Extra-embryonic membranes and placenta, Biology

Extra-Embryonic Membranes and Placenta

The extra embryonic membranes like you already know provide nourishment and protection. These membranes are fundamentally similar to the extra-embryonic membranes of reptiles and birds, however the method of origin differs in humans. During the third and fourth week, the amnion grows around the embryo enclosing it in a membranous fluid filled sac in which the growing embryo and later the foetus floats and can move freely. This sac as mentioned in the previous section is a shock absorber and encloses a fluid, the amniotic fluid, that helps to keep the temperature of foetal environment stable. Another membrane, the chorion develops from the trophoblast cells. The chorion is a extremely specialised extraembryonic tissue. It facilitates the transfer of gases, nutrients and wastes among the embryo and the mother. It is the primary part of the placenta that we will study a little later. Yolk sac develops during the second week of development even though there is no yolk in the human egg. It does not give nourishment to the embryo but it becomes surrounded by mesoderm that forms the blood cells till the liver of the embryo becomes functional in the sixth week. The yolk sac with the allantois forms the umbilical cord. Part of the yolk sac also forms the lining of the gut. The allantois that forms during the third week of development is a tiny sausage shaped pouch on the yolk sac. It also is accountable for producing blood cells and later develops into the umbilical blood vessels.

Posted Date: 2/1/2013 5:07:40 AM | Location : United States







Related Discussions:- Extra-embryonic membranes and placenta, Assignment Help, Ask Question on Extra-embryonic membranes and placenta, Get Answer, Expert's Help, Extra-embryonic membranes and placenta Discussions

Write discussion on Extra-embryonic membranes and placenta
Your posts are moderated
Related Questions
a) A cat has just arrived to the veterinary clinic with low blood pressure. The cat weighs 5 kg, and as the on call Vet you want to use a bag of saline to prepare a dopamine drip f

The Exine Layer It consists of two layers, inner (nexine) which is continuous and an outer (sexine) the sculptured one. The outer layer has ornamentations comprising rod-like

discovery of two light phase in photosynthesis

Define Importance of Nutrition in Human Body? Nutrition is increasingly being recognized as an important determinant, which modulates the biological process of ageing. Poor nut

Explain Direct Microscopic Count - Measurement of Microbes? The most obvious way to determine microbial number is through direct counting under a microscope. In this method, a

How many asymmetric carbons does the amino acid serine have? Please explain with a strucutral diagram if possible.

Q. What are the major purposes of the organic molecules for living beings? Ans. Organic molecules, like, lipids, carbohydrates and proteins perform several functions for

What are the cytokinins? And where are they made? The Cytokinins are phytohormones active in the promotion of cellular division they slow down the aging of tissues and act toge

Arterial Conduits LIMA UMA: anastomosis side-t-side with diaganal8 end-lo-sode with LAD Figure: Arterial conduits Internal Mamnrary Artery (IMA)

Why are some types of hemorrhagic diseases caused by genetic or acquired deficiency of the vitamin K metabolism? Lack of vitamin K predisposes to hemorrhages as this vitamin i