Functions of the Placenta

Functions Of The Placenta

1.           Respiratory: During intrauterine life no pulmonaryexchange of gases can take place. The fetus absorbs oxygen from the maternal haemoglobin by processes of simple osmosis and diffusion and gives off carbon-hydroxide into the maternal circulation similarly.

2.           Nutritive: All food nutrients required by the fetus for growthand energy are obtained from the mother’s blood in simplest form. Protein for building tissue, glucose for growth and energy, calcium & phosphorus for the bones and teeth, water, vitamins, electrolytes, iron and other minerals for blood formation, growth and various body processes. The Placenta does the selection. The placenta also does the metabolic function of glucose; it stores it as glycogen and converts it to glucose as required.

3.           Excretory: All waste products from the fetus are excretedinto the mother’s circulation through the placenta.

4.           Endocrine: Placenta produces some hormones.

·              Human Chorionic Gonadotrophin (HCG): This is a unique hormone in pregnancy produced by the langhans cells of the chorionic villi – cytotrophoblast from  its earliest day. It  makes the  corpus luteum to continue with production of progesterone and Oestrogen until the placenta takes over. It can be detected from about the 30^th day of conception and reaches its peak about 60-80 days of pregnancy. The peak drops at about the 12^th week and a low level is maintained throughout pregnancy. The high level persist longer in multiple pregnancy, trophoblastic tumour (hydatidiform mole). It is excreted in urine and form the basis for immunological test for diagnosing pregnancy. It also regulates the production of oestrogen by the placenta.

·              Progesterone: This is produced in the syncytial later bythe placenta from about the 3^rd month. It relaxes the smooth muscles and reduces exertibility tone e.g. uterus, stomach ureter and intestines. It is excreted in urine as pregnanediol. The level drops immediately before the onset of labor.

·              Oestrogen: Oestroil, oestradiol. It is produced by fetoplacenta unit from the 6^th week. It aids the growth of the uterine muscle and mobility of the nipple. The amount rises steadily until term and falls when the palcenta is expelled to allow prolactin to initiate lactation. The amount of the measured urine or serum eastroil indicates fetal well being.

·              Human placenta Lactogen (HPL): Aids thedevelopment and growth of the breast. Has generalized metabolic effect on carbohydrate and lipids. It has connection with the activity of the growth hormone. The level of it in the blood reflects placental function.

5.           Storage: It stores glucose in form of glycogen until the liverof the fetus is matured enough and capable of storage. Vitamins A & D and iron are also stored in the placenta.

6.           Protective: The placenta protects the fetus from someharmful diseases suffered by the mother e.g. malaria and T.B. Organisms can not pass through the placental barrier. But some bacteria and virus e.g. syphilis, rubella (German measles), small pox may, and cause congenital abnormalities and some drugs (morphine, Pethidine, heparin etc) can pass through and affect the respiratory centre. Penicillin and sulphonamides can also pass through but this serves as an advantage in syphilis. Antibodies, immunoglobulin G (IgG) confer immunity for the first 3 months of life.