NCERT Solutions for Class 8 Science Chapter 10 Reaching the Age of Adolescence

Ans : Hormones are chemical substances which are secreted by endocrine glands. They are responsible for changes taking place in the body. 

Ans : Adolescence is the time period between the beginning of puberty and adulthood. During this period, the body undergoes several changes alongside reproductive maturity. It begins around the age of 11 and lasts till 18 or 19 years of age. The period of adolescence may vary from person to person. 

Ans : Menstruation is the process of the shedding of the uterine lining on a regular monthly basis. It begins at puberty and is the reproductive cycle of the female body. Every month, the uterus prepares itself to receive a fertilized egg. Therefore, the inner lining of the uterus becomes thick and is supplied with blood to nourish the embryo. If the egg is not fertilized, then the lining of the uterus breaks down and gets released in the form of blood through the vagina. This lasts for about two to eight days. This cycle occurs every month and is known as the menstrual cycle. 

Ans : Changes at puberty:
(i) Sudden increase in height and weight.
(ii) Broadening of shoulders and widening of chest in boys, In girls, the region below waist becomes wider.
(iii) In boys, under the influence of hormones, the larynx becomes prominent, the vocal cords become longer and thicker. These changes cause the voice to become hoarse.
(iv) Appearance of hair in areas such as underarms, face, hands, and legs.
(v) Appearance of acne as a result of excessive secretion of oil from skin.
(iv) Testis grows and starts producing sperms in males, whereas in females, the ovary enlarges and starts producing matured eggs. 

Ans : Sex hormones are chemical substances produced by sex organs. For example, testosterone is the male sex hormone produced by the testis, and oestrogen is the female sex hormone produced by the ovary. These hormones affect the sexual features of an organism. Hence, they are known as sex hormones.
Functions of sex hormones:
Testosterone: This hormone brings about secondary sex characters in boys such as the growth of a beard, the voice becoming hoarse, development of reproductive organs, etc.
Oestrogen: This hormone is responsible for the development of secondary sexual characters in females such as the enlargement of breasts, development of female reproductive organs, etc.