils sont en forme de disques biconcaves (région centrale : 0,8 micromètres, région périphérique : 2,6 micromètres) la plus apte à une fixation maximale. Vus au microscope optique à l'état frais, ils sont de couleur rouge-orangé ; sur un frottis mince coloré au May-Grünwald Giemsa ou à la coloration de Wright, ils apparaissent plus rose. Leur forme est très bien visualisée au microscope électronique à balayage (MEB). Sur frottis épais, les globules rouges se disposent volontiers en rouleaux (particulièrement en présence d'un excès de fibrinogène ou d'une paraprotéine) et sont alors vus de profil.
Physiologie La biosynthèse des globules rouges commence au stade embryonnaire, à partir de la 3e semaine de développement, au niveau du sac vitellin. La synthèse d'érythrocytes par le sac vitellin diminue vers la 5e semaine pour disparaître complètement lors de la 9e semaine de développement. Le relai est pris au cours du 3e mois par le foie, puis par la moelle osseuse hématopoïétique à partir du 5e mois de développement[1]. Cette dernière restera le seul site de synthèse des érythrocytes chez l'adulte. Chez l'adulte, les globules rouges sont élaborés dans la moelle osseuse dite moelle hématopoïétique, que l’on retrouve dans les os plats (côtes, sternum, calvaria, os coxaux, clavicules) et aux extrémités (épiphyses) des os longs. La fabrication d'hématies par la moelle osseuse est appelée érythropoïèse. Tout commence avec des cellules souches hématopoïétiques, qui sont dites pluripotentes (elles pourront donner naissance à plusieurs types cellulaires). Certaines vont ensuite commencer à se différencier, et vont former les progéniteurs (BFU-E, CFU-E). Les premières cellules de la lignée érythrocytaire morphologiquement identifiables sont appelées proérythroblastes (pronormoblastes). Par division cellulaire (mitose) on passe à l'érythroblaste (normoblaste) basophile (en référence à la coloration du cytoplasme après coloration de May-Grünwald-Giemsa), puis à l'érythroblaste (normoblaste) polychromatophile de type I, puis de type II (également appelé orthochromatique, car la couleur de son cytoplasme est quasi-identique à celle de l'hématie) ; toutes ces cellules sont nucléées et -sauf circonstances pathologiques- sont exclusivement médullaires. À chaque étape, on observe une diminution de taille de la cellule (et de son noyau). Au fur et à mesure, les cellules vont se charger en hémoglobine, responsable de la couleur rouge de leur cytoplasme, et la concentration cytoplasmique en hémoglobine augmente. À la fin (« à l'entrée dans la circulation », pourrait-on dire), l'érythroblaste perd son noyau. Quelques mitochondries et des fragments de REG (réticulum endoplasmique granuleux) ou de Golgi persistent : c'est un réticulocyte qui a l'apparence d'un globule rouge en microscopie optique (une coloration spécifique est nécessaire pour le mettre en évidence, au bleu de crésyl brillant ou par fluorescence). Après quoi, l’expulsion de ces derniers résidus donnera naissance au globule rouge (érythrocyte ou hématie) mûr. L'érythropoïèse est régulée par différents facteurs de croissance. L'érythropoïétine (EPO) va agir en stimulant les progéniteurs, surtout les CFU-E, et ainsi favoriser in fine la production de globule rouge. L'érythropoïétine est majoritairement produite par le cortex rénal (environ 90 % de la production) mais peut aussi être produite par le foie, le cerveau, l'utérus et peut même être produite artificiellement. Elle est actuellement utilisée à titre thérapeutique pour stimuler la production de globules rouges dans le traitement de certaines anémies, insuffisance rénale, au cours de certains traitements aplasiants… et comme agent dopant chez certains athlètes.
