Class 8 Reaching the Age of Adolescence Notes

Adolescence :-

The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence.

Adolescence begins around the age of 11 and lasts upto 18 or 19 years of age.
Since this period covers the ‘teens’ (13 to18 or 19 years of age), adolescentsare also called ‘teenagers’.

Puberty :-

The time period in which the body undergoes certain changes in their body and reproductive organs to lead sexual maturity is known as puberty.

The most important change which marks puberty is that boys and girls become capable of reproduction.
Puberty ends when an adolescent reaches reproductive maturity

Changes at Puberty :-

Increase in Height
Change in Body Shape
Change in Voice
Development of Sex Organs
Increased Activity of Sweat and Sebaceous Gland
Reaching Mental and Emotional Maturity

Changes in Boys at Puberty :-

Growth of thinner hair on legs and arms.
Broadening of shoulders.
Cracking of voice box.
Skin frequently becomes oily.
Penis occasionally begins to become enlarged and erect.

Changes in Girls at Puberty :-

Growth of thinner hair on legs and arms.
Broadening of hips and thighs.
Skin frequently becomes oily.
Increase in the size of breast and darkening of skin and nipples at the tips of breast.
Girls begin to menstruate.

Adam’s Apple :-

The growing voice box in boys can be seen as a protruding part of the throat called Adam’s apple.

Secondary Sexual Characters :-

The feature help to distinguish the male from the female, they are called secondary sexual characters.

Hormones :-

Hormones are chemical substances which control changes occur in the body at adolescence.

Male Sex Hormone :- Testosterone.
Female Sex Hormone :- Estrogen.

Pituitary Gland :-

The production of these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.

It secrets Growth Hormone.

Target site :-

Endocrine glands release hormones into the bloodstream to reach a particular body part called target site.

Mensuration :-

If fertilisation does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation.

Menstruation occurs once in about 28 to 30 days.

Menarche :-

The first menstrual flow begin at puberty is termed as menarche.

Menopause :-

At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is termed menopause.

Chromosomes :-

The thread like structure present in zygote which carry information for determining the sex of the baby is called chromosomes.

All human beings have 23 pair of chromosomes in their nuclei of their cells.
Two chromosomes out of these are sex chromosomes i.e., X and Y.
A female has two X chromosomes, while a male has a X and a Y chromosomes.

Metamorphosis :-

The change of larva to an adult is known as metamorphosis.

Metamorphosis in insects is controlled by insect hormones.
In a frog, it is controlled by thyroxine. Thyroxine is secrets from thyroid gland.

Balanced Diet :-

A diet consisting of a variety of different types of food and providing adequate amounts of the nutrients necessary for good health is known as Balanced diet.

Class 8

Class 8 Reaching the Age of Adolescence Notes