Placenta is defined as temporary intimate mechanical and physiological connection b/w foetal and maternal tissues for the nutrition, respiration, and excretion etc. of foetus.
- Surface of blastocyst gives rise to finger like outgrowth called chorionic villi, finally chorionic villi fuse with eroded uterine mucosa to form a true placenta. Placenta is fully formed in 10 weeks and lasts through out the pregnancy. Human placenta is haemochorial placenta in which all three maternal tissues of the placenta (uterine epithelium, endometrial mesenchymal connective tissue and endothelium of maternal blood capillaries) have been digested by trophoblast of chorionic placenta.
- Human placenta is deciduate placenta because at the end of pregnancy some maternal tissue called deciduas is expelled.
- Placenta help in nutrition.
- Placenta help in respiration.
- It also helps in excretion.
- It act as endocrine gland, it secretes HCG and HPL, HCG help to maintain the corpus luteum for continuous secretion of progesterone to maintain the pregnancy at the end of gestation period, and it also produces the relaxin. Which helps in softening of pubic at time of child birth?
- Antibodies against diphtheria, smallpox, measles etc. passes from maternal blood to foetal blood through placenta thus provide passive immunity.
- It stores glycogen till the formation of liver.
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