Best Concept Of Fertilization And Development Of Embryo
The fusion of male gamete (sperm) with the female gamete (egg or ovum) is called fertilization. Millions of sperms are transferred into the female and the sperms swim into the uterus reaching the oviduct. If an egg from the ovary has also reached the oviduct, ONLY one of the sperms may fuse (unite) with it forming a zygote (oospore). The uniting sperm loses its tail outside and only its head enters the egg. The rest of the sperms degenerate. The fusion of sperm and the egg is called fertilization. The zygote then moves into the uterus and gets attached to the endometrium (spongy cushion) on its wall.
In human beings and in animals such as cats, dogs, cows, and hens fertilization takes place inside the body of the female. Fertilization taking place inside the body of the female is called internal fertilization.
In Vitro Fertilization, The Test Tube Baby
Some women are unable to bear babies because of certain defects or deficiencies. The defect may be less number of sperms or weak sperms from male or blockade of passage to oviduct (fallopian tube) in the female. The result is that the sperms fail to fertilize the ovum (egg). In such cases, doctors collect freshly released egg from the mother and keep it in the company of sperms from the father for a few hours in a Test-tube with proper nutrition base under a suitable temperature. During this time fertilization may take place outside the body of the mother. This is called in vitro fertilization. Zygote, thus formed, develop for about a week after which it is transferred to the mother’s uterus where complete development of a baby takes place. Babies reproduce through this technique are called test-tube babies.
It is in human beings that normal fertilization is internal. It is only under special situations that the ovum (egg) is made to fertilize in a test-tube outside the mother’s body, hence the name. Otherwise, the development and the birth of this baby is as normal as in any other case. Naming it as “Test-tube baby” is perhaps wrong. We have learned that in many animals fertilization is external.
Development Of Embryo
The embryo is the baby in the early stages of formation. You have learned in flowering plants that the embryo is the ‘baby plant’ which stays inside the seed till its growth into an adult plant after the germination of the seed.
Similarly, in the case of man and many animals embryo remains within the body of the mother. It is only the baby (fully developed embryo) which takes birth.
How do babies develop inside the mother
The zygote formed as a result of fertilization divides and divided into a ball of 2481632 and into numerous cells. The cells inside the ball start getting differentiated into organs of a baby forming young embryo. By this time, the embryo gets attached to the wall of the uterus from where it starts drawing nutrition through a cord (called the umbilical cord) in the form of blood. The point of attachment of the cord to the wall of the uterus is called the placenta. By the time embryo is five weeks old it will have rudimentary eyes and a beating heart. By the time it is twelve weeks old it is a miniature baby.
It takes about 280 days for the embryo to grow into a ‘baby’. This period of growth of the embryo to a baby inside the mother’s womb is called”pregnancy”, and the embryo including the baby during pregnancy is called a fetus. when the fetus is complete with all the organs, the mother gives birth to a baby.
