Science Chapter 10 Reaching The Age Of Adolescence

Hormones.

Adolescence is the period of life, when the body undergoes changes, leading to reproductive maturity. It begins around the age of 11 and lasts upto 18 or 19 years of age. In girls adolescence may begin one or two year earlier than boys.

Menstruation is the bleeding in women because of the shedding of the thick lining of the uterus. the walls of the uterus shed when the fertilization does not take place. Menstruation occurs once in about 28 to 30 days.

The changes that take place in the body at age of puberty are:

(i) Increase in height.

(iii) Change in body shape..

(iv) Change in voice.

(v) Incresed activity of sweat and sebaceous gland.

(vi) Development of sex orgnans.

(vii) Development of secondary sexual charater like fascial hair in boys and breasts in females.

(viii) Attaining the mental, intellectual and emotional stability.

Sex hormones are those hormones which affect sexual development or reproduction. They are responsible for development of secondary sexual characters. Testosterone is a male hormone while estrogen is a female hormone. 

B.

proper diet is needed for the rapid growth taking place in their body.

A.

menstruation starts.

B.

chapati, dal, vegetables.

The growing voice box which can be seen as a protruding part of the throat is called Adam's apple. The voice box or larynx starts growing at the time of puberty and becomes enlarged. The adam's apple is visible in boys but is hardly visible in girls. 

Secondary Sexual Characters are the characters which distinguish a boy from a girl. the secondary sexual characters of boys include hair on chest, under the arms, growth of beard and moustaches while secondary sexual character of girls include  development of breasts and growth of hair under the arms and pubic region. These characters are in control of the sex hormones.

The sex of the unborn baby is determined by the sex chromosomes of the father. An egg has two X chromosome while a sperm has a X and a Y chromosome. An egg will always have an X chromosome. Therefore, if the sperm contributes X chromosome then the baby will be a female (XX) and if the sperm contributes the Y chromosome, the baby will be a male (XY). So it is the father, who is responsible for the sex of the baby.

The graph represents the relation between the age and height of both boys and girls.
From the graph we can conclude that :
During puberty, there is a sudden increase in height of both boys and girls. It can be observed that during the age of 4-8 years, girls have less height as compared to boys. However, as soon as girls reach 12- 13 years, their height shows a sudden increase and becomes more than boys. In later years, growth in both sexes becomes stable. 

Adolescence.

13 years to 18 or 19 years.

Puberty.

Two changes in bodies of boys during adolescence are
i. Growth of beard and moustache.
ii. Deepening of voice.

The elongation of the bones of the arms and the legs makes a person tall. 

Puberty results in the growth of the voice box or the larynx. Boys develop larger voice
boxes which can be seen as a protrudung part of the throat, it is called Adam's apple. The voice box is small in girls and is hardly visible

Adam’s Apple.

At puberty the voice of the boys starts deepening and may become hoarse temporarily.

Secondary sexual characters.

Growth of moustaches and beard is a secondary sexual character of boys.

Growth of breasts is the secondary sexual character of females.

Hormones are the chemical substances secreted by endocrine glands.

Testosterone.

Estrogen.

A female has two X chromosomes thus it has XX chromosome composition, while a male has one X and one Y chromosomes making it XY composition

The egg always has one X chromosome.

Sperms has either X chromosome or Y chromosome.

The sex chromosomes of father determines the sex of the baby.

Legal age for marriage is 18 years for girls and 21 years for boys.

Adolescence is called teens because it covers 13 to 18 or 19 years of age. 

Menarche.

Menopause.

X and Y.

Y Chromosome determines the sex of the individual. The presence of Y chromosome forms a male (XY) while the absence of it indicates a female (XX).

Thyroxine.

Insulin.

Endocrine glans are referred to as ductless glands because they release the hormones directly into the blood stream. They do not have any ducts for their secretion. 

Pituitary gland is attached to brain.

Thyroxine hormone controls metamorphosis in frogs.
Insect hormones control insect metamorphosis.

(i) In boys - During adloescence the shoulders become broader and chest becomes wider. The muscles of the body grows more prominent. 

(ii) In girls -  The region below the waist becomes wider during adolescence.

Adolescence is marked by growing of moustache and beard in boys, development of breasts in girls, start of mentruation in girls, sudden increase in height, change in voice  and growth and maturity of reproductive organs. 

During puberty the long bones, that is, the bones of the arms and the legs elongate making a person tall. The lengthening of the bone results in the gain in height. 

Some boys and girls have disproportionate body parts during adolescence because of the different growth rate of different body parts. The growth rate of arms and legs is higher than the other parts. The other parts soon catch up resulting in a proportionate body.

Many changes take place in the bodies of boys and girls during adolescence. Their shoulders become wider and chest becomes broader. Girls get developed breasts and their hips become wider. Muscles of boys grow more than the girls.

The voice box or the larynx begins to grow during puberty. The growth is more in the boys and the larynx can be seen as the protruding part of th throat. The protruding part is known as the Adam's apple. The voice of the boys becomes deep. In boys the voice becomes hoarse temporarily because of the out of control growth of muscles of the voice box. The voice box is growth is less in girls and they have a high pitched voice.

