Ans. is a i.e. 500 gms The placenta at term Gross anatomy : It is a circular disc with diameter is 15 - 20 cms It is about 2.5 cm thick at the centre Weight is ,00 gmdeg Ratio of Weight of placenta : weight of fetus is 1 : 6deg it has 2 surfaces : Maternal surface Fetal surface It is formed by decidua basalis, It is formed by chorion frondosum and chorionic plate. Appears dull red in colour and is rough & The fetal surface is covered by blood vessels. spongy. It is divided into 15-20 lobes or cotyledons Placenta separates after the bih of baby and the line of separation is through decidua spongiosum. Human placenta is called as Discoid because of its shape, haemochorial because of direct contact of the chorion with maternal blood and deciduate because maternal tissue is shed at paurition. The stroma of the placenta has few phagocytic cell called as Hofbaeur cells." Extra Edge : I have already discussed formation of villi. For those interested in knowing : how placenta is formed from these villi : continue reading (but no question has been asked on it till yet). Development of placenta As pregnancy advances, villi on the embryonic pole grow and develop into the chorion frondosum, whereas villi on the opposite abembryonic pole degenerate. and this smooth chorion is called the chorion laeve. Similarly, the decidua overlying the chorion frondosum is called the decidua basalis, with large decidual cells full of glycogen and lipids. The decidua over the abembyronic pole is the decidua capsularis. The chorion frondosum along with decidua basalis forms the placenta. The formation of placenta begins in 6th weeks and is completed by 12th week.