how does a foetus develop from a single cell ?
Asked by divyalakshmi | 24th May, 2010, 11:42: PM
The zygote first divides into two identical cells, called blastomeres. They continue to subdivide once every 12 to 20 hours as the zygote slowly passes down the fallopian tubes. About 3 days after conception, the zygote consists of 16 cells and is called a 16 cell morula. It then migrates from the fallopian tube to the uterus. Seven days after conception, the zygote burrows itself into the plump uterine lining, a process called implantation. The zygote is now known as a blastocyst. It starts to produce hormones and also develops a primitive streak, which will later develop into the fetus' central nervous system. The pre-embryo is now referred to as an embryo. It is a very small cluster of undifferentiated tissue at this stage of development. After 3 weeks, the rapidly dividing cells of the embryo are in the process of forming the various body systems, including the digestive system. Gradually the hand and leg buds form, the tail is lost, heart begins to beat and brain begins to develop. The embryo develops its placenta and amniotic sac. The placenta is burrowing into the uterine wall to access oxygen and nutrients from the mother’s bloodstream. The tiny muscles allow the embryo to start moving about. Blood cells are being made by the embryo’s liver. At around 10 weeks, the embryo develops into a stage with noticeably human features and is now known as a foetus. It is about 2.5cm in length and all of the bodily organs are formed.
Answered by | 28th May, 2010, 07:10: AM
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