Structure and

function of placenta

Structure of placenta

• At start of fourth month,placenta has 2 components:

• Fetal portion

• Maternal portion

• 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

• 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

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

• Exchange of nutrients: exchange of nutrients and

electrolyte takes place including amino acids ,free

fatty acids, carbohydrates and vitamins .

• It increases as pregnancy advances.

• 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.

• Hormonal production: by the end of fourth month

• Progesterone is produced 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