1) Adolescence and puberty :- a) Adolescence :- The period of life between 11 years and 19 years when the body undergoes changes leading to reproductive maturity is called adolescence. Between the ages of 11 years and 19 years children are called adolescents. During this period adolescents are called teenagers. b) Puberty :- During adolescence the body undergoes several changes and becomes capable of reproduction. These changes are the beginning of puberty.
2) Changes during puberty :- The important changes taking place during puberty are :- i) Increase in height. ii) Change in body shape. iii) Voice change. iv) Increased activity of sweat and sebaceous glands iv) Development of sex organs. v) Reaching mental, intellectual and emotional maturity. a)Increase in height :- By the age of 11 a boy reaches about 80% of his height and a girl reaches about 88% of her height. Initially girls grow faster than boys. By about 18 years of age both boys and girls reach their maximum height. Generally the height is similar to the parents because it depends on the genes inherited from the parents.
b) Change in body shape :- During puberty boys have broader shoulders and wider chests due to faster growth of muscles. In girls the breast begins to develop and the region below the waist becomes wider. c) Voice change :- During puberty in boys the voice box (larynx) becomes larger and is seen as a swelling in the throat called Adam’s apple and their voice becomes deep and hoarse. In girls the voice box is smaller and their voice is high pitched. Later their voice becomes normal. d) Increased activity of Sweat and Sebaceous glands :- During puberty the secretions of the sweat and sebaceous glands (oil glands) increases and many teens get acne and pimples on their face. e) Development of Sex organs :- During puberty in boys the testes and penis develops completely and produces sperms. In girls the ovaries develop completely and produces eggs.
f) Reaching Mental, Intellectual and Emotional maturity :- During puberty boys and girls mental, intellectual and emotional development takes place. They become more independent, self conscious and their way of thinking changes. 3) Secondary Sexual Characters :- Secondary sexual characters are the changes which takes place during puberty. In boys hairs begin to grow on the face and they develop beards and moustaches. Hair also grows in the chest, armpits and pubic region. The testes starts to produce sperms. In girls their breast develops and hair grows in the armpits and pubic region. The ovary starts to produce eggs. These changes are controlled by chemical substances called hormones produced by endocrine glands. The male hormone which controls secondary sexual characters is called testosterone. It is produced in the testes. The female hormone which controls secondary sexual characters is called estrogen. It is produced in the ovary. The production of these hormones is controlled by another gland called pituitary gland.
4)Reproductive phase in humans :- The capacity for reproduction starts at puberty. It lasts for a longer time in males than in females. In females the capacity for reproduction starts at puberty and lasts for 40-50 years. 5) Menstruation :- In females the ovary produces one egg every month and the uterus prepares to receive the fertilised egg. Its wall becomes thick with blood vessels. If fertilisation does not take place then the uterus wall breaks and comes out of the vagina as blood and mucous. This cycle takes place once every month and is called menstruation. The beginning of menstrual cycle is called menarch. When menstrual cycle stops at 40-50 years it is called menopause.
6) Sex determination in humans :- Human beings have 23 pairs of chromosomes in the nucleus of the cell. Out of this two chromosomes are sex chromosomes called X and Y chromosomes. The female has two X chromosomes and male has one X and one Y chromosome. The sperms and eggs have one set of sex chromosomes. Some sperms have X chromosome and some have Y chromosome. All eggs have X chromosome. If a sperm having X chromosome fuses with an egg having X chromosome the child will be a girl. If a sperm having Y chromosome fuses with an egg having X chromosome the child will be a boy.
7) Endocrine glands and their functions :- Endocrine glands produce chemical substances called hormones which controls different functions in the body. The main endocrine glands are :- Pituitary gland, Thyroid gland, Adrenal gland, Pancreas, Testes and Ovary. Pituitary gland :- controls growth and production of hormones by testes and ovary. Thyroid gland :- produces thyroxine. Its deficiency causes goitre (swelling of throat). Adrenal gland :- produces adrenalin. It helps the body to adjust to stress when we are angry or worried. Pancreas :- produces insulin. Its deficiency causes diabetes. Testes :- produces testosterone which controls production of sperms and secondary sexual characters in males. Ovary :- produces estrogen which controls production of eggs and secondary sexual characters in female.
8) Reproductive health :- To keep the body healthy everyone should have :- i) Balanced diet ii) Personal hygiene iii) Physical exercise Balanced diet :- is a diet which contains nutrients in the right amounts. Balanced diet should contain cereals, vegetables, fruits, pulses, milk, nuts, meat, eggs, sugar, jaggery etc. Personal hygiene :- Everyone should have a bath at least once everyday. If cleanliness of body is not done there can be bacterial infection and diseases. Physical exercise :- Walking, playing outdoor games and exercise keeps the body healthy.
9) Say “NO” to Drugs :- Drugs are addictive. If you take them once, you feel like taking it again and again. They ruin health and happiness. AIDS is a dangerous disease caused by the virus HIV. AIDS spreads from an infected person to a healthy person by :- i) Sexual contact. ii) Sharing syringes used for injecting drugs. iii) It is also transferred from the mother to a child through her milk.