Noyau (biologie)
1. HeLa cells stained for nuclear DNA with the Blue Hoechst dye. The central and rightmost cell are in interphase, thus their entire nuclei are labeled. On the left, a cell is going through mitosis and its DNA has condensed. 2. Oldest known depiction of cells and their nuclei by Antonie van Leeuwenhoek, 1719 3. Drawing of a Chironomus salivary gland cell published by Walther Flemming in 1882. The nucleus contains Polytene chromosomes. 4. A mouse fibroblast nucleus in which DNA is stained blue. The distinct chromosome territories of chromosome 2 (red) and chromosome 9 (green) are stained with fluorescent in situ hybridization. Oiseau
1. Archaeopteryx lithographica is often considered the oldest known true bird. 2. Confuciusornis sanctus, a Cretaceous bird from China 3. The range of the house sparrow has expanded dramatically due to human activities. Cytoplasme
1. Proteins in different cellular compartments and structures tagged with green fluorescent protein 2. Nucleolus Organite
1. (A) Electron micrograph of Halothiobacillus neapolitanus cells, arrows highlight carboxysomes. (B) Image of intact carboxysomes isolated from H. neapolitanus. Scale bars are 100 nm. 2. Nucleolus Fibrinogène
Chez l'homme, leur durée de vie atteint 120 jours, et près de 1 % des globules rouges d'un individu sont remplacés quotidiennement[2].
Valeurs plasmatiques normales Diamètre : 7 µm. Hématocrite : 47 % chez l'homme (±7 %) ; 42 % chez la femme (±5 %). Nombre moyen de globules rouges : 4,6 à 6,2 T/L chez l'homme et de 4,2 à 5,4 T/L chez la femme. Taux globulaire moyen d'hémoglobine (TGMH = Hémoglobine par Globule rouge) : de 28 à 34 pg.
La moelle osseuse La moelle osseuse assure le renouvellement des cellules du sang. Globules rouges, globules blancs et plaquettes sont produits au cœur des os. La moelle osseuse se retrouve à l`intérieur de l`os, c'est elle qui produit les cellules souches (hématopoïèse). Qui sont à l`origine de la production des cellules sanguines.
1. crystal structure of native chicken fibrinogen with two different bound ligands Hématopoïèse
1. Diagram showing the development of different blood cells from haematopoietic stem cell to mature cells Os coxal
Composition
On trouve environ 30 pg d'hémoglobine par hématie. Ce sont des disques aplatis, avec un centre plus fin que les bords. Leur forme est dite biconcave. La membrane érythrocytaire, est constituée d'une bi-couche lipidique dont la partie centrale entre les surfaces, externe et interne, est hydrophobe. Divers glycolipides et protéines plus ou moins glycosylées -dont le polymorphisme est à l'origine des groupes sanguins (ABO, MNS, Rh, Kell, etc. présents à la surface des hématies), glycophorines, aquaporines, AChe, Glut 1, Na+/K+ ATPase et protéine bande 3 (transférant HCO3- contre Cl-), entre autres, traversent ou sont également présents sur cette membrane, offrent une protection mécanique et antiagrégante (glycocalix), ou contre l'action du complément (DAF (en) et CD59), permettent les échanges entre l'érythrocyte et le milieu extérieur ou l'ancrage de cette membrane lipidique au cytosquelette interne. Leur cytosquelette, a été découvert au début des années 1980 et comprend : spectrine (dimère), protéine bande 4.1 (fixant l'actine), ankyrine, glycophorine (dimère), protéine bande 3, et des microfilaments intermédiaires à l'intérieur, leur permettant de conserver leur forme caractéristique, tout en leur conférant une très grande souplesse, indispensable pour passer dans les capillaires sanguins les plus fins. Chez les mammifères, ils n'ont pas de noyau, et par conséquent pas d'ADN nucléaire ni d'ailleurs de mitochondries. En revanche, les actinoptérygiens, les amphibiens et les reptiles (au sens phylogénétique donc incluant les oiseaux) possèdent des hématies nucléées (Sporn and Dingman, 1963, Science).
