Human Reproduction-Concept

Human Reproduction-Concept

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Testes

1. Testes are the primary reproductive organs in the males. They are located in a pair in the scrotal sac outside the abdomen. They are endocrine in nature.

2. In the embryo stage the testis are inside the abdomen and descend out shortly before birth as high temperature of the body is not good for sperm maturation.

3. The testis is a capsule-like structure consisting 15-20 segments. Each segment contains seminiferous tubule and interstitial cells.

4. The sperms are produced in seminiferous tubule by the process of spermatogenesis.5. The interstitial cells act as a packing between the seminiferous tubules and produce the male hormone testosterone.
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Female reproductive system – Ovaries

1. Ovaries are the primary reproductive organs in the female. They are located in a pair in the abdomen. Ovaries are endocrine in nature.
2. They produce eggs i.e the female gamete.
3. The cellular sac which contains a mature egg is called the follicle which gets filled with fluid and enlarges as the egg grows large. It is called the Graaffian follicle.
4. It ripes and expands over the surface of the ovary. In the process of oogenesis, the ovaries produce a mature egg.3

Spermatogenesis

1. The process of formation of sperms is called spermatogenesis.
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Oogenesis

1. The process of formation of a mature female gamete is called oogenesis.
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Process of fertilization in human beings

1. The process of union of male gamete and the female gamete to form zygote is called as fertilization.
2. The sperms are ejaculated in the female vagina near the cervix during copulation. A single ejaculation contains four hundred million sperms, which actively swim by their tails into the uterus at the rate of 1.5mm per minute.
3. They reach the oviducts from the uterus and one sperm fertilizes the egg.
When the sperms reach the oviducts several sperms surround the egg but only one gets the entry in it.
4. The head part of the sperm which contains nucleus enters the egg and the tail is left behind. There is fusion of sperm nucleus and egg nucleus in the process of fertilization.
5. After fertilization the entry of other sperms is prevented by chemical barrier.
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Menstruation

1. The start of the period or the menstrual cycle is counted from the day of onset of blood flow to the next onset after 28 days.

2. It involves the menstrual phase, ovulatory phase, follicular phase and luteal phase.

3. The menstrual phase lasts for 3 to 5 days involving the discharge of blood.

4. In the follicular phase there is the secretion of hormones that make the uterus ready to receive a fertilized egg and nourish the embryo.

5. Ovulatory phase involves rupture of the follicle and release of eggs on about the 13th or 14th day.

6. Luteal phase involves the thickening of the uterus wall and the formation of hormone-producing corpus luteum. It lasts from 15 to 28 days.7

Process of fertilization in human beings

1. The process of union of male gamete and the female gamete to form zygote is called as fertilization.
2. The sperms are ejaculated in the female vagina near the cervix during copulation. A single ejaculation contains four hundred million sperms, which actively swim by their tails into the uterus at the rate of 1.5mm per minute.
3. They reach the oviducts from the uterus and one sperm fertilizes the egg.
When the sperms reach the oviducts several sperms surround the egg but only one gets the entry in it.
4. The head part of the sperm which contains nucleus enters the egg and the tail is left behind. There is fusion of sperm nucleus and egg nucleus in the process of fertilization.
5. After fertilization the entry of other sperms is prevented by chemical barrier.
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Implantation

1. The zygote formed after the process of fertilization divides into 2, 4, 8, 16 cells. It forms a small fibrous ball of cells called blastocysts till it reaches the uterus and forms a pit in the endometrium wall.

2. It gets fixed there for about a week after ovulation and this process is called implantation.9

Pregnancy

1. When the unborn baby is still inside the body of the mother that state is known as pregnancy.
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Parturition

1. When the process of gestation is completed by the embryo which is about 280 days its time for process of birth of the baby.

2. At the time of birth there are powerful contractions of the muscles of the uterus and the baby arrives with the head first out.

3. After the birth of the infant the blood vessels in the umbilical cord shrink. They are tied in a knot and cut. After a while, the placenta breaks from the uterus and is expelled out.4. The uterus regains its normal shape after some days.
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Placenta

1. A placenta is a disc like structure which acts as a connection to the wall of the uterus. 

2. The main function of the placenta is to provide the 8 weeks old foetus with food and oxygen. The placenta also removes the carbon dioxide and nitrogenous waste produced by the foetus.

3. The umbilical cord connects the placenta with the foetus.

4. The placenta is made up of finger like projections called the villi which are available in pairs. One set is given out from the wall of the uterus and another is an extension from the embryo.

5. The two sets are interlocked but never open into each other. The blood of embryo comes very near by but never mixes with the blood of the mother.

6. The placenta diffuses substances like oxygen and nutrients like glucose, amino acids, vitamins and mineral ions from mother to the foetus.7. From foetus, it eliminates carbon dioxide and urea to the mother for elimination. They also perform endocrine functions.
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Development of human embryo

1. There are many stages involved in the development of the embryo.

2. The unfertilized egg which is released from the ovary after fertilization forms a zygote. The single celled zygote divides to to form a spherical mass of cells called the morula.

3. The morula then divides to form a blastocyst which is a hollow sphere with a surrounding single layer called the trophoblast and cells are projecting from inside. The blastocysts get attached to the wall of the uterus.

4. The three weeks old embryo appears to be a small organism. After five weeks heart and blood vessels are developed. After the course of eight weeks, there is the formation of limbs and the organisms start taking the appearance of a human being.5. An infant is born in the end after the completion of 40 weeks.