Reaching the Age of Adolescence CBSE Class 8 Important Notes

What is Adolescence or Adolescent Age?
The period of life, when the body undergoes changes, leading to reproductive maturity is called
adolescence. It begins around the age of 11 years and lasts up to 18 or 19 years of age. Adolescents are
also called ‘teenagers’, In girls, adolescence begins a year or two earlier than in boys.
During adolescence, the human body undergoes a number of changed. The testes start to make sperms
and the ovaries start to make eggs. In other words, the reproductive organs become functional. The age
at which reproductive organs become functionally active is called puberty. At puberty, therefore the
boys and girls become capable of reproduction.

 Changes at Puberty
Growth of the body is an important character during puberty. The different parts of the body during
adolescence grow at different rates. Head, hands and feet reach adult size very soon and therefore look
disproportionately larger for some time. The legs grow faster than the torso and then stop, while the
torso continues to grow.
Change in Body Shape
During adolescence, changes in body shape takes place. These changes are different in boys and girls.
(i) The boys develop broader shoulders and wider chest. In girls, the region below the waist
becomes wider.
(ii) Body muscles grow more in boys than in girls.
 Change in Voice
(i) Boys have a deep voice which in some cases even cracks. Voice becomes hoarse. In girls, the
voice is high pitched.
(ii) Voice box or larynx is bigger in boys and can be seen as the protruding part of the throat called
Adam’s apple. In girls, the voice box is smaller and hardly visible from the outside.
 Increase in Activity of Sweat and Oil Glands
During puberty, there is an increased secretion of sweat and oil (sebaceous) glands. It is because of the
increased secretion that many young people get acne and pimples on their faces.
 Development of Sex Organs
Though reproductive organs are present even in infant stage, but they reach maturity and complete
development during puberty. Testes and ovaries also start producing sperms and eggs respectively.
 Development of Secondary Sexual Characters
These characters which develop at the time of attaining sexual maturity and help to distinguish the male
from the female are called secondary sexual characters. Secondary sexual characters are external
characters which are not directly involved in the process of reproduction.

The changes which occur during adolescence are controlled by chemical substances called hormones.
The hormones are produced in special organs celled endocrine glands. There are a number of endocrine
glands in males and females of humans.

Testosterone hormones produced by testis brings about changes in boys and estrogen produced by
ovaries in girls. Testosterone and estrogen are called sex hormones.
The activity of testes and ovaries are under the control of hormones from another gland called the master
gland or pituitary gland. This gland is located at the base of the brain.
* Endocrine glands have no ducts. For this reason, they are also called ductless glands
* The secretions of endocrine glands are poured directly into the blood.
* The hormones are required in extremely small quantities. Increase of decrease in the specific
quantity is harmful of the body. 
 Hormones other than Sex Hormones
Apart from the pituitary, the testes and the ovaries, there are other endocrine glands in the body. Some
of the major ones include thyroid, adrenal and pancreas.

(i) When a person has a very big and bulging throat, he is suffering from goiter, a disease, due to the
deficiency of the hormone thyroxin produced by the thyroid gland, and
(ii) When a person is suffering from sugar problems, it means that his pancreas is not producing
sufficient quantities of insulin hormone.
Similarly there is hormone adrenalin which helps the body to adjust the stress conditions (like when one
is angry or other tension).

what Happens in Case of Insects and Frog?
Many drastic changes take place in the life history of an insect and the frog, during the process of
metamorphosis.
In insects, metamorphosis is controlled by insect hormones. In case of a frog, it is controlled by
thyroxine hormone. Presence of iodine in water is a must for the production of thyroxine. If the water in
which tadpoles are growing does not contain sufficient iodine the transformation of tadpoles into adult
cannot take place. Even in case of humans, iodine is important for the thyroxine hormone. It us for this
reason that the consumption of iodized salt is recommended.
 Reproductive Phase in Humans
The production of gametes starts earlier in females than in males. In females, this phase begins 10 to 12
years of age while in males, it beginning at 13 to 14 years of age. However, the production of gametes
lasts for a much longer time in males than the females.

In females, the reproductive phase generally lasts up to the age of 45 to 50 years. This period from the
onset of puberty to the age of 45-50 years is marked by a specific event repeated almost every month.
During this period, one ovum matures and is released by one of the ovaries once in about 28 days, and
the wall of the uterus becomes thick so as to receive the egg. In case it is fertilized, it starts developing
and results in pregnancy. If fertilization does not occur, the released egg and the lining of the uterus
along with its blood vessels are shed off. As a result, bleeding takes place in women. This loss of blood
is called menstruation. Menstruation occurs once in about 28 days. The first menstrual flow begins at
puberty and is called menarche. Around the age of 45 to 50 years, the menstrual cycle stops. The
permanent stoppage of menstruation is called menopause.

What Determines Sex of the Baby?
In the males, the least pair of chromosomes consists of one X chromosome and another Y chromosome.
In other words, in males sex chromosomes are XY type.
In the females, both the chromosomes of the last pair are same, and these of X chromosomes. So, the sex
chromosomes in females are of XX type.

 Balance Diet
As the body is in a stage of rapid growth during adolescence, nutritional needs are also more. The diet
during this period has to e a balanced diet.
In such a diet, energy-giving (carbohydrates and fats), body-building (proteins) and protective foods
(vitamins and minerals) are present in requisite proportions.

Milk is a balanced food in itself. Minerals like iron and calcium are very important for all of us. Iron is
essential for blood. Green leafy vegetables, jaggery , meat, eggs, lemon and amla are rich iron. Calcium
is required for bones and teeth. Rich source of calcium are milk, cheese, green leafy vegetables like
spinach, pulses, meat and eggs.
 Personal Hygiene
The basic aim of maintaining personal hygiene is to keep the bacteria and other harmful microorganisms
away from entering the body or infecting the food consumed by us. Otherwise, diseases can
develop.
Following precautions need to be taken for maintaining personal hygiene:
(1) Before and after taking meals, always wash your hands with sap water.
(2) Clean your teeth after each mean and before going to bed. Otherwise tooth decay may take place
(3) Take bath regularly with clean water.
(4) Do not grow long nails. Keep them short and clean
(5) The feet should be cleaned and well protected. Injuries due to bacterial like tetanus, hookworms
and insects may be caused if barefoot walk is undertaken. Walking barefoot must be avoided.
(6) Hairs should be cleaned regularly with soap and water. Combining removes the dirt sticking to
hair.
(7) Eyes should be washed daily with clean and cold water. Rubbing of eyes with hands should be
avoided to prevent the entry of germs into the eyes.
The waste food material and garbage should be disposed off properly. It should not be thrown in the
open. Covered bins must be employed.
v Adequate Exercise, Rest and Sleep
(1) Live a disciplined life
(2) Keep yourself away from tension, long hours of television viewing and long hours of continuous
table work.
(3) Take rest and regular sleep.
(4) Undertake exercise regularly. Brisk walking, running, cycling and swimming are some good
exercise. Exercises help in improving blood circulation. They also help in keeping our longs, heart
and body muscles healthy.
Exercise also helps in resisting infections and building up health.
v Staying away from Alcohol
v Say ‘No’ to Drugs

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