Rôle des hématies Le transport de l'oxygène des poumons aux tissus et cellules du corps, grâce à l'hémoglobine contenue dans l'ergastoplasme (réticulum endoplasmique granuleux), à l'intérieur des globules rouges. La régulation du pH sanguin et le transport du CO2 grâce à l'anhydrase carbonique,
1. Position of the hip bones (shown in red) 2. Hip bone.Medial view. Érythropoïèse
1. Haematopoiesis Cellule souche
1. Transmission electron micrograph of an adult stem cell displaying typical ultrastructural characteristics. 2. Mouse embryonic stem cells with fluorescent marker 3. Human embryonic stem cell colony on mouse embryonic fibroblast feeder layer Mitose
une enzyme présente à la surface des hématies qui transforme les bicarbonates en CO2 ou l'inverse, selon les besoins du corps. Ainsi, les hématies transforment le
CO2 fabriqué par les cellules en bicarbonates, puis elles vont jusqu'aux poumons,
où elles retransforment le bicarbonate en CO2. Le transport de complexes immuns grâce au CD20, une molécule présente à la surface des hématies, qui fixe les complexes immuns et permet de les déplacer. Mais ceci est une arme à double tranchant, car en cas d'excès de complexes immuns dans le sang (par exemple au cours d'un lupus érythémateux systémique), les hématies déposent des complexes immuns dans le rein, ce qui aggrave les lésions rénales lors des lupus. Chez l'homme, elles portent à leur surface les antigènes des groupes sanguins érythrocytaires ABO, rhésus, Kell, Duffy[2], entre autres.
1. Onion (Allium) cells in different phases of the cell cycle enlarged 800 diameters. a. non-dividing cells b. nuclei preparing for division (spireme-stage) c. dividing cells showing mitotic figures e. pair of daughter-cells shortly after division 2. Mitosis in an animal cell. Réticulocyte
Anomalie
Les hématies peuvent faire l'objet d'anomalies quantitatives : anémie dans un cas, polyglobulie dans l'autre. Les hématies peuvent être malformées à la suite d'une déficience génétique ou beaucoup plus souvent, à une autre cause : Anomalies globales : Acanthocytes Anisochromie Anisocytose Annulocytes Codocytes (Cellule-cible, en anglais : Target cells) Dacryocytose Drépanocytose (Drépanocytes ou « cellules en faucille » ou « cellules en feuille de houx ») Elliptocytes Fragmentocytes ou schizocytes (synonyme) Hypochromie Macrocytose Mégalocytose Microcytose Ovalocytose Poïkilocytose Polychromatophilie Rouleau formation Schistocytes Schizocytes, ou fragmentocytes (synonyme) Sidérocytes Sphérocytose Stomatocytes
Anomalies internes (inclusions dans les globules rouges) : Réticulocyte (caractérise des hématies jeunes dont la proportion dans la circulation est appelée réticulocytose) Corps de Howell-Jolly Anneaux de Cabot Corps de Heinz Ponctuations basophiles Sidérocytes
Bibliographie (en) Yoshikawa, Haruhisa & Rapoport, Samuel (edited by), Cellular and molecular biology of erythrocytes, Baltimore/Tokyo, University Park Press/ University of Tokyo Press, 1974. (en) Sporn MB, Dingman CW. Histone and DNA in isolated nuclei from chicken brain, liver, and erythrocytes. Science. 1963 Apr 19;140:316-8. (fr) Bader-Meunier B, Cynober T, Tchernia G (2001) Maladies de la membrane du globule rouge ; MTP, Volume 4, numéro 3, Mai - Juin 2001 (fr) https://docs.google.com/document/d/1EQLATlecXGdVHE97EJJeL6Wb0JIuqKrBjRzSKlis7I/edit Rapport de recherche de l`école secondaire Renaissance
1. Supravital stain of a smear of human blood from a patient with hemolytic anemia. The reticulocytes are the cells with the dark blue dots and curved linear structures (reticulum) in the cytoplasm. 2. Reticulocytes Érythropoïétine
2. Erythropoietin Cellule (biologie)
1. Onion (Allium) cells in different phases of the cell cycle 2. Structure of an animal cell 3. A fluorescent image of an endothelial cell. Nuclei are stained blue, mitochondria are stained red, and microfilaments are stained green. 4. Human cancer cells with nuclei (specifically the DNA) stained blue. The central and rightmost cell are in interphase, so the entire nuclei are labeled. The cell on the left is going through mitosis and its DNA has condensed. Leucocyte
1. A scanning electron microscope image of normal circulating human blood. In addition to the irregularly shaped leukocytes, both red blood cells and many small disc-shaped platelets are visible. 2. Monocyte 3. Neutrophil engulfing anthrax bacteria Thrombocyte
Notes et références 1. Développement embryonnaire du système hématopoïétique. 2.
a et b Harrisson, Principes de Médecine Interne (ISBN 2-257-17549-2).
