NCERT solutions are given in a step-by-step manner to help students understand each concept easily. Diagrams are included for better understanding and easy visualization.
CBSE NCERT Solutions for Class 8 Science Chapter 10:
What is menstruation? Explain.
Menstruation is the process of the shedding of the uterine lining on a regular
monthly basis. It is the reproductive cycle of the female body and begins at puberty. Every month, the uterus prepares itself for implantation of a fertilised egg. Therefore, the inner lining of the uterus becomes thick and is supplied with blood to nourish the embryo. If the egg is not fertilised, then the lining of the uterus breaks down and is released in the form of blood through the vagina. The whole process lasts for about two to eight days. This cycle occurs every month and is known as the menstrual cycle.
List changes in the body that take place at puberty.
Changes at puberty:
- Sudden increase in height.
- Broadening of shoulders and widening of chest in boys. In girls, the region below
waist becomes wider.
- At puberty, the voice box or the larynx begins to grow. Boys develop larger voice
boxes. The growing voice box in boys can be seen as a protruding part of the throat
called Adam’s apple. In girls, the larynx is hardly visible from the outside because of its small size. Generally, girls have a high pitched voice, whereas boys have a deep voice.
- In girls, breasts begin to develop at puberty and boys begin to grow facial hair, that is, moustaches and beard. Boys also develop hair on their chest. In both, boys and girls, hair grows under the arms and in the region above the thighs or the pubic
- Appearance of acne as a because of the increased activity of sweat glands and
sebaceous glands in the skin.
- Testis grows and starts producing sperms in males, whereas in females, the ovary
enlarges and starts producing matured eggs.
What are sex hormones? Why are they named so? State their function.
Sex hormones are the hormones that control the development of secondary sexual characteristics and also regulate the proper functioning of the sex organs. They are
named so because they are produced in both males and females by the respective sex
organs under the regulation of the pituitary gland.
Functions of sex hormones:
→ Testosterone: This hormone secreted by the testes brings about secondary sex characters in boys such as the growth of a beard, the voice becoming hoarse, development of reproductive organs, etc. It also serves to regulate the sperm production
→ Oestrogen: This hormone secreted by the ovaries is responsible for the development of secondary sexual characters in females such as the enlargement of breasts, development of female reproductive organs, etc. It also serve to regulate the egg production in females