Placenta it's formation and functions class 12th Biology by anshul sharma

Implantation or nedation of blastocyst in to uterine wall leads to pregnancy.
After implantation finger like projection called chorionic Villi appears on the trophoblast.
The chorionic Villi are surrounded by uterus tissue and maternal blood. It causes the chorionic Villi and uterine tissue to become interdigitated with each other and jointly form a structural and functional unit between developing foetus and maternal blood called placenta.
" Placenta is an vascular connection between foetus and maternal blood."
Type of placenta in human-1. On the basis of histology human have haemochorial placenta
2. On the basis of extra embryonic membrane human have chorionic placenta.
Functions perform by placenta-
I. placenta supply oxygen and nutrients to the developing foetus and removes the carbon di oxide and excretory waste from foetus.
II. Additionally the placenta function as a endocrine gland. It produce several hormones such as human chorionic gonadotropin (HCG), human placental lactogen (hPL), oestrogen, progesterone etc.
III. Some antigen and virus, drugs can also pass through placenta.
[ Presence of HCG is detected by pregnancy kit in urine of female and confirm pregnancy]
Placenta is connected to the embryo by umbilical cord. The embryo transport nutrients and waste to and from the placenta through the umblical cord.
Later in pregnancy relaxin is also produce by ovary. It causes the relaxation of pelvic ligament and facilitate the child birth.
Relaxin, HCG hPL are only released during pregnancy.
During pregnancy production of another hormones is increased. These hormones include oestrogen, progesterone, cortisol, thyroxine, prolactin etc. High level of these hormones are essentiall for supporting foetal growth, metabolic changes in pregnancy as well as maintenance of pregnancy.

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