placenta

Placenta structure and function

1. Structure and function o f plac enta By Dr. Priti D.Diwan Assistant Professor Department of Zoology J.D.Patil Sangludkar Mahavidyalay Daryapur .

2. Structure of placenta At start of fourth month,placenta has 2 components: Fetal portion Maternal portion

3. On fetal side the placenta is bordered by chorionic plate and on its maternal side by decidual plate In the junctional zone , trophoblast and decidual cells intermingle .it consists of giant syncitial and decidual cell At this stage most of the trophoblasts cells have been degenerated

4. Between the two chorionic and decidual plates are the intervillous spaces which consists of maternal blood in it. During the fourth and fifth month Decidua forms decidual septa which project into intervillous spaces but NOT reach the chorionic plates Due to this septum placenta is divided into a number of compartments called cotyledons

5. Function of placenta EXCHANGE OF GASSES: oxygen , carbondioxxide and carbon monooxide takes place by diffusion. at term fetus extracts 20-30ml of oxygen per minute from maternal circulation Even a short term interruption of oxygen supply is fatal to fetus

6. Exchange of nutrients: exchange of nutrients and electrolyte takes place including amino acids ,free fatty acids, carbohydrates and vitamins . It increases as pregnancy advances.

7. Transmission of maternal antibodies: immunoglobulins consists of entirely maternal immunoglobulins G(IgG), which begins to be transported from mother to fetus at approximately at 14 weeks. Via this the fetus gains passive immunity against various infectious disease .newborns begin to produce their own IgG but adult levels arenot achieved until at the age of 3.

8. Hormonal production: by the end of fourth month Progesterone is pr oduced by placenta in sufficient amount to maintain pregnancy. Estrogenic hormone is produced just before the end of pregnancy . Human chorionic gonadotropin is excreted by mother ,its presence is indicator of pregnancy Somatomamotropin it’s a growth like hormone