The nomal weight of Placenta at term pregnany is:
Ans. B. 500 gm. (Ref. Textbook of Obstetrics D.C. Dutta 7th Ed pg. 29)Human placenta:# Only eutherian mammals posses placenta. It is an endocrine gland.# Discoid shape# HaemochorialQ# Fetal component develops from the chorion frondosum.Q# Maternal component develops from decidua basalis.Q# Placental development begins at 6th week and is completed by 12th week.# Placenta at term:# diameter 15-20 cm and 3 cm thick# weighs 500 gm# Occupies 30% of the uterine wall at term.- the proportion of weight of baby being roughly 1:6 at term.- At term, about 4/5th of the placenta is of fetal origin.- Maternal surface is rough and spongy and is mapped out into 15-20 cotyledons.# Separation:- placenta separates after the birth and the line of separation is through the decidua spongiosum.Educational points:# The umbilical cord develops from the band of Mesoblastic tissue stretching between the embryonic disc and the chorion. It is lined by a single layer of amniotic epithelium but shows stratification like that of fetal epidermis near term.# It contains Wharton's jelly formed by mucoid degeneration of extraembryonic mesodermal cells. Of the two umbilical veins, the right one disappears by the 4th month, leaving behind one vein which carries oxygenated blood from the placenta to the fetus. The proximal part of Vitelline duct may persist as Meckel's diverticulum. Allantois is a blind tubular structure that may be occasionally present near fetal end which is continuous inside with the fetus with its urachus and bladder. In early period, intraembryonic coelom is continuous with extraembryonic coelom along the herniation of coils of intestine (mid gut). The condition may persist as congenital umbilical hernia or exomphalos.# The umbilical cord is 40 cm in length (range 30-100 cm). Its diameter is 1.5 cm. False knots are found which are kinkings or collections of Wharton's jelly. True knots (1%) are rare. The umbilical arteries do not posses an internal elastic lamina but have got well developed muscular coat. Both the arteries and the vein do not posses vasa vasorum.
300 gm
500 gm
800 gm
1500gm
Miscellaneous (Gynae)