HUMAN BIOLOGY

Human Reproductive Systems

Human Reproductive System

Q1) Development of the Fetus

Fertilization - 3rd Month

The fertilization starts with the penetration of the sperm into the ovum that is residing in one of the fallopian tube. The sperm loses its tail and then change itself into the nucleus and combines with the nucleus of the female egg. This joining makes a complete cell with 46 chromes and is known as zygote. Within the few hours of union the zygote starts to multiply first two then four and so on. In three days this zygote multiplied so much that it becomes a sphere of cells, visible through microscopes and is known as Blastocyst. This Blastocyst reaches the uterus and implants to the endometrium. This is the end of the fertilization. After the fertilization takes place the next step is the development of the placenta. After 1 month the embryo is 0.25 inch long and has its circulation system.

In the second month the facial features begins to develop. Tiny bud grows for the formation of the legs and arms. Digestive tract, sensory organs and bone formation starts. At the end of the month the embryo is of 1 inch in length, with well-formed neural tube.

In the start of the third month the embryo is totally converted into the fetus, with fully developed arms, fingers, hands and legs. Nails, teeth and reproductive organs start to develop. By the end of the third month the fetus is about 4 inch long with its urinary and circulatory system.

4th Month - 6th Month

In the 4th month the eyelids, eyelashes, toes, reproductive organs and genitalia of the fetus are fully developed. The heartbeat is now audible and the fetus can make faces and yawn.

In the 5th month the baby starts to move and his/her movement can be felt. Hair begins to grow on head and other parts of the body. At the end of the 5th month the fetus is about 10 inches long.

In the 6th month of the pregnancy the skin of the fetus turns reddish, but the veins are visible through it. Eyes begin to open and the finger prints are distinguishable. The fetus starts responding to the sound. If born at this time the baby can survive but intensive cure is needed.

7th Month - Parturition

The baby will remain developing and maturing. He/she can changes his/her position often in response to the heat, light, pain, sound and so on. ...