In this article we will discuss about the functions of placenta.
i. Respiratory:
Since fetus is not exposed to the outside atmosphere, the fetal lung will be in solid state. The oxygen requirement by the developing fetus and removal of carbon dioxide from the fetal body should be taken care off by the maternal blood. Hence placenta acts as a structure across which these gases can get exchanged. It acts as a fetal lung.
ii. Excretory:
Excretion of metabolic waste products, like urea, uric acid and creatinine from fetal to maternal blood, since fetal kidney is non-functional.
iii. Nutritive:
Nutrients, like glucose, free fatty acids, get diffused from maternal to fetal blood to meet the demands of the developing fetus. At the same time, the placenta itself acts as fetal liver and synthesizes proteins, since the most of the proteins of mother cannot cross placenta to reach the fetal circulation.
iv. Protective:
It prevents transport of certain bacteria and viruses and prevents infection of the developing fetus even though mother may be suffering from the disease.
v. Endocrine (Figs 7.19, 7.20):
It secretes many of the hormones, namely:
a. hCG
b. Estrogen
c. Progesterone
d. Human chorionic somatomammotropin.
hCG is required to maintain the corpus luteum till placenta per se is able to secrete adequate amount of estrogen and progesterone to maintain the gestation. Normally, it takes about 3 months for the placenta to secrete the required amount of progesterone and estrogen for maintenance of pregnancy.