Regression of primitive streak, Biology

Regression of Primitive Streak

As the inward migration of cells by the primitive streak ends progressively along its anterior to posterior regions the streak slowly regresses in the same direction. As the streak shortens the Hensen's Node that forms its anterior end, also moves in a posterior direction at the same time, the presumptive notochordal cells still remaining in the epiblast migrate inward through the posteriorly moving node adding to the length of the notochord. So the regressing streak leaves behind in its path the dorsal axis of the embryo represented by the posteriorly lengthening notochord. By the time the streak disappears and the Hensen's Node arrives at the last position at the posterior border of area pellucida all the presumptive endodermal and mesodermal cells have left the epiblast that now contains only the ectodermal cells. Regression of streak starts after about 22 hours of incubation and is completed in the next about 20 hours. It should be noted that not like amphibian gastrulation differentiation of axial structures and some organs like neural tube, somites, foregut, heart, takes place cephalocaudally along with the progress of later stages of gastrulation in chick embryos.

 

Posted Date: 1/25/2013 5:57:51 AM | Location : United States







Related Discussions:- Regression of primitive streak, Assignment Help, Ask Question on Regression of primitive streak, Get Answer, Expert's Help, Regression of primitive streak Discussions

Write discussion on Regression of primitive streak
Your posts are moderated
Related Questions
Define Field Test used to Assess Aerobic Capacity? A field test that has been used extensively in nutrition studies to assess aerobic capacity measures Heart Rate responses to

Define Importance of Nutrient and Drug Interaction? Certain foods, beverages, alcohol, caffeine, and even cigarettes can interact with medicines. This may make them less effect

Define Muscular endurance component for physical fitness? It is the ability of a muscle, or a group of muscles to sustain repeated contractions or to continue applying force ag

Some foods are better able to resist changes in pH than others. These tend to resist changes in pH since these are buffered and the ability to resist changes in pH is known as bu

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Define Sweetness as a Function of Sugar? Sweetness is the most recognized functional property of sweeteners. Our preference for sweetness, regarded as innate, is apparent soon

Define Precautions for Estimation of Vitamin c in Chillies? 1. Rinse all glassware with 3% metaphosphoric acid before you begin your practical and subsequently each time you wa

Enteral Nutrition  (EN) By definition, the term  enteral  means  "within or by the way of  the gastrointestinal (GI) tract." As described above, enteral is defined as provision

Reversion flavor:  The rapid oxidation of branched furan fatty acids on exposure to light, leads to the production of an intensive aromatic substance, which along with diacety

The goals of biological classification The world of animal diversity is quite complex and it requires an ability to recognise similarities and differences among organisms. Class