Sang
v · m
Plasma Érythrocytes Leucocytes Granulocytes Neutrophiles Éosinophiles Basophiles Lymphocytes T B NK Monocytes Thrombocytes Cellules sanguines Hématologie Circulation sanguine
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1. Image from a light microscope (500 ×) from a Giemsa-stained peripheral blood smear showing platelets (blue dots) surrounded by red blood cells (pink and circular) 2. Platelets derive from totipotent marrow stem cells 3. Platelets extruded from megakaryocytes 4. Scanning electron micrograph of blood cells. From left to right: human erythrocyte, activated platelet, leukocyte.
1. Cellule sanguine – A blood cell, also called a haematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood. Red blood cells – Erythrocytes White blood cells – Leukocytes Platelets – Thrombocytes, together, these three kinds of blood cells add up to a total 45% of the blood tissue by volume, with the remaining 55% of the volume composed of plasma, the liquid component of blood. The volume percentage of red cells in the blood is measured by centrifuge or flow cytometry and is 45% of cells to total volume in males. Haemoglobin is an protein that facilitates transportation of oxygen from the lungs to tissues. Red blood cells or erythrocytes, primarily oxygen and collect carbon dioxide through the use of haemoglobin. In the process of being formed they go through a unipotent stem cell stage and they have the job alongside the white blood cells of protecting the healthy cells. RBCs are formed in the red marrow in the adults. After the completion of their lifespan, they are destroyed in the spleen, White blood cells or leukocytes, are cells of the immune system involved in defending the body against both infectious disease and foreign materials. Five diverse types of leukocytes exist, and are all produced and derived from multipotent cells in the bone known as a hematopoietic stem cells. They live for about 3 to 4 days in the human body. Leukocytes are found throughout the body, including the blood and lymphatic system, the two main categories of white blood cells are granulocytes and agranulocytes. Neutrophils are the most abundant of all the WBCs, Platelets, or thrombocytes or yellow blood cells, are very small, irregularly shaped clear cell fragments, 2–3 µm in diameter, which derive from fragmentation of precursor megakaryocytes. The average lifespan of a platelet is normally just 5 to 9 days, Platelets are a natural source of growth factors. They circulate in the blood of mammals and are involved in hemostasis, Platelets release thread-like fibers to form these clots. If the number of platelets is too low, excessive bleeding can occur, an abnormality or disease of the platelets is called a thrombocytopathy, which can be either a low number of platelets, a decrease in function of platelets, or an increase in the number of platelets. Platelets release a multitude of factors including Platelet-derived growth factor, a potent chemotactic agent, and TGF beta. Both of these factors have been shown to play a significant role in the repair. Local application of factors in increased concentrations through Platelet-rich plasma has been used as an adjunct to wound healing for several decades 2. Sang – Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma, plasma, which constitutes 55% of blood fluid, is mostly water, and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide, and blood cells themselves. Albumin is the protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are red blood cells, white blood cells. The most abundant cells in blood are red blood cells. These contain hemoglobin, a protein, which facilitates oxygen transport by reversibly binding to this respiratory gas. In contrast, carbon dioxide is mostly transported extracellularly as bicarbonate ion transported in plasma, vertebrate blood is bright red when its hemoglobin is oxygenated and dark red when it is deoxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this blood does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their system to suffice for supplying oxygen. Jawed vertebrates have an immune system, based largely on white blood cells. White blood cells help to resist infections and parasites, platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system, Blood is circulated around the body through blood vessels by the pumping action of the heart. Medical terms related to blood often begin with hemo- or hemato- from the Greek word µ for blood. In terms of anatomy and histology, blood is considered a form of connective tissue, given its origin in the bones. The average adult has a volume of roughly 5 litres. These blood cells consist of erythrocytes, leukocytes, and thrombocytes, by volume, the red blood cells constitute about 45% of whole blood, the plasma about 54. 3%, and white cells about 0. 