How do Organisms Reproduce? | Class 10 CBSE | Web Notes | Part 4 - Sexual Reproduction in Human Beings
REPRODUCTION IN HUMAN BEINGS
In early teenage years, the appearance and proportions of the body change, and new features and sensations appear. These changes indicate sexual maturation.
All these changes occur slowly and gradually.
The pattern and duration of these changes vary among different people, resulting in different patterns of hair growth, size, and shape of breasts or penis.
Up to the adult stage, the body's resources are mainly used for growth, not for maturation. Then the growth rate slows down, and reproductive tissues begin to mature. This period during adolescence is called puberty.
Changes during puberty are signals of sexual maturity so that other individuals can identify them for mating.
Changes Common to Boys and Girls
Thick hair grows in armpits and the genital area, which becomes darker in color.
Thinner hair appears on legs, arms, and face.
Skin frequently becomes oily, which may cause pimples.
Changes in Girls
Breast size increases, and the skin of the nipples darkens.
Menstruation begins.
Changes in Boys
Thick hair grows on the face.
Voice begins to crack.
Erection of the penis occurs during daydreams or at night.
(a) Male Reproductive System
It consists of two testes and ducts to deliver germ cells.
Male reproductive system
Testes: In these, germ cells (sperms) are formed.
Testes are located in the scrotum because sperm formation requires a lower temperature than body temperature.
Testes also secrete a hormone, testosterone, which regulates the formation of sperms and changes in boys during puberty.
Ducts: Include the vas deferens to deliver sperms, which unites with the urethra coming from the urinary bladder. Thus, the urethra forms a common passage for sperms and urine.
Along the path of the vas deferens, glands like the prostate and seminal vesicles release fluid secretions. These are mixed with sperms to form semen, which makes sperm transport easier and provides nutrition.
A sperm consists of genetic material and a long tail that helps it move toward the female germ cell (egg).
(b) Female Reproductive System
It consists of two ovaries, two oviducts, uterus, vagina, etc.
Female reproductive system
Female germ cells (ovum or egg) are made in the ovaries. They also produce some hormones.
The ovaries of a newly born girl contain thousands of immature eggs. At puberty, some of them start maturing. One egg is produced every month by one of the ovaries. It is carried from the ovary to the womb (uterus)—elastic and bag-like—through a thin oviduct (fallopian tube).
The uterus opens into the vagina through the cervix.
During sexual intercourse, sperms are transferred into the vagina through the penis.
Sperms travel from the vagina via the uterus to reach the oviduct, where they meet the egg, leading to fertilization. This forms a zygote (fertilized egg), which divides to form an embryo. The embryo implants in the lining of the uterus, where growth continues, and organs develop into a foetus.
The uterus prepares every month to receive and nurture the embryo. The lining becomes thick and spongy with a rich blood supply to nourish the embryo.
Placenta: This is a disc of special tissue embedded in the uterine wall, connecting the foetus to the mother. It contains villi on the embryo’s side, surrounded by blood spaces on the mother’s side. Villi increase the surface area.
Functions of Placenta
The embryo gets nutrition from the mother’s blood.
Transports glucose and oxygen from the mother to the embryo.
Removes wastes from the embryo into the mother’s blood.
Development of the child inside the mother’s body takes about 9 months. The child is born as a result of rhythmic contractions of the muscles in the uterus.
What Happens When the Egg is Not Fertilized?
If the egg is not fertilized, it lives for about one day.
The lining of the uterus slowly breaks and comes out through the vagina as blood and mucus. This cyclic process occurring every month is called menstruation. It lasts for 2-8 days.
Reproductive Health
A woman’s body and mind should be ready for sexual activity, pregnancy, and bringing up children. If not, her health will be adversely affected.
There are many sexually transmitted diseases, e.g., gonorrhoea and syphilis (bacterial infections) and warts and HIV-AIDS (viral infections). They can be prevented by using a condom for the penis during sex.
Contraceptive Methods to Avoid Pregnancy
Mechanical barriers: They prevent the meeting of sperm with the egg, e.g., condoms or coverings worn in the vagina.
Oral pills: They change the hormonal balance of the body, so eggs are not released, and fertilization does not occur. They have side effects due to hormonal imbalance.
Loop or copper-T: These are placed in the uterus to prevent pregnancy. They cause side effects due to irritation of the uterus.
Surgical methods: Fertilization is prevented by blocking gamete transport. In males, the vas deferens is blocked to prevent sperm transfer. In females, the fallopian tube is blocked to prevent the egg from reaching the uterus. Surgical methods have long-term safety but can cause infections and other problems if not performed properly.
Surgery can also be used to remove unwanted pregnancies. However, it is misused for illegal sex-selective abortion (female foeticide). Due to this, the female-male sex ratio has declined, so prenatal sex determination is prohibited.
By reproduction, the population is increased. The birth and death rates in a given population determine its size. Population explosion adversely affects people’s standard of living. However, inequality in society is the main reason for poor standards of living.
