Chapter 9 CLASS 8TH Reaching the age of Adolesence (1)
- 1. Chapter 10 Notes: Reaching The Age Of Adolescence
- 2. Adolescence and Puberty: 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. Puberty :- During adolescence the body undergoes several changes and becomes capable of reproduction. These changes are the beginning of puberty.
- 4. Changes at Puberty An individual goes through different changes during the onset of puberty... It differs in males and females, also the extent of these changes is different in each person. Each individual goes through changes like increase in height, change in body shape, change in voice, development of sex organs, mental, intellectual and emotional maturity Adam's apples develop during puberty and are not present in prepubescent children...
- 5. Boys: 1. The growth of facial hair. 2. The growth of body hair including underarm, abdomen, chest hair and pubic hair. 3. Chest and shoulders widen and body becomes muscular 4. Skin becomes more rough and porous, secretion of sweat glands and sebaceous glands increase 5. Larynx (Adams apple)/voice box protrudes out and voice becomes deep and husk. Girls: 1. Enlargement of breasts,Widening of hips 2. The growth of body hair, prominently in the underarm and pubic areas. 3. Changed fat distribution. More fat below the skin, at hips, buttocks and thighs. 4. Development of secondary reproductive organs.
- 6. Secondary sexual characteristics These are external, visible characteristics that develop in boys and girls after puberty, help to distinguish two sexes and are not directly involved in reproduction. Few of them are as follows.
- 7. Hormones Hormones are chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions. There are many types of hormones that act on different aspects of body functions and processes As we have studied in ch 9 that, male hormones (Testosterone) are releasd by testes and female hormones(estrogen and progesterone) are released by ovaries These hormones make changes in the body initiating reproductive muturity...
- 8. Sex hormones and other hormones Pituitary gland The pituitary gland is situated in the brain and is called as a master endocrine gland. It produces hormones that instruct other glands to secrete their hormones. The pituitary gland secretes growth hormone which controls the overall growth of a person. Secretion of growth hormone is maximum in adolescence period. Testosterone Testosterone is the primary male sex hormone. It is responsible for the development of the male reproductive organs and development of secondary sexual characteristics too. Testes start secreting testosterone only after puberty. Estrogen Estrogen/oestrogen is the primary female sex hormone. It is responsible for the development of the female reproductive organs, production of female gamete i.e. ova and development of secondary sexual characteristics and menstrual cycle.
- 9. Thyroid gland It is a butterfly-shaped gland situated in the throat. It secretes a hormone called thyroxin. This hormone is important as it maintains the balance of all metabolic activities. The deficiency of this hormone can cause swelling of the thyroid gland, leading to goitre. Pancreas The pancreas secretes a hormone called insulin, which regulates the blood sugar level in the body. Deficiency of insulin leads to diabetes. Adrenal glands The adrenal glands are situated right above the kidneys. They change their shape throughout life and shrink as a person grows older. They secrete a hormone adrenaline and also maintain the salt and pH balance. Hormone adrenaline is also called fight or flight hormone as it functions in emergency situations.
- 11. 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. 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.
- 12. 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(23) 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.
- 14. Role of Hormones in completing the Life History of Insects and Frogs. Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by thyroid. Thyroxine production requires the presence of iodine in water.
- 15. Reproductive health Personal hygiene Personal hygiene is very important, especially during teenage. Increased activity of sweat glands sometimes makes the body smelly. It also leads to acne. All parts of the body should be washed and cleaned every day. If cleanliness is not maintained there are chances of catching bacterial and fungal infections. Balanced diet Adolescence also equates to a sudden spurt in growth of the body. A growing body requires all the nutrients. Therefore, all the teenagers should consume a balanced diet and not junk food. A balanced diet is a meal that includes proteins, carbohydrates, fats and vitamins in proper proportions. Junk food affects the growth of an individual.
- 16. Physical exercise Exercise ensures a healthy body and mind. Walking, playing or practising yoga are some of the many ways we can carry out physical exercise. Say NO to Drugs Drugs are addictive and harm the body in long term. Sometimes harm done by drugs becomes irreversible. Any teenager should say NO to drugs. People who are addicted to drugs have more chance of having HIV infection...