7%. Whole blood exhibits non-Newtonian fluid dynamics, if all human hemoglobin were free in the plasma rather than being contained in RBCs, the circulatory fluid would be too viscous for the cardiovascular system to function effectively. One microliter of blood contains,4.7 to 6.1 million,4.2 to 5.4 million erythrocytes, Red blood cells contain the bloods hemoglobin, mature red blood cells lack a nucleus and organelles in mammals 3. Mammifère – Mammals are any vertebrates within the class Mammalia, a clade of endothermic amniotes distinguished from reptiles by the possession of a neocortex, hair, three middle ear bones and mammary glands. All female mammals nurse their young with milk, secreted from the mammary glands, Mammals include the largest animals on the planet, the great whales. The basic body type is a quadruped, but some mammals are adapted for life at sea, in the air, in trees. The largest group of mammals, the placentals, have a placenta, Mammals range in size from the 30–40 mm bumblebee bat to the 30-meter blue whale. With the exception of the five species of monotreme, all modern mammals give birth to live young, most mammals, including the six most species-rich orders, belong to the placental group. The largest orders are the rodents, bats and Soricomorpha, the next three biggest orders, depending on the biological classification scheme used, are the Primates, the Cetartiodactyla, and the Carnivora. Living mammals are divided into the Yinotheria and Theriiformes There are around 5450 species of mammal, in some classifications, extant mammals are divided into two subclasses, the Prototheria, that is, the order Monotremata, and the Theria, or the infraclasses Metatheria and Eutheria. The marsupials constitute the group of the Metatheria, and include all living metatherians as well as many extinct ones. Much of the changes reflect the advances of cladistic analysis and molecular genetics, findings from molecular genetics, for example, have prompted adopting new groups, such as the Afrotheria, and abandoning traditional groups, such as the Insectivora. The mammals represent the only living Synapsida, which together with the Sauropsida form the Amniota clade, the early synapsid mammalian ancestors were sphenacodont pelycosaurs, a group that produced the non-mammalian Dimetrodon. At the end of the Carboniferous period, this group diverged from the line that led to todays reptiles. Some mammals are intelligent, with some possessing large brains, self-awareness, Mammals can communicate and vocalize in several different ways, including the production of ultrasound, scent-marking, alarm signals, singing, and echolocation. Mammals can organize themselves into fission-fusion societies, harems, and hierarchies, most mammals are polygynous, but some can be monogamous or polyandrous. They provided, and continue to provide, power for transport and agriculture, as well as commodities such as meat, dairy products, wool. Mammals are hunted or raced for sport, and are used as model organisms in science, Mammals have been depicted in art since Palaeolithic times, and appear in literature, film, mythology, and religion. Defaunation of mammals is primarily driven by anthropogenic factors, such as poaching and habitat destruction, Mammal classification has been through several iterations since Carl Linnaeus initially defined the class. No classification system is accepted, McKenna & Bell and Wilson & Reader provide useful recent compendiums. Though field work gradually made Simpsons classification outdated, it remains the closest thing to a classification of mammals 4. Noyau (biologie) – In cell biology, the nucleus is a membrane-enclosed organelle found in eukaryotic cells. Eukaryotes usually have a nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei. Cell nuclei contain most of the genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones. The genes within these chromosomes are the nuclear genome and are structured in such a way to promote cell function. The nucleus maintains the integrity of genes and controls the activities of the cell by regulating gene expression—the nucleus is, therefore, because the nuclear membrane is impermeable to large molecules, nuclear pores are required to regulate nuclear transport of molecules across the envelope. The pores cross both nuclear membranes, providing a channel through which larger molecules must be transported by carrier proteins while allowing free movement of small molecules. Movement of large molecules such as proteins and RNA through the pores is required for gene expression and the maintenance of chromosomes. The best-known of these is the nucleolus, which is involved in the assembly of ribosomes. After being produced in the nucleolus, ribosomes are exported to the cytoplasm where they translate mRNA, the nucleus was the first organelle to be discovered. What is most likely the oldest preserved drawing dates back to the early microscopist Antonie van Leeuwenhoek and he observed a lumen, the nucleus, in the red blood cells of salmon. Unlike mammalian red blood cells, those of other vertebrates still contain nuclei, the nucleus was also described by Franz Bauer in 1804 and in more detail in 1831 by Scottish botanist Robert Brown in a talk at the Linnean Society of London. Brown was studying orchids under microscope when he observed an opaque area and he did not suggest a potential function. In 1838, Matthias Schleiden proposed that the plays a role in generating cells. He believed that he had observed new cells assembling around cytoblasts, Franz Meyen was a strong opponent of this view, having already described cells multiplying by division and believing that many cells would have no