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
Define Obligatory Nitrogen losses? The Committee estimated the total obligatory nitrogen losses through faeces, urine, skin and other miscellaneous routes in adult men as 2.0 m

What proportion of children with Down syndrome do you expect when women with down syndrome have children with men who have 46 chromosomes Justify your answer

Why can the amnion also be considered an adaptation to terrestrial life? The amnion is also an adaptation to dry land since one of its functions is to prevent desiccation of th

Concerning their biological function what is the difference between mitosis and meiosis? The major biological function of mitosis is cellular multiplication, a fundamental proc

In an adult male, which of the following is true? A. The plasma membranes of Leydig cells contain LH receptors. B. The plasma membranes of Sertoli cells contain FSH receptor

SKI N GRAFTING - Skin for grafting is taken from another part of body of the same persons. Now it is possible to grow a sheet of skin in culture from a small piece of skin

C o w - po x (vaccinia) E p idemiology: This infection, although mostly occurring in cows, sometimes also occurs in buffaloes. Under natural conditions, t

Is it more indicated for a geneticist desiring to map the X chromosome of the mother of a given family (the researcher does not have access to her DNA, only access to the genetic m

Determine about the diseases Sleep attacks These are brief, often irresistible, episodes of sleep, probably slow wave, NREM, naplike sleep that last about 15 minutes and can oc