The acne and pimples are due to the increased activity of the sebaceous or oil glands during puberty. During adolescence the sweat glands and oil glands become more active. The sebacious glands secrete more oil resulting in the growth of acne and pimples.

The sex organs becomes fully developed during puberty. In boys the testes and penis become completely developed and start secreting sex hormone testosterone. The testes starts producing sperms. Similarly in females ovaries get enlarged and secrete estrogen and produce matured eggs. Thus they attain sexual maturity.

The special characters which distinguish a male from a female are called secondary sexual characters. Characters such as beards, moustaches in boys and development of breasts in females etc. are called secondary sexual characters.

General growth refers to different types of developmental process in the body such as increase in height, weight gain, changes in shape and size of body.

Sexual maturation refers to specific changes seen at puberty like development of breast in female, menstruation, growth of moustache and beard in boys, deepening of the voices in the boys, growth and maturity of sex organs etc.

The changes which occur during puberty are caused due to hormones secreted by the glands. 

Sex hormones are responsible for the dvelopment of secondary sexual characters. The male sex hormone testosterone is secreted by testes and it causes growth of moustaches and beard. The female hormone estrogen causes the development of breasts and mammary glands.

Pituitary gland is called the master gland. It controls the secretion of the sex hormones. The pituitary also secretes other hormones which help in the maturation of ova in the ovaries and formation of sperm in the testes.The pituitary stimulates the testes and ovaries to produce sex hormones i.e. testosterone and estrogen. The sex hormones initiates the changes that occur in puberty in humans. 

Monthly bleeding in women is called menstruation, If the egg is not fertilized, the released egg and the thick linin of uterus is shed off along with the blood vessels. It is discharged from the body as blood.

The production of thyroxine requires the presence of iodine in water. If iodine is not preent insufficient amount in water. thyroxine is not secreted in the frogs. Since thyroxine is required for metamorphosis, inadequate amount of thyroxine hampers metamorphosis. Thus, the tadpole cannot trasform into adult frogs require thyroxin for the process of metamorphosis. 

Adolescence marks the stage of rapid growth in body. The nutritional requirement of the body increases. Thus, the adolescents need balanced diet containing proteins, carbohydrates, fats and vitamins in requisite proportions. Besides this the adolescent should have fruits too, as fruits are a great source of nourishment. 

If the intake of iodine is low the followinf things may happen:

(a) Since, iodine is requires for the release of thyroxin from thyroid gland, less iodine will result in less thyroxine, thus affecting carbohydrate and fat metabolism.

(b) A person might suffer from goitre because of lack of thyroxine. 

Adolescence leads to mental, intellectual and emotional maturity.  Adolescents become self-conscious and spend more time in thinking. It is the time when our brain has the greatest capacity for learning. Thus, the all round maturity makes them more independent.

(a) Oestrogen

(b) Growth hormone

(c) Insulin

(d) Thyroxine

(a) Pituitary

(b) Pancreas

(c) Adrenal

(d) Testes

(a) (i) Menstruation, (ii) Periods.

(b) Puberty.

(c) The onset of the process indicates that the female has attained reproductive maturity.

(d) Pregnancy.

(e) Menopause.

Various changes occur in the body of human during puberty. These changes occur due to hormones secreted by reproductive organs. These changes are the following :

(a) increase in height : During puberty there is sudden increase in height. 

(b) Change in body shape. The body shape changes during puberty. Boys develop broader shoulders whereas in the girls the region below the waist becomes wider.

(c) Hyperactive sebaceous and sweat glands- Puberty increases the secretions from sweat and oil glands. May also cause pimples and acnes in some young people.

(d) Change in Voice : The voice box enlarges. Deeping of voice takes place in boys while girls voice becomes high pitched. 

(e) Development of Sex Organs : The reproductive organs of boys and girls become mature. Testes start producing sperms and ovaries release matured eggs.

(f) Mental and Emotional Maturity : Young people become more mature mentally, emotionally and intellectually.

Following measures can help the young people to maintain their reproductive health.

(a) Balanced Diet : A balanced diet is very important for a growing body. Diet should contain all the necessary elements in required proportion. Elements like carbohydrates, proteins, fats and vitamins should be integral part of a balanced diet. 

(b) Personal Hygiene : One shouldmaintain hygiene. All parts of the body should be washed properly so that no infections can take place .

(c) Physical Exercise : Daily routine of physical exercise keeps the body fit and maintains the circulation of blood. Therefore one should practice exercise regularly. 

(a) Thyroxin controls metamorphosis in insects.

(b) Insulin—regulates blood sugar.

(c) Adrenalin—increases heart rate and supply of blood to various organs.

(d) Growth hormone—regulates growth and development.

(e) Testosterone—controls the secondary sexual charaters in male. 

puberty

13 years

18–19 years

estrogen

hormones

ductless

thyroxine

iodine

milk

XX

pituitary

A.

Voice box

B.

Female gamete

C.

Thyroid gland

B.

18-19 years

D.

All the above

C.

Testosterone

B.

Pituitary

A.

Estrogen

D.

Adrenal

D.

Ovulation

(i)



(ii) Ovary produces estrogen and testes produces testosterone hormone.

(iii) Egg is produced by ovary and sperm is produced by testes.