(a) When and how does placenta develop in human female?
(b) How is the placenta connected to the embryo?
(c ) Placenta acts as an endocrine gland. Explain.

Explanation

(a) After implantation, finger-Like projections called chorionic villi appear on the trophoblast that they are surrounded by the uterine tissue and maternal blood vessels. The chorionic villi and uterine tissue become interdigitated with each other and jointly form a structural and functional unit in between developing embryo fetus) and maternal body called placenta that acts as link between the foetus and mother
(b) The placenta is connected to the embryo through umbilical cord.
(c) The placenta secretes hormones like human chorionic gonadotropin (HCG). human placental lactogen (HPL), estrogen and progesterone, that are necessary to maintain pregnancy