Structure of Placenta
The placenta is a structure that creates a strong connection between the foetus and the mother. A number of finger-like projections known as chorionic villi develop from the outer surface of the chorion into the uterine tissue. These villi enter the mother’s uterine wall tissue to generate the placenta (Figure 1).
The placenta serves as a link between the foetal membrane and the inner uterine wall. Thus, the placenta contains both maternal and embryonic components. The growing embryo absorbs nutrition and oxygen from the mother through the placenta and emits carbon dioxide and nitrogenous waste.
Figure 1: Foetal membranes and placenta in late stage.
In the placenta, the foetal blood is in close proximity to the maternal blood, allowing for the exchange of materials. Food (glucose, amino acids, lipids), water, mineral salts, vitamins, hormones, antibodies, and oxygen are transferred from the mother blood to the foetal blood, while foetal metabolic wastes like as carbon dioxide, urea, and warn are transferred into the maternal blood.
Thus, the placenta acts as the foetus’ organ of nutrition, respiration, and excretion. The blood of the mother and foetus do not mingle anywhere, even the placenta. The blood of the foetus in the capillaries of the chorionic villi comes into intimate contact with the blood of the mother in the tissue between the villi; nonetheless, they are always separated by a membrane through which substances must diffuse or be transferred by some active, energy-demanding process.
The type of placenta in man is of described as deciduate (intimate contact between loetal and maternal tissue), discoidal (villi occur in the form of disc), haemo-chorial (chorionic epithelium in direct contact with maternal blood).
Functions of Placenta
Nutrition: Food materials pass from the mother’s blood into the foetal blood through the placenta.
Digestion: The trophoblast of the placenta digest protein before passing them into foetal blood.
Respiration: Through the placenta, oxygen travels from the mother blood to the foetal blood, while carbon dioxide travels in the opposite direction.
Excretion: Through the placenta, nitrogenous wastes such as urea flow from foetal blood to maternal blood, where they are filtered out by the mother’s kidneys.
Storage: Before the liver develops, glycogen, fat, and other substances are stored in the foetus’ placenta.
Barrier: The placenta serves as an effective barrier (defensive wall) that permits beneficial: aerials to enter the Social blood. Through the placenta, harmful chemicals like as nicotine from cigarettes and addictive narcotics such as heroin may pass. Therefore, pregnant women should abstain from smoking and using drugs. Pathogens may travel via the placenta.
Endocrine: As an endocrine gland, the placenta secretes hormones including oestrogen, progesterone, and human chorionic gonadotropin (HCG).
The gestation period or carrying period is the time between conception and delivery. It is around 280 days for humans. Following a full time of gestation, a kid is born. This is known as parturition. Before childbirth, the uterus undergoes a lengthy sequence of involuntary contractions known as “labour pains.” The umbilical cord is a blood vessel-containing tube connecting the abdomen of the growing embryo to the placenta of the mother. Its location in the infant is indicated by the navel.
Parturition signals are generated by the fully grown foetus and the placenta, which cause moderate uterine contractions known as the foetal ejection reflex. A complex neuroendocrine process causes parturition. When it’s time to birth the baby, the pituitary gland secretes adrenocorticotropic hormone (ACTH), which encourages the adrenal glands to release hormones.
These steroid hormones increase the production of prostaglandins by the placenta. The pituitary gland secretes the hormone oxytocin. These two hormones trigger the uterus to initiate forceful muscle contractions that gradually increase in strength over a period of 2 to 18 hours. During this moment, the cervix dilates completely and the amniotic sac ruptures.
The birth canal allows the infant to exit the uterus. The placenta is then ejected from the uterus shortly after. Labor pain may be intentionally created by injecting oxytocin or inserting prostaglandins into the vagina. When a woman is unable to tolerate the agony of childbirth, she might have a caesarean section performed.
Lactation is the process of producing and releasing milk (L. lactare = to suckle). Prolactin, an anterior pituitary hormone, increases breastfeeding following parturition. High doses of oestrogen act directly on the mammary glands and may inhibit prolactin stimulation. For 2-3 days following parturition, the mother produces colostrum, a thick, yellowish, high protein fluid.
Colostrum includes a high concentration of maternal antibodies and aids in the development of the baby’s immune system. Colostrum also serves as a laxative, eliminating foetal wastes known as meconium from the gut. Suckling causes the pituitary gland to produce oxytocin and prolactin. Oxytocin stimulates the secretion of milk from the mammary glands. Breast feeding throughout the newborn development phase is always suggested for raising a healthy kid.