adolescence

Ans1. The sexual cycle in females is called menstrual cycle.

1. On reaching puberty, the hormone oestrogen causes

either of the ovaries to release an ovum into the fallopian

tube once in almost 28 to 30 days. The release of ovum from

the ovary is called ovulation.

2. During this period the inner wall of the uterus becomes

thick, spongy & full of tiny blood vessels and prepares itself

to receive the zygote. In case the matured egg gets fertilised

by the sperm in the fallopian tube, the zygote divides and

redivides to form an embryo which gets embedded in the

uterus lining. This results in pregnancy.

3. If the ovum is not fertilised, then the thick, soft inner lining

of the uterus is not needed and hence it breaks. So, the thick,

soft inner lining of uterus along with the blood and the dead

ovum comes out of the vagina in the form of bleeding called

menstruation. Menstruation usually occurs 14 days after

ovulation and usually lasts for 3 to 5 days.

4. When menstruation is over, the inner lining of the uterus

starts building up again so that it may become ready to

receive the next ovum. Menstrual cycle occurs in women

after about 28 to 30 days (till the time ovum gets fertilised).

Q2. What is the difference between menarche and

menopause ?

Ans2. The first menstrual flow which begins at puberty in

women is called menarche. This marks the begining of

reproductive life of female. The stoppage of menstrual flow at

the age between 45 to 50 years in females is called

menopause.

Q2. List the changes that take place during puberty in

boys and girls.

Ans3. The rapid changes which occur in adolescence due to

hormones secreted by the body are :

1. Increase in height - During puberty there is a sudden

increase in the height of boys and girls due to the increase in

the length of the bones of arms and legs along with the

internal body organs. The height of an individual depends on

inheritance and nutrition.

2. Changes in body shape - are different for boys and girls.

In boys, shoulders become broader and the chest becomes

wider. The body muscles grow more prominently than in the

girls. In girls, hips gain weight and the pelvic region becomes

wider. The development of breasts also begins during this

period.

3. Change in voice - At puberty, the voice box (larynx) begins

to grow.Boys develop larger voice boxes. The growing voice

box can be seen from outside as protruding part of the throat

called Adam's apple. In girls, the voice box is small so is

hardly visible from outside. Generally, girls have high-pitched

while boys have a low-pitched (deep) voice.

4. Increased activity of sweat and sebaceous glands - In

human beings the two important glands in the skin are sweat

glands and sebaceous glands that produce sweat and oil or

sebum, which keeps the skin oily. During puberty, due to the

increased activity of sweat and sebaceous glands, the

secretion of sweat and oil glands increases and the

adolescents get acne and pimples on face. Increased

secretion of sweat in the armpits also results in a

characteristic body odour.

5. Development of sex organs - The male organs like testes

develop completely in boys and start producing sperms. The

female sex organs like ovaries, oviducts and uterus, enlarge

and develop completely in girls. The eggs begin to mature

and the ovaries start releasing eggs.

6. Reaching mental, intellectual and emotional maturity - Many cognitive emotional, intellectual and attitudinal

changes are observed during adolescence. The brain

acquires greatest capacity to learning. The adolescents often

feel confused, have emotional outbursts and frequent mood

swings due to hormonal changes. They become self

conscious and start feeling the need for acceptance and

understanding.

Q3. What is reproductive health ? State the conditions

necessary to maintain good reproductive health during

adolescence.

Ans. The reproductive health of an individual is defined as

his/her physical, social and mental well- being. An

adolescent should follow a healthy lifestyle which includes - 1. Nutritional needs of an adolescent - An adolescent

requires a balanced diet which should contain adequate

amount of all the essential nutrients like carbohydrates, fats,

proteins, vitamins and minerals sufficient for normal growth

and development of the body. A balanced diet helps the

bones, muscles and other body parts get adequate

nourishment required for rapid growth.

2. Personal Hygiene - is essential to prevent infections and

the occurrence of diseases. Increased activity of sweat and

sebaceous glands make the body smell badly. So, the

adolescents should take bath everyday and wear clean

clothes. Girls should take special care of cleanliness during

the time of menstruation.

3. Physical Exercise - keeps the body and mind fit and

healthy. All adolescents should play outdoor games, walk,

run and do yoga for keeping mentally and physically fit.

4. Say 'NO' to Drugs - A positive adolescent must say 'No' to

drugs, alcohol and tobacco because these things cause

many physical and mental diseases.

Q4. How is the sex determined in human beings ?

Explain with the help of a diagram.

Ans. All humans have 23 pairs of chromosomes in the

nucleus of their cells. Out of these 46 chromosomes, 44 are

called autosomes. Autosomes are identical in males and

females. Remaining two chromosomes are called sex

chromosomes. They are represented as X and Y

chromosomes.

In females, the cells contain two identical X chromosomes.

So, the sex chromosomes in females are represented by XX.

In males, the cells contain two different chromosomes X and

Y. So, the sex chromosomes in males are represented by XY.

If the sperm having X chromosome fertilises the egg, the

zygote would have two X chromosomes. It develops into a

female child.

If the sperm carrying Y chromosome fertilises the egg, the

zygote would have one X and one Y chromosome. It

develops into a male child.

So, the sex of a baby totally depends on the father's sperm

and not on the mother's egg.

Q5. Tabulate the location and functions of the following

endocrine glands.

(a) Pituitary (b) Thyroid (c) Pancreas (d) Adrenal

S.No. Endocrine glands

and their location

Hormone

secreted

Main functions and

deficiency diseases

1. Pitutary gland -

located at the base

of the brain

Growth hormone Controls the overall

development or growth of the

body, development of

muscles and bones.

Dwarfism: less secretion

(hyposecretion) of growth

hormone making a person

dwarf.

Gigantism: excessive

(hypersecretion) secretion of

growth hormone making a

person very tall.

2. Thyroid gland- Thyroxine Stimulates the rate of cellular

located in neck

region below larynx

oxidation of carbohydrates,

proteins and fats

Goitre: Iodine is necessary

for the formation of thyroxine.

The deficiency of iodine

produces less thyroxine

causing Goitre.

S.No. Endocrine glands

and their location

Hormone

secreted

Main functions and

deficiency diseases

3. Adrenal gland- a

pair of adrenal gland

is present on top of

each kidney

Adrenaline

Aldosterone

Controls emotions like fear

and anger, regulates blood

pressure and heart beat.

Regulates mineral balance in

the body; hyposecretion

causes Addison's disease.

4. Pancreas- located

below the stomach

Insulin

Glucogon

Lowers the blood sugar level

Diabetes: When pancreas

secrete less insulin, the sugar

level of the blood increases

causing diabetes.

Converts stored glycogon

into glucose, thus increases

the blood sugar level.