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Question
State in brief the changes that take place in a fertilized egg (zygote) till the birth of the child in human female reproductive system. What happens to the egg if it is not fertilized?
State in brief the changes that take place in a fertilized egg (zygote) till the birth of the child in human female reproductive system. What happens to the egg if it is not fertilized?
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Solution
1 During fertilization, the haploid nucleus of the sperm and ovum fuse to form a zygote. This zygote divides to form an embryo.
Development of an embryo inside the female body : The zygote formed after fertilization in the fallopian tubes is implanted in the uterus. The uterus is also known as the womb. Here, the zygote divides to form an embryo, which develops into a foetus.
The uterus is a sac-like structure which opens into the vagina. The wall of the uterus has three layers of tissues:
The outer-thin layer is known as the perimetrium.
The middle layer is thick and is made up of smooth muscles. It is known as the myometrium. These muscles contract strongly during the delivery of a baby.
The inner layer lines the uterine cavity, which has many glands and is known as the endometrium. It thickens every month and is supplied with blood to nourish the embryo. It undergoes cyclic changes during the menstrual cycle.
Therefore, the zygote in the uterus or womb divides many times to form an embryo. This embryo gets attached to the endometrium and is soon covered by rapidly dividing uterine cells. This leads to pregnancy.
2 If the egg is not fertilized, the endometrium (inner lining of the uterus) which is chiefly maintained for the implantation of fertilized egg gets degenerated and discharged from the uterus as menstrual bleeding.
Development of an embryo inside the female body : The zygote formed after fertilization in the fallopian tubes is implanted in the uterus. The uterus is also known as the womb. Here, the zygote divides to form an embryo, which develops into a foetus.
The uterus is a sac-like structure which opens into the vagina. The wall of the uterus has three layers of tissues:
The outer-thin layer is known as the perimetrium.
The middle layer is thick and is made up of smooth muscles. It is known as the myometrium. These muscles contract strongly during the delivery of a baby.
The inner layer lines the uterine cavity, which has many glands and is known as the endometrium. It thickens every month and is supplied with blood to nourish the embryo. It undergoes cyclic changes during the menstrual cycle.
Therefore, the zygote in the uterus or womb divides many times to form an embryo. This embryo gets attached to the endometrium and is soon covered by rapidly dividing uterine cells. This leads to pregnancy.
2 If the egg is not fertilized, the endometrium (inner lining of the uterus) which is chiefly maintained for the implantation of fertilized egg gets degenerated and discharged from the uterus as menstrual bleeding.
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