Gastrulation and laying the down longitudinal body axis.
As a morphogenetic process, gastrulation is crucial as it forms the first embryonic tissues layers x. The primary function of gastrulation is the morphogenetic movement whereby the three layers become establishedx. It is also the first stage where cleaving, budding egg transforms to take some semblance of the prospective embryo. Three days after fertilisation zygote undergoes cell division which results in bulk of cells called morulax which in-turn undergoes transformation where morula interior hollows out; this structure is blastocyst in mammals. In the 2nd week, mesenchymal cells arrange along the prospective midline of the late blastocyst establishing the first embryonic axis , an early structure named primitive streak arises through this midline and enables identification of anterior-posterior body axis; it serves as morphological indication for the initiation of the phenomenon Gastrulationx. This event is significant because it establish the bilateral symmetry, defines anterior-posterior region and initiates germ layer formation. Presumptive epiblast or primitive ectoderm migrates towards the primitive streak forming the endoderm layer by the process invaginationx; the endoderm cells contributesx to the formation of epithelium of Digestive System and Respiratory System, predominantly organs associated with digestive system. The hypoblast is pushed towards exterior which eventually contributes to amnion formation. At HH stage 4x, anterior-posterior length of primitive streak reaches its maximum at which point the mesodermal.. Epiblastx later contributes to the formation of definite ectoblast which forms epidermis, neural crest and Nervous System. The in-between mesodermx layer later give rises to muscles, cartilage, vertebrae, the dermis, notochord, blood and blood vessels, bones and connective tissues. The formation of 3 germ layer when formed are disorganized, the manipulation induced by the...
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