nuclei. The function of the nucleus remained unclear, between 1877 and 1878, Oscar Hertwig published several studies on the fertilization of sea urchin eggs, showing that the nucleus of the sperm enters the oocyte and fuses with its nucleus. This was the first time it was suggested that an individual develops from a nucleated cell, therefore, the necessity of the sperm nucleus for fertilization was discussed for quite some time. However, Hertwig confirmed his observation in other groups, including amphibians. Eduard Strasburger produced the results for plants in 1884 5. Oiseau – Birds live worldwide and range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the class of tetrapods with the most living species, at ten thousand. As a subgroup of Reptilia, birds are the closest living relatives of crocodilians, while birds, the fossil record indicates that birds are also the last surviving representatives of dinosauria, having evolved from feathered ancestors within the theropod group of saurischian dinosaurs. True birds first appeared during the Cretaceous period, around 100 million years ago, dNA-based evidence finds that birds diversified dramatically around the time of the Cretaceous–Palaeogene extinction event which killed off all other dinosaur lineages. Birds, especially those in the continents, survived this event. Primitive bird-like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid-Jurassic period. Birds have wings which are more or less developed depending on the species, the digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have evolved for swimming. Many species annually migrate great distances, Birds are social, communicating with visual signals, calls, and bird songs, and participating in such social behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of species are socially monogamous, usually for one breeding season at a time, sometimes for years. Other species have breeding systems that are polygynous or, rarely, Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents, most birds have an extended period of parental care after hatching. Some birds, such as hens, lay eggs even when not fertilised, songbirds, parrots, and other species are popular as pets. Guano is harvested for use as a fertiliser, Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them. Recreational birdwatching is an important part of the ecotourism industry, the first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use, Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda, Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria 6. Cytoplasme – In cell biology, the cytoplasm is the material within a living cell, excluding the cell nucleus. It comprises cytosol and the organelles – the cells internal sub-structures, all of the contents of the cells of prokaryotic organisms are contained within the cytoplasm. Within the cells of organisms the contents of the cell nucleus are separated from the cytoplasm. The cytoplasm is about 80% water and usually colorless, the submicroscopic ground cell substance or cytoplasmatic matrix which remains after exclusion the cell organelles and particles is groundplasm. It is within the cytoplasm that most cellular activities occur, such as many metabolic pathways including glycolysis, the concentrated inner area is called the endoplasm and the outer layer is called the cell cortex or the ectoplasm. Movement of calcium ions in and out of the cytoplasm is an activity for metabolic processes. In plants, movement of the cytoplasm around vacuoles is known as cytoplasmic streaming, the term was introduced by Rudolf von Kölliker in 1863, originally as a synonym for protoplasm, but later it has come to mean the cell substance and organelles outside the nucleus. There has been disagreement on the definition of cytoplasm, as some authors prefer to exclude from it some organelles. The physical properties of the cytoplasm have been contested in recent years and it remains uncertain how the varied components of the cytoplasm interact to allow movement of particles and organelles while maintaining the cell’s structure. The flow of cytoplasmic components plays an important role in cellular functions which are dependent on the permeability of the cytoplasm. An example of function is cell signalling, a process which is dependent on the manner in which signaling molecules are allowed to diffuse across the cell. While small signaling molecules like calcium ions are able to diffuse with ease, larger molecules, the irregular dynamics of such particles have given rise to various theories on the nature of the cytoplasm. There has long been evidence that the cytoplasm behaves like a sol-gel and it is thought that the component molecules and structures of the cytoplasm behave at times like a disordered colloidal solution and at other times like an integrated network, forming a solid mass. Recently it has proposed that the cytoplasm behaves like a glassforming liquid approaching the glass transition. A cells ability to vitrify in the absence of activity, as in dormant periods. There has been examining the motion of cytoplasmic particles independent of the nature of the cytoplasm. In such an approach, the aggregate random forces within the cell caused by motor proteins explain the nonBrownian motion