The placenta serves several important functions: 1. It allows nutrients, gases, and waste products to be exchanged between the mother's and baby's bloodstreams through various transfer mechanisms like diffusion and active transport. 2. It anchors the developing embryo to the uterine wall for nutrition and growth. 3. The placenta also acts as an endocrine organ, secreting hormones to support the pregnancy.

1. FUNCTIONS OF
PLACENTA

2. • Histologically the placenta consists of barriers that prevent
the blending of blood of the foetus and mother. From the
maternal side the blood enters into the inter-villous spaces or
crypts through about 30 spiral arteries and at high pressure.
• The arterial blood rich in oxygen, nutrients etc. passes over
the villi in small fountain like streams and then under reduced
pressure settles down at the maternal base of the placental
compartment from where it is removed by open-ended uterine
veins

3. • On the foetal side blood enters the villi through the
branches of umbilical arteries. Although arterial, the
blood is poor in oxygen and high in carbon-dioxide
and other waste products. The foetal vessels at the
terminal end of the villi form capillary network and at
this region bulk of the placental exchange takes place.
The blood now richer, is placental villus drained back
to the foetus via the umbilical vein.

4. Exchange of substances from one blood stream
to the other, takes place by various transfer
mechanisms such as:
(i) Diffusion,
(ii) Active transport,
(iii) Pinocytosis and
(iv) Leakage (i.e., by breakage of placental
membrane).

5. The functions of placenta are as follows:
1. Anchorage:
• Placenta serves as adhesion or anchorage of the developing embryo with the uterine wall.
2. Nutritional Role:
• The foetus gets its nutrition from the maternal blood. Monosaccharide’s, lipids, amino acids, vita- mines and
hormones pass by diffusion or active transport. Macromolecules of polysaccharides, lipids and proteins are
absorbed by the trophoblast cells by pinocytosis. Water and electrolytes such as chlorides and phosphates of
sodium, potassium and magnesium pass by diffusion from mother to foetus.
3. Respiratory Role:
• Gaseous exchange takes place by diffusion across the foetal membrane. Oxygen diffuses from maternal blood
into the foetal blood, while reverse diffusion takes place in case of carbon dioxide.

6. 4. Excretory Role:
• Waste products like urea, uric acid and creatinine are eliminated via placenta, from the embryonic blood to the
maternal blood stream by diffusion. The kidney of mother removes these wastes of foetal metabolism along
with her own waste products.
5. Storage Function:
• Glycogen, fats and some inorganic salts are stored in the placenta to be utilized when diet of the foetus is
inadequate.
6. Enzymatic Function:
• Placenta produces various enzymes such as diamine oxidase, oxytocinase and phospholipase-A2, which
protects the foetus.
7. Endocrine Function:
• Placenta acts temporarily as an endocrine organ. It secretes many hormones such as estradiol, progesterone,
chorionic gonadotropin in most mammals and also placental lactogen in human female. In some animals, such
as rabbit, human females etc., the placenta is a significant source of relaxin, that relaxes the pelvic ligaments
to facilitate child birth.

7. 8. Immunological Role:
• Placenta acts as a barrier against the transportation of microbes into the embryo. However, antibodies which
have developed in the blood of a mother who has acquired immunity against certain diseases like diphtheria,
scarlet fever, small pox and measles are passed on to the foetus, who become passively immunized to these
illness in the first period after birth.
9. Destructive Function:
• Certain pathogenic organisms can penetrate through the placental barrier and infect the foetus. This occurs if
the mother is infected by those pathogens causing syphilis, small pox, chicken pox, measles and rubella.
Similarly any drug used during pregnancy can cross the placental barrier and cause disastrous effect on the
foetus.
• Thus, the drug thalidomide, taken as a sedative by ladies during early pregnancy, is found to be a teratogen
(i.e., it causes deformities in limb development, perforation of anus and development of a defective heart).
Children born to such mothers have flipper-like limbs and are called thalidomide babies.
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