Jaune d'œufthumb|upright=1.6|Coupe (vue de dessus, pour un oeuf dont le grand axe est horizontal) d’un œuf de poule domestique : le jaune, au centre, est entouré par le blanc. 1. Coquille calcaire 2. Membrane coquillière externe 3. Membrane coquillière interne 4. Chalaze 5. Blanc d’œuf (ou albumen) externe (fluide) 6. Blanc d’œuf (ou albumen) intermédiaire (visqueux) 7. Peau du jaune d’œuf (ou vitellus) 8. Jaune d’œuf (l'ovule) formé 9. Point blanc puis embryon 10. Jaune d’œuf (ou vitellus) jaune 11.
Gouttière neuralevignette|Schéma de la formation de la crête neurale à partir de la plaque neurale. La gouttière neurale est le sillon qui se forme par invagination de la plaque neurale au cours de la neurulation de l'embryon chez les Chordés. Cette invagination soulève les bords de la plaque neurale qui s'épaississent en bourrelets neuraux : ces deux bords du neuroectoderme se rapprochent et s'unissent ensuite jusqu'à former le tube neural. Elle correspond à l'étape intermédiaire de la neurulation qui comporte 3 stades : plaque neurale, gouttière neurale et tube neural.
BlastodermA blastoderm (germinal disc, blastodisc) is a single layer of embryonic epithelial tissue that makes up the blastula. It encloses the fluid filled blastocoel. Gastrulation follows blastoderm formation, where the tips of the blastoderm begins the formation of the ectoderm, mesoderm, and endoderm. The blastoderm is formed when the oocyte plasma membrane begins cleaving by invagination, creating multiple cells that arrange themselves into an outer sleeve to the blastocoel.
SomitomereIn the developing vertebrate embryo, the somitomeres (or somatomeres) are collections of cells that are derived from the loose masses of paraxial mesoderm that are found alongside the developing neural tube. In human embryogenesis they appear towards the end of the third gestational week. The approximately 50 pairs of somitomeres in the human embryo, begin developing in the cranial (head) region, continuing in a caudal (tail) direction until the end of week four.
SchizocœliePar opposition à l'entérocœlie, la schizocœlie caractérise la formation du cœlome à partir d'une fente du mésoderme. Ce type de formation embryonnaire est caractéristique des trochozoaires. La schizocœlie un type de formation du cœlome caractéristique des métazoaires tridermiques cœlomates protostomiens (en opposition à deutérostomiens pour qui le cœlome se forme selon une entérocœlie, une évagination de la paroi de l'archentéron qui est l'intestin primitif présent chez les embryons). Cœlome Protostomia En
Embryological origins of the mouth and anusThe embryological origin of the mouth and anus is an important characteristic, and forms the morphological basis for separating bilaterian animals into two natural groupings: the protostomes and deuterostomes. In animals at least as complex as an earthworm, a dent forms in one side of the early, spheroidal embryo. This dent, the blastopore, deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus, while the gut eventually tunnels through the embryo until it reaches the other side, forming an opening that becomes the mouth.
Cell polarityCell polarity refers to spatial differences in shape, structure, and function within a cell. Almost all cell types exhibit some form of polarity, which enables them to carry out specialized functions. Classical examples of polarized cells are described below, including epithelial cells with apical-basal polarity, neurons in which signals propagate in one direction from dendrites to axons, and migrating cells. Furthermore, cell polarity is important during many types of asymmetric cell division to set up functional asymmetries between daughter cells.
Intermediate mesodermIntermediate mesoderm or intermediate mesenchyme is a narrow section of the mesoderm (one of the three primary germ layers) located between the paraxial mesoderm and the lateral plate of the developing embryo. The intermediate mesoderm develops into vital parts of the urogenital system (kidneys, gonads and respective tracts). Factors regulating the formation of the intermediate mesoderm are not fully understood.
Brain vesicleBrain vesicles are the bulge-like features of the early development of the neural tube in vertebrates. Vesicle formation begins shortly after anterior neural tube closure at about embryonic day 9.0 in the mouse and the fourth and fifth gestational week in human development. In zebrafish and chicken embryos, brain vesicles form by about 24 hours and 48 hours post-conception, respectively. Initially there are three primary brain vesicles: prosencephalon, mesencephalon, and rhombencephalon.
MyogenèseLa myogenèse (du grec myo « muscle » et genesis « naissance ») est un phénomène biologique qui conduit à la formation des tissus musculaires. Elle a d'abord lieu lors du développement de l'embryon, puis lors de certains phénomènes de réparation (après un dommage musculaire par exemple). La myogenèse fait intervenir des facteurs de croissance : FGF (Fibroblast Growth Factor) et TGF (Transforming Growth Factor), des facteurs de transcription spécifiques du muscle (MRF, myogenic regulatory factor) les facteurs MEF (Myocyte Enhance Factor).