of cytoplasmic constituents. The three major elements of the cytoplasm are the cytosol, organelles and inclusions, the cytosol is the portion of the cytoplasm not contained within membrane-bound organelles 7. Organite – In cell biology, an organelle is a specialized subunit within a cell that has a specific function. Individual organelles are usually enclosed within their own lipid bilayers. The name organelle comes from the idea that these structures are to cells what an organ is to the body, organelles are identified by microscopy, and can also be purified by cell fractionation. There are many types of organelles, particularly in eukaryotic cells, while prokaryotes do not possess organelles per se, some do contain protein-based bacterial microcompartments, which are thought to act as primitive organelles. In biology organs are defined as confined functional units within an organism, the analogy of bodily organs to microscopic cellular substructures is obvious, as from even early works, authors of respective textbooks rarely elaborate on the distinction between the two. In the 1830s, Félix Dujardin refuted Ehrenberg theory which said that microorganims have the organs of multicellular animals. Credited as the first to use a diminutive of organ for cellular structures was German zoologist Karl August Möbius, under this definition, there would only be two broad classes of organelles, mitochondria plastids. Other organelles are also suggested to have endosymbiotic origins, but do not contain their own DNA, under the more restricted definition of membrane-bound structures, some parts of the cell do not qualify as organelles. Nevertheless, the use of organelle to refer to non-membrane bound structures such as ribosomes is common and this has led some texts to delineate between membranebound and non-membrane bound organelles. The larger organelles, such as the nucleus and vacuoles, are visible with the light microscope. They were among the first biological discoveries made after the invention of the microscope, not all eukaryotic cells have each of the organelles listed below. Exceptional organisms have cells that do not include some organelles that might otherwise be considered universal to eukaryotes, there are also occasional exceptions to the number of membranes surrounding organelles, listed in the tables below. In addition, the number of organelles of each type found in a given cell varies depending upon the function of that cell. This idea is supported in the Endosymbiotic theory, in the past, they were often viewed as having little internal organization, but slowly, details are emerging about prokaryotic internal structures. However, more recent research has revealed that at least some prokaryotes have microcompartments such as carboxysomes and these subcellular compartments are 100–200 nm in diameter and are enclosed by a shell of proteins. The function of a protein is correlated with the organelle in which it resides. CoRR Hypothesis Ejectosome Endosymbiotic theory Organelle biogenesis Membrane vesicle trafficking Host-pathogen interface Tree of Life project, Eukaryotes 8. Fibrinogène – Fibrinogen is a glycoprotein in vertebrates that helps in the formation of blood clots. It consists of an array of three nodules held together by a very thin thread which is estimated to have a diameter between 8 and 15 Angstrom. The two end nodules are alike but the one is slightly smaller. Measurements of shadow lengths indicate that nodule diameters are in the range 50 to 70 Å, the length of the dried molecule is 475 ±25 Å. The fibrinogen molecule is a soluble, large, and complex 340 kDa plasma glycoprotein and it has a rod-like shape with dimensions of 9 ×47.5 ×6 nm and it shows a negative net charge at physiological pH. Fibrinogen is synthesized in the liver by the hepatocytes, the concentration of fibrinogen in the blood plasma is 200–400 mg/dL. During normal blood coagulation, a coagulation cascade activates the zymogen prothrombin by converting it into the serine protease thrombin, thrombin then converts the soluble fibrinogen into insoluble fibrin strands. These strands are then cross-linked by factor XIII to form a blood clot, fXIIIa stabilizes fibrin further by incorporation of the fibrinolysis inhibitors alpha-2-antiplasmin and TAFI, and binding to several adhesive proteins of various cells. Both the activation of factor XIII by thrombin and plasminogen activator are catalyzed by fibrin, research from 2011 has shown that fibrin plays a key role in the inflammatory response and development of rheumatoid arthritis. In its natural form, fibrinogen can form bridges between platelets, by binding to their GpIIb/IIIa surface membrane proteins, however, its function is as the precursor to fibrin. Fibrinogen, the protein of vertebrate blood clotting, is a hexamer. The N-terminal sections of three chains contain the cysteines that participate in the cross-linking of the chains. The C-terminal parts of the , and chains contain a domain of about 225 amino-acid residues, in fibrinogen as well as in angiopoietin, this domain is implicated in protein-protein interactions. In lectins, such as mammalian ficolins and invertebrate tachylectin 5A, on the fibrinogen and chains, there is a small peptide sequence. These small peptides