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The placenta is formed by...

The placenta is formed by

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Placenta is a structural and functional unit of both chorionic villi and uterine tissue and it develops between the embryo (foetus) and the mother. The maternal and foetal blood do not mix with each other. They are seperated by the placental membrane.
e placenta consists of two essential portions : a maternal part of the placenta derived from the endometrium of the uterus and foetal membranes of the foetal part of the placenta. The maternal components of the Placenta are :
a) Uterine epithelium
b) Uterine connective tissue
c) Uterine capillary endothelium
The foetal components of the Placenta are :
a) Foetal capillary endothelium
b) Foetal connective tissue
c) Foetal chorionic epithelium.
The Placenta of human is called chorioallantoic placenta.as allantois fuse with chorion in the process of vascularisation. Placenta is discoidal as the Villi are restricted to the dorsal surface of blastodisc. Placenta is haemochorial as the maternal blood comes into direct contact with foetal chorion. During parturition the placenta is cast off with the loss of embryonic membranes and the encapsulating maternal tissues (decidua) causing extensive haemorrhage and there by bleeding. So, it is also called deciduate placenta.
Functions of placenta : 1. Supplies Oxygen and nutrients to the embryo.
2. Removes `CO_(2)` and exctory materials produced by embroyo.
Secretes Progesterone which is essential for maintenance of pregnancy after `4^(th)` month.
Secretes Oestrogens (mainly estradiol) that reach maternal blood and promote uterine growth and development of mammary glands.
Secretes Human Chorionic Gonadotropin (HCG) that is similar to luteinizing hormone is its action. This hormone is also used as indicator in the detection of pregnancy is early stages.
omatomammotropin secreted by placenta has an anti-insulin effect on the mother leading to increased plasma levels of glucose and aminoacids in the maternal circulation. In this way it increases the availability of these materials to the foetus.
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