Write the function of placenta.
Answers
The placenta performs the following functions:
1. Nutrition:
Food materials pass from the mother’s blood into the foetal blood through the placenta.
2. Digestion:
The trophoblast ol the placenta digest protein before passing them into foetal blood.
3. Respiration:
Through the placenta oxygen passes from the maternal blood to the foetal blood, and carbon dioxide passes from foetal blood to maternal blood.
4. Excretion:
Nitrogenous wastes such as urea pass from foetal blood into maternal blood through placenta and are filtered out by the kidneys of the mother.
5. Storage:
The placenta stores glycogen, fat etc. for the foetus before liver is formed.
6. Barrier:
Placenta functions as an efficient barrier (defensive wall) and allows useful: aerials to pass into the Social blood. Harmful substances such as nicotine from cigarette and addictive drugs such as heroin can pass through placenta. Therefore, pregnant women should avoid cigarette and drugs. Viruses and bacteria can pass through placenta.
7. Endocrine function:
Placenta functions as an endocrine gland it secretes hormones such as oestrogen, progesterone and human chorionic gonadotropin (HCG).
The placenta is the highly specialised organ of pregnancy that supports the normal growth and development of the fetus. Growth and function of the placenta are precisely regulated and coordinated to ensure the exchange of nutrients and waste products between the maternal and fetal circulatory systems operates at maximal efficiency. The main functional units of the placenta are the chorionic villi within which fetal blood is separated by only three or four cell layers (placental membrane) from maternal blood in the surrounding intervillous space. After implantation, trophoblast cells proliferate and differentiate along two pathways described as villous and extravillous. Non-migratory, villous cytotrophoblast cells fuse to form the multinucleated syncytiotrophoblast, which forms the outer epithelial layer of the chorionic villi. It is at the terminal branches of the chorionic villi that the majority of fetal/maternal exchange occurs. Extravillous trophoblast cells migrate into the decidua and remodel uterine arteries. This facilitates blood flow to the placenta via dilated, compliant vessels, unresponsive to maternal vasomotor control. The placenta acts to provide oxygen and nutrients to the fetus, whilst removing carbon dioxide and other waste products. It metabolises a number of substances and can release metabolic products into maternal and/or fetal circulations.
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