DIFFERENT STAGES OF LIFE AND ROLE OF HORMONES:
The human beings can reproduce only after a certain age because their reproductive systems start working only after a certain age. It is the hormones which bring about changes that make a child grow into an adult.
1. A young human being below the age of full physical development is called a child.
2. A mature human being who is fully grown and developed is called an adult.
3. The transitional period of physical and mental development which occurs between childhood and adulthood is called adolescence.
4. The period of life of a person when the body undergoes a lot of changes leading to reproductive maturity is called adolescence.
5. A person who is in the process of growing from a child to an adult is called an adolescent. Adolescence is usually begins around the age of 10 or 11 and lasts up to 18 or 19 years. They are also known as teenagers.
6. Adolescence is the time between childhood and adulthood.
7. Puberty is the time when adolescent become sexually mature. The period during which adolescent boys and girls reach sexual maturity and become capable of reproduction is called puberty.
8. Puberty tends to start earlier in girls than in boys. Girls attained puberty at a lower age of 10 to 13 years, while boys reach puberty at a comparatively higher age of 12 to 14 years.
9. During the puberty development of secondary sexual characteristics occur in both boys and girls.
10. All the changes which occur in boys and girls at puberty are brought about by various hormones.
11. The most conspicuous change during puberty is the sudden increase in the height of of boys and girls.
12. The height of a person depends on the genes inherited from the parents.
13. When puberty sets in, a time of rapid changes in body shape and appearance starts in boys and girls which make the boys and girls look different from one another.
14. Some of the changes in body shape and appearance in boys and girls brought about by the onset of puberty are as follows:
a. Boys develop broader shoulders and wider chests than girls.
b. Girls develop broader hips than boys. Due to this, the region below the waist becomes wider in girls.
c. Boys develop more muscle than girls. So, the body of boys looks more muscular than that of girls.
d. Girls develop breasts. This also changes the body shape of grown up girls and makes them look different from boys.
e. Boys develop Adam's Apple which makes them look different from girls.
f. Boys develop facial hair like moustache and beard, girls do not have facial hair. Growth of facial hair makes boys look different from girls.
15. Changes at puberty:
a. Increasing height:
When puberty sets in there is a rapid increasing height of boys and girls. Initially girls grow faster than boys. The rate of growth in height varies in different persons.
Full height of a person = (present height of a person/percentage of full height at present age) x 100
Solution: present height of the boy = 125 cm
Percentage of full height = 75%
So, full height of the boy = (125/75) x 100 cm
= 166.67 cm
b. Change in body shape and appearance
a. Boys develop broader shoulders and wider chests than girls.
b. Girls develop broader hips than boys. Due to this, the region below the waist becomes wider in girls.
c. Boys develop more muscle than girls. So, the body of boys looks more muscular than that of girls.
d. Girls develop breasts. This also changes the body shape of grown up girls and makes them look different from boys.
e. Boys develop Adam's Apple which makes them look different from girls.
f. Boys develop facial hair like moustache and beard, girls do not have facial hair. Growth of facial hair makes boys look different from girls.
c. Change in voice
The growth of voice box in boys is much more than the growth of voice box in girls. The bigger boys box in boys gives deeper voice to the boys. The bulge or projection the front of throat or neck in grown up boys is called Adam's Apple. The smaller voice box in girls gives shrill voice or high pitched voice to the girls.
d. Development of pimples and acne on the face.
Pimples are small red spots on the face of a person. Acne is a skin condition marked by the eruption of numerous red pimples on the face. The pimples and acne are formed due to the increased activity of of sebaceous glands and sweat glands present in the skin.
e. Development of sex organs
The testes begin to produce male sex cells called sperms at puberty. The ovaries start releasing mature eggs or ova at puberty.
f. Reaching mental, intellectual, and emotional maturity.
Adolescence is a period which brings maturity is a person's way of thinking.
The changes which take place in body and mind during adolescence are a natural part of the growing up process. Every human being has to pass through this stage.
Adolescence is a period which also brings intellectual maturity. Adolescence is the time in one's life when the brain has the greatest capacity for learning.
16. HORMONES:
Hormones are the chemical substances whitch co-ordinate the activities of living organisms and also their growth.
The hormones involved in the development and control of the reproductive organs and secondary sexual characteristics are called sex hormones.
The male sex hormone is known as testosterone and female sex hormone is known as oestrogen.
17. Exocrine glands and endocrine glands
A gland is a structure which secretes a specific substance or substances in the body. A gland which secretes is product into a duct or tube is called and exocrine gland. For example, salivary glands secrets is product into a duct called salivary duct. Sweat glands and sebaceous glands are also exocrine glands.
A gland which does not have a duct and secrets is product directly into the bloodstream is called an endocrine gland. An endocrine gland makes a chemical substance called hormone. Pituitary gland, thyroid gland, adrenal glands are example of endocrine gland.
17: SEX HORMONES:
The onset of puberty is controlled by hormones. The testes make male sex hormone called testosterone and ovaries make female sex hormone called oestrogen. The production of sex hormone is controlled by pituitary gland.
18. FUNCTIONS OF OF TESTOSTERONE AND OESTROGEN:
Testosterone: Testosterone hormone performs the following functions:
a. Testosterone hormone produces male secondary sexual characteristics in boys at puberty.
b. Testosterone hormone causes the growth and development of male sex organs at puberty.
c. Testosterone hormone causes growth spurt in boys at puberty.
Oestrogen: Oestrogen hormone perform the following functions.
a. Oestrogen hormone produces female secondary sexual characteristics in girls at puberty.
b. Oestrogen hormone causes the growth and development of female sex organs at puberty.
c. Oestrogen hormone brings about the monthly preparation of uterus for pregnancy.
19. Menstrual cycle:
In females the reproductive phase of life begins at puberty at the age of 10 to 12 years and generally lasts till the age of approximately 45 to 50 years.
PREGNANCY:
With the onset of puberty, the eggs begin to mature in the ovaries of a woman. One mature egg is released by one of the over is of the women once in about 28 to 30 days. During this period, the inner lining of uterus grows and becomes thick and spongy, and prepares itself to receive the fertilized egg. So, in case the fertilization of egg cell occurs by a sperm, the fertilized Excel begins to divide to form an embryo. The embryo then gets embedded in the thick uterus lining. This results in pregnancy.
MENSTRUATION:
If fertilization does not occur, then the egg released by the ovary dies within a few days and the thick lining breaks down. Since the thick uterus lining contains a lot of blood vessels therefore the breaking down of uterus lining produces blood along with other tissues. This blood and the other tissues come out of vagina of women in the form of a bleeding.
The bleeding from the uterus which occurs in a woman every month is called menstrual flow or menstruation. Menstruation occurs once in in about 28 to 30 days.
The first occurrence of menstruation activity is called Menarche.
The permanent stoppage of menstruation in a woman is called menopause.
The process of ovulation and menstruation in women is called menstrual cycle and it is controlled by hormones.
20. The two chromosomes that determine the sex of an offspring are called sex chromosomes. The two sex chromosomes are named X chromosome and Y chromosome. The baby develops from XX combination of sex chromosomes in zygote is called a girl. The baby develops from XY combination of sex chromosome in zygote is a boy. It is the sperm of man which determines the sex of the child. The egg cells of woman cannot decide the sex of the child because all the egg cells contain the same sex chromosome, X chromosome.
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