CLASS: VIII NCERT (CBSE)
Biology
Reaching the age of Adolescence
SUMMARY
Changes During Puberty
After the age of ten years, an individual becomes anadolescent, and experiences a lot of physical changes in the body.Adolescent is a general term for teenagers of both sexes.Adolescence is the period of life between the onset of puberty and reaching adulthood, that is, the period that leads to reproductive maturity.An increase in height is the most apparent physical change during puberty.Exercise and eat healthy food to gain height faster.
Everyone will not have the same rate of increase in height, as the height of individuals is controlled by thegenes inherited from parents. During adolescence, thebody shapes of boys and girls also change an increase in their heights. The larynx or voice box in boys grows during puberty and protrudes out, making it clearly visible, and is commonly called Adam’s apple. During puberty, sweat glands become active and start producing more sweat. During puberty, pimples or acneappear due to increased action of sebaceous glands oroil glands.
During puberty, the sex organs grow and become functionally active. The testes start producing male gametes, called sperms. During puberty, the ovariesgrow and result in the maturation of the ovum. There is an increase in size of the penis with respect to different ages in males. Adolescents may experience mood swings during puberty. Puberty also results in mental and intellectual maturity.
During puberty, the brain is very active and so will have a greater capacity to learn. Adolescence is the period of life that leads to reproductive maturity, making a person capable ofreproduction. The growth of facial hair, that is, the beard and moustache, is a secondary sexual characteristic visible during adolescence. Puberty is marked by the development of breasts in girls Secondary sexual characters are used to distinguish a male from a female.
Hormones and Reproductive Function
Hormones are chemical messengers that regulate most functions in the human body. Endocrine glands orductless glands secrete hormones directly into the bloodstream. Sex hormones control the onset ofpuberty and initiate the reproduction function. Body changes such as the growth of facial hair and cracking of voice, are initiated due to the secretion of testosterone. Body changes in females during puberty, such as breast development, are initiated by estrogen.
At puberty, the level of sex hormones is sufficient to bring about the maturation of gametes, sperm and ovum. Thereproductive phase of life lasts longer in males than in females. Menarche is the first occurrence of menstruation. The shedding of the uterine thickening along with its blood vessels is menstruation.
Menopause is the stoppage of menstruation.Fertilisation is the fusion of a sperm and an ovum.
The menstrual cycle takes place every 28-30 days. Sex chromosomes in sperms determine the baby’s gender. Humans have 23 pairs of chromosomes in each cell.
A gamete is a mature reproductive cell – a sperm or an ovum. Gender determination of an unborn baby is considered illegal in India. Goitre is caused by the enlargement of the thyroid gland. Insulin deficiency causes diabetes. The thyroid gland produces thyroxine and calcitonin. The adrenal glands secrete adrenalin.
The pituitary gland is the master gland and controls all the endocrine glands. The life cycle of the silk moth is controlled by insect hormones. Thyroxine is responsible for metamorphosis of the larva or tadpoles into adultfrogs.
Adolescence-and-Health
Adolescents need to avoid junk food. A balanced dietcontains nutrients like carbohydrates, proteins, fats, vitamins, minerals and water in the right proportions.Healthy foods have more nutritional value, whereas junk foods have no or little nutritional value.
A person with complete physical and mental health is termed a healthy individual. Personal hygiene is the first step in maintaining health. Cleanliness – Cleaning of private parts is important to prevent possible infections. Many myths and taboos about menstruation and pregnancy prevail in society. Body parts such as hair, skin, nails and feet are vulnerable to bacterial andfungal infections, if we don’t keep them clean. The activity of sweat glands increases in puberty and makes the body smell. Physical exercise keeps your body fit and healthy. Sweating helps you to release toxins and wastes from your body.
Outdoor games and exercise in addition to indoor games will help you build a healthy, muscular body. A lot of people take anabolic steroids to increase body mass, but it has dangerous side effects. Peer pressure is best addressed by self confidence and a healthy lifestyle. During adolescence, with drastic changes taking place in the body and mind, you might feel insecure and confused. Drugs are addictive and should only be taken under prescription of a physician.
AIDS is caused by a virus called HIV. AIDS can be transmitted from an infected person to a healthy person by sharing syringesused for injecting drugs. Pregnancy occurs only bysexual contact. In India, the legal age for marriage is 21 years for a boy and 18 years for a girl.
