09243500460  09243500460

Chapter-10: Reaching the Age of Adolescence


Which chemical substance is secreted by the endocrine glands which are responsible for the changes taking place in the body?


The chemical substance secreted by the endocrine glands is called Hormones. Hormones are responsible for the changes taking place in the body.



What do you mean by the term Adolescence?


The time period which comes between the beginning of adulthood and puberty is called Adolescence. In this time period the body undergoes different changes alongside reproductive maturity. It starts somewhat at the age of 11 and ends at the age of 18 or19. This period of adolescence may differ from person to person.



Define Menstruation.


The process of shedding of the uterine lining on regular monthly basis is called as menstruation. It starts at puberty and in the reproductive cycle of the female body. The uterus prepares itself to receive a fertilized egg on every month. Due to this the inner lining of the uterus become 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 get released in form of blood through vagina. The time period of this is about 2 to 8 days every month. This monthly cycle is known as menstrual cycle.



At the time of puberty what are the changes that takes place?


The changes that take place at the time of puberty are as follows:

  1. a) The height and weight of the body will suddenly increases
  2. b) The hair seems to be appear in the area such as legs, hands, face and underarms
  3. c) In female the enlargement of the ovary takes place and starts producing matured eggs and on the other hand in males the testis grows and starts producing sperms
  4. d) In males the shoulder broadens and chest become widen, whereas in females the region below the waist become wider.
  5. e) The acne is seems to appear because of the excessive secretion of the oil from the skin.
  6. f) In boys, the larynx become prominent under the influence of hormones, the vocal cord become longer and thicker. Due to this change causes the voice to become hoarse.



Draw a table that shows the name of the endocrine glands and the hormones secreted by them.


Endocrine Glands Hormones
Testis Testosterones
Ovary Oestrogen
Pituitary Growth hormone
Adrenal Adrenalin
Thyroid Thyroxin
Pancreas Insulin



What do you mean by the sex hormones? Why are the called so and state their function.


The chemical substances produced by the sex organs are called sex hormones. For example, in females the sex hormones produced by the ovary is called oestrogen and in males the sex hormones produced by the testis is called testosterone.

Some of the functions performed by the sex hormones:

Oestrogen: This hormone is responsible for the development of secondary sexual characters in females like enlargement of breasts, development of female reproductive organs etc.

Testosterones: this hormone brings the secondary sex character in boys such as the growing of beard, the voice become hoarse, development of the reproductive organs etc.



Pick the right one out:

a) The adolescents should take care of their diets, because:

i) they feel hungry during this age

ii) in teenagers the taste buds are well developed

iii) proper diet will develop their brains

iv) for the rapid growth in the body proper diet must be needed

b) the reproductive age in women begins when their

i) breast starts developing

ii) height increases

iii) menstruation starts

iv) body weight increases

c) The right meal for adolescents consists of:

i) rice, noodles and burger

ii) chapatti, dal, vegetable

iii) chips, noodles

iv) vegetable cutlets, chips and lemon drinks



a) The adolescents should take care of their diets, because:

iv) For the rapid growth in the body proper diet must be needed.

b) The reproductive age in women begins when their

iii) Menstruation starts

c) The right meal for adolescents consists of:

ii) Chapatti, dal, vegetable



Short notes of the following:

a) Secondary sexual character

b) Adam’s apple

c) Sex determination in the unborn baby


a) Secondary sexual character is the feature which differ males from female’s body. These can be the physical or behavioral characteristic that appears in them at the time of puberty.

In boys the secondary sexual characters are:

i) Beard and mustache grown up

ii) Chest hair grown up

iii) Hairs in the genital area grown up and other part of the skin

In girls the secondary sexual characters are:

i) Hairs in the genital area grown up and other body part

ii) The breast size increases and the skin of nipples present on the tip of the nipples started darkening.

b) Adam’s apple: In human males the larynx grows the larger at the time of puberty and can be seen as a protruding part of the throat. This protrusion is known as the Adam’s apple. In boys under the influence of sex hormones the larynx becomes prominent. Due to this the vocal cord becomes thicker and longer which causes the voice hoarse. On the other hand in females, the larynx is of small size and is hardly visible. Therefore, girls have a high pitched voice while the voice of the boys is low pitched.

c) Sex determination in the unborn baby

The fusion of the male gametes with the female gametes determines the sex of the baby. There are all 23 pairs of chromosomes in the nuclei of the human beings. The last pair among the 23 is known as sex chromosome.

The human male has 23 pair of chromosomes including XY sex chromosomes. Therefore the male gametes have 22 chromosomes and either an X or Y sex chromosome.

The male gametes can be of two types: 22+X or 22+Y

Females have 23 pairs of chromosomes including XX chromosomes. Therefore, their gametes can only have 22 chromosomes and one X sex chromosomes

The type of female gametes: 22+X


Thus, as the mother provides only X chromosomes, the sex of the baby is determined by the type male gamete (X or Y) that fuses with the X chromosomes of the female.



Word game; use the clues to work out the words.


  1. Protruding voice box in boys
  2. Glands without ducts
  3. Endocrine gland attached to brain
  4. Secretion of endocrine glands
  5. Pancreatic hormone
  6. Female hormone


  1. Male hormone
  2. Secretes thyroxin
  3. Another term for teenage
  4. Hormone reaches here through blood stream
  5. Voice box
  6. Term for changes at adolescence




  1. Adam’s apple
  2. Endocrine
  3. Pituitary
  4. Hormone
  5. Insulin
  6. Estrogen


  1. Testosterone
  2. Thyroid
  3. Adolescence
  4. Target site
  5. Larynx
  6. Puberty




The below table shows the data on likely heights of boys and girls as they grow in age. Draw a graphs showing height and age for both boys and girls on the same graph paper. What conclusion can be drawn from these graphs?



The above graph shows the relation between the age and height of both boys and girls. At the time of puberty there is a sudden increase in height of both boys and girls. On the basis of the above graph, it can be observed that during the age of 4-8 years, girls have less height as compared to boys. However, as soon as girl reach 12-13 years, their height shows a sudden increase and become more than boys. In later years, growth in both sexes becomes stable. Growth during puberty is under the control of hormones.



  1. shaile shaile
    March 19, 2018    

    so nice but you can’t explane
    i don’t want question&answers

  2. March 19, 2018    

    The oval shaped object found inside the scrotum

Leave a Reply

Your email address will not be published. Required fields are marked *

Join BYJU’S NCERT Learning Program

NCERT Solutions

NCERT Solutions Science