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Reaching the age of Adolescence - Class 8 : Notes

Adolescence: Adolescence is that period of life when many changes start taking place in the body; which results in reproductive maturity. It usually begins at around age of 10 years and is seen till 18 or 19 years of age.
Adolescents are also called as teenagers as teen age period is also covered up in adolescence.
Teenage: The number of years during adolescence span is counted as ‘teen’, .e.g. thirteen, fourteen and fifteen. Hence, this duration is also termed as teenage.

Puberty: The process of transformations taking place during adolescence period is known as puberty. The onset of puberty points out the starting of adolescence. And the end of adolescence or puberty informs about the completion of reproductive maturity.

The Various Changes taking place during puberty
1. Increase in Height:

(i) It is the most visible change noticed during the puberty.
(ii) In the beginning, it is observed that the girls grow faster than boys, but, on reaching 18 years of age, both gain their maximum height. Also, the rate of growth in height differs individually.
(iii) During these years, it is really significant to eat nutritious food for better development of bones, muscles and other parts of the body.

2. Change in Body Shape:
(i) During puberty, boys will start having broad shoulders and wider chests while in case of girls the region below the waist becomes broader.
(ii) Moreover, the muscles of boys will grow more prominently than in the girls.

3. Change in Voice
(i) During puberty, it is being noticed that voice of boys starts cracking and their voice box or larynx starts to grow.
(ii) Adam’s apple: The increase in the size of voice box in boys is seen as a prominent protrusion in the neck. This protrusion is called Adam’s apple.

Adam’s apple

Moreover, girls will usually have a high pitched voice while the boys will have deeper voice.

4. Increased Activity of Sweat and Sebaceous Glands:
The Sweat glands present starts operating and produces more sweat. And the Sebaceous glands or oil glands increased function results in pimples or acne.


5. Development of Sex Organs:
(i) Growth of sex organs takes place and are found to be more active. In males, the testes start to produce male gametes, called sperms. And in females, the ovaries start developing and releases one mature ovum once in 28 days.
(ii) In males, the size of the penis increases with respect to ages. On the other hand, development of breasts is observed in females.

6. Reaching Mental, Intellectual and Emotional Maturity:
(i) Brain becomes more active and so more learning take place.
(ii) Mental and intellectual maturity is seen.


Secondary Sexual Characters: These are the characters that distinguish a male from a female.
1. In males, growth of hair is seen on face and body. And hair growth is seen in the under the arms and in the region above the thighs or pubic region in females.
2. Shoulders get broad and chest gets widened in males. The waist gets wide and hips get narrow in females.
3. The development of breasts takes place in females.
4. Mood swings are seen in males as well as females. Mental and emotional maturity is attained by both sexes. Brain gets more active and has capability of learning more.

Hormones are the chemical substances secreted by endocrine glands for proper functioning taking place during adolescence in the human body
In males, at the beginning of puberty, the hormone or testosterone begins to get released by the testes. And this results in some changes in boys like the growth of facial hair, deep voice and hair on chest.
In females, ovaries start to produce the female hormone or estrogen which results in breasts development on reaching puberty. Also, milk secreting glands or mammary glands development takes place inside the breasts.

The production of these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.  The testes and ovaries secrete sex hormones. These sex hormones are controlled by the hormones secreted from the pituitary gland. The pituitary secretes many hormones, one of which makes ova mature in the ovaries and sperms form in the testes.

The onset of puberty is controlled by hormones

Humans Reproductive Phase:
The reproductive stage starts with the beginning of puberty and it is observed in boys and girls at near about same age. But, reproductive phase in males remain much longer in comparison with females. In women, the reproductive phase starts at puberty (10 to 12 years of age) and lasts till about 50 years of age. While in males, the reproductive phase lasts even above 60 years of age.

In females, each month one egg is set free by either of the ovaries. The uterus forms a thickening to support a foetus to keep it ready in case of pregnancy. If fertilization of egg does not take place, then egg and thickening in uterus are removed in small parts. As a result, bleeding in the vagina takes place for some days. This bleeding through vagina at the end of menstrual cycle, is known as menstruation.
The sequence of events starting from the release of an egg and till egg gets removed is called menstrual cycle. A menstrual cycle normally comprise of 28 to 30 days.

Menarche: It is the first menstrual bleeding in a girl’s life. And it indicates the beginning of puberty in a girl.

Menopause: It is the ending of menstrual cycle. And it is observed at around 45 – 50 years of age. Menopause indicates the end of reproductive phase.

Hormones Other Than Sex Hormones: 
Sex hormones are not the only hormones responsible for changes during adolescence. There are few other hormones that act in the background.

Position of Endocrine Glands in the Human body

1. Thyroxine: It is released by the thyroid  glands and is present in the front part of the neck. In case of improper secretion of thyroxine, it leads to swelling of the throat, a disease called goitre.

Goitre Disease

2. Insulin: It is hormone, which is  responsible for controlling the sugar level in our body. And this hormone is secreted by the pancreas. If insulin is not secreted properly, then blood sugar level might increase and can result into a condition called diabetes.

3. Adrenaline: It is released from a pair of adrenal glands at the top of kidneys. Adrenaline is called as "fight-flight hormone". It is the hormone of emergency. It also helps in balancing the salt level in the blood.


Sex Determination

Will it be a Boy or Girl?
Gender of a child is dependent on the combination of chromosomes taking place in the zygote. In human beings, normally a cell has 46 chromosomes, i.e. 23 pairs of chromosomes. Out of these 46 chromosomes, 22 pairs are identical. But chromosomes in the 23rd pair may be same or different.
There are two kinds of chromosomes in 23rd pair. They are known as X and Y chromosomes. The last pair (i.e. 23rd) in a male has XY combination, while in case of female it has XX combination.
1. Birth of girl will take place when a sperm with X chromosome fertilizes the egg.
2. Birth of boy will take place when a sperm with Y chromosome fertilizes the egg.

Sex Determination

Role of Hormones in Completing the Life History of Insects and Frogs:
The life span of insects can be categorized into four stages: Egg, Larva, Pupa and Adult.
Metamorphosis: It is the change of insect from larva to an adult.
Hormones in insects control the metamorphosis under the action of thyroxine hormone produced by thyroid.

Reproductive Health:

1. Balanced Diet: During adolescence there is need of proper balanced diet. Proper amount of carbohydrates, protein, fat, vitamins and minerals must be included in food.

Balanced Diet

2. Personal Hygiene: Many physical and psychological changes are observed during adolescence. If good hygiene is not undertaken, it may result into skin diseases. And Girls need special attention during menstrual period.

3. Physical Exercise: Physical exercise not only helps in making a strong body but also helps in proper energy utilization.

Physical Exercise

4. Say ‘NO’ to Drugs: During teen age, anyone might get affected by the negative energies surrounding him. At such times, falling for drugs can ruin your life.

5. HIV (Human Immunodeficiency Virus):  AIDS (Acquired Immunodeficiency Disease) is caused due to this virus. It is incurable disease as yet no medicine can cure it. It might spread due to sexual contact, because of infected needles and from an infected mother to her unborn child. . Hence, prevention is the only way to keep away from this dangerous disease.







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