Blastocyst formation occurs after how many days of fertilization -
Ans. is 'b' i.e., 4-5 days o After fertilization, zygote divides and ultimately forms blastocyst at which stage it gets implanted in the endometrium.o After the zygote formation, typical mitotic division of the nucleus occurs producing two blastomeres.o Two cell stage is reached approximately 30 hours after fertilization.o The blastomeres continue to divide by binary division through 4, 8,16 cell stage until a cluster of cells is formed and is called morula, resembling a mulberry.o Morula after spending about 3 days in the uterine tube enters the uterine cavity through the narrow uterine ostium (1 mm) on the 4th day in the 16 - 64 cell stage.o While the morula remains free in the uterine cavity on the 4th and 5th day, it is covered by a film of mucus. The fluid passes through the canaliculi of the zona pellucida which separates the cells of the morula and is now termed blastocyst.o Implantation occurs on the 6th day which corresponds to the 20th day of regular menstrual cycle.
2-3 days
4- 5days
7-9days
8-11 days
Physiology & Histology