are what prevent fibrinogen from spontaneously forming polymers with itself, the conversion of fibrinogen to fibrin occurs in several steps. First, thrombin cleaves fibrinopeptide A and B located on the N-terminus of the fibrinogen alpha, the resulting fibrin monomers polymerize end to end to from protofibrils, which in turn associate laterally to form fibrin fibers. In a final step, the fibrin fibers associate to form the fibrin gel, congenital fibrinogen deficiency or disturbed function of fibrinogen has been described in a few cases. It can lead to bleeding or thromboembolic complications, or is clinically without pathological findings 9. Hématopoïèse – Haematopoiesis is the formation of blood cellular components. All cellular blood components are derived from stem cells. In a healthy person, approximately 1011–1012 new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation. Haematopoietic stem cells reside in the medulla of the bone and have the ability to give rise to all of the different mature blood cell types and tissues. HSCs are self-renewing cells, when they proliferate, at least some of their daughter cells remain as HSCs, so the pool of stem cells is not depleted. This phenomenon is called asymmetric division. The other daughters of HSCs can follow any of the other pathways that lead to the production of one or more specific types of blood cell. The pool of progenitors is heterogeneous and can be divided into two groups, longterm self-renewing HSC and only transiently self-renewing HSC, also called short-terms and this is one of the main vital processes in the body. All blood cells are divided into three lineages, erythroid cells are the oxygen carrying red blood cells. Both reticulocytes and erythrocytes are functional and are released into the blood, in fact, a reticulocyte count estimates the rate of erythropoiesis. Lymphocytes are the cornerstone of the immune system. They are derived from common lymphoid progenitors, the lymphoid lineage is primarily composed of T-cells and B-cells. In developing embryos, blood formation occurs in aggregates of cells in the yolk sac. As development progresses, blood formation occurs in the spleen, liver, when bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism. However, maturation, activation, and some proliferation of lymphoid cells occurs in the spleen, thymus, in children, haematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it mainly in the pelvis, cranium, vertebrae. In some cases, the liver, thymus, and spleen may resume their haematopoietic function and it may cause these organs to increase in size substantially. During fetal development, since bones and thus the bone marrow develop later, therefore, the liver is enlarged during development. In some vertebrates, haematopoiesis can occur wherever there is a loose stroma of connective tissue and slow blood supply, such as the gut, spleen or kidney 10. Os coxal – The hip bone is a large flat bone, constricted in the center and expanded above and below. In some vertebrates it is composed of three parts, the ilium, ischium, and the pubis, the two hip bones join at the pubic symphysis and together with the sacrum and coccyx comprise the skeletal component of the pelvis – the pelvic girdle which surrounds the pelvic cavity. They are connected to the sacrum, which is part of the axial skeleton, each hip bone is connected to the corresponding femur through the large ball and socket joint of the hip. The hip bone is formed by three parts, ilium, ischium, and pubis, at birth, these three components are separated by hyaline cartilage. They join each other in a Y-shaped portion of cartilage in the acetabulum, by the end of puberty the three regions will have fused together, and by the age of 25 they will have ossified. The two hip bones join each other at the pubic symphysis, together with the sacrum and coccyx, the hip bones form the pelvis. Ilium is the uppermost and largest region and it makes up two fifths of the acetabulum. The body of ilium forms the joint with the sacrum. The edge of the wing of ilium forms the S-shaped iliac crest which is located through the skin. The iliac crest shows clear marks of the attachment of the three abdominal wall muscles, the ischium forms the lower and back part of the hip bone and is located below the ilium and behind the pubis. The ischium is the strongest of the three regions that form the hip bone and it is divisible into three portions, the body, the superior ramus, and the inferior ramus. The body forms approximately one-third of the acetabulum, the ischium forms a large swelling, the tuberosity of the ischium, also referred to colloqially as the sit bone. When sitting, the weight is placed upon the ischial tuberosity. The gluteus maximus covers it in the posture, but leaves it free in the seated position. The pubic region or pubis is the ventral and anterior of the three forming the hip bone. It is divisible into a body, a superior ramus, the body forms one-fifth of the acetabulum. The body forms the wide, strong, medial and flat portion of the bone which unites with the other pubic bone in the pubic symphysis. The fibrocartilaginous pad which lies between the surfaces of the coxal bones, that secures the pubic symphysis, is called the interpubic disc