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Reaching the age of adolescence class 8

 

Introduction

  • In this chapter, we will learn about the changes that take place in the human body by which a person becomes capable of reproduction.
  • Here, we shall discuss the role that hormones play in bringing about changes that make a child grow into an adult

Adolescence and Puberty

  • Growth begins from the day one is born. But upon crossing the age of 10 or 11, there is a sudden spurt in growth which becomes noticeable. The changes take in the body are part of growing up. This indicate that child are no longer a child but are on the way to becoming on adult. Growing up is a natural process.
  • The period of life, when the body undergoes changes, leading to reproductive maturity, is called adolescence. It begins around the age of 11 and lasts upto 18 or 19 years of age. The adolescents are also called ‘teenagers’. In girls adolescence may begin a year or two years earlier than in boys. Also, the period of adolescence varies from person to person.
  • The human body undergoes several changes during adolescence. These changes mark the onset of puberty. The most important change which marks puberty is that boys and girls become capable of reproduction. Puberty ends when an adolescent reaches reproductive maturity.

 

CHANGES AT PUBERTY

 

Increase in Height

 

  • The most conspicuous change during puberty is the sudden increase in height. All this time the long bones, that is, the bones of the arms and the legs elongate and make a person tall.
  • The girls grow faster than boys by about 18 years of age, both reach their maximum height. The rate of growth in height varies in different individual. The height of an individual (male or female) depends on the genes inherited from parents. However, right kind of food during growing years is also essential.

Calculation for full height (in cm)

  • The average rate of growth in the height of boys and girls with age given in the chart helps in calculating full height of the individuals.

Formula,

For example : A girl is 9 years old and 120 cm tall. At the end of the growth period, she is likely to be × 100 cm = App. 140 cm tall.

Age in years % of full height
Boys Girls
8 72% 77%
9 75% 81%
10 78% 84%
11 81% 88%
12 84% 91%
13 88% 95%
14 92% 98%
15 95% 99%
16 98% 99.5%
17 99% 100%
18 100% 100%

 

Change in Body shape

  • The age of puberty, boys have broader shoulders and wider chests than boys in junior classes. Ingirls, the region below the waist becomes wider.
  • In boys, the muscles of the body grow more prominently than in the girls. Thus, changes in occurring in adolescent boys and girls are different.

Voice Change

  • At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes. The growing voice box in boys can be seen as a protruding part of the throat called adam’s apple.
  • In girls the larynx is hardly visible from the outside because of its small size. Generally, girls have a high pitched voice, whereas boys have a deep voice.

Adam’s apple in a grown up boy

Increased activity of Sweat and Sebaceous gland

  • During puberty the secretion of sweat glands and sebaceous glands (oil glands) increases. Many young people get acne and pimples on the face at this time because of the increased activity of these glands in the skin.

Development of Sex Organs

  • At puberty, male sex organs like the testes and penis develop completely. The testes also begin to produce sperms. In girls the ovaries enlarge and eggs begin to mature. Also ovaries start releasing mature eggs.

Reaching Mental, Intellectual and Emotional Maturity

  • Adolescence is also a period of change in a person’s way of thinking. Adolescents are more dependent than before and are also self conscious.
  • Intellectual development takes place and they tend to spend considerable time thinking. In fact, it is often the time in one’s life when the brain has the greatest capacity for learning. An adolescent may feel insecure while trying to adjust to changes in the body and mind.

Secondary Sexual Characters

  • Such as development of breasts in girls, moustaches and beard in boys, begin to develop. These characters that help in distinguishing the males from the females are called secondary sexual characters. Boys also develop hair on their chest.

Hormones 

  • Hormones are chemical substances secreted in endocrine glands. They are also known as ductless glands. These glands release hormones directly to the blood stream to reach a particular body part known as target site.
  • Hormones control the changes that occur at adolescence. The male hormone called testosterone is secreted by the testes at the onset of puberty In girls, ovaries secrete female hormone or oestrogen which makes the breast develop. Their secretion is regulate by the pituitary endocrine gland.

Reproductive Phase of Life in Humans

  • Adolescents become capable of reproduction when their testes and ovaries begin to produce gametes. The capacity for maturation and production of gametes lasts for a much longer time in males than in females.

 

Menstruation

  • The uterine wall in females prepares itself to receive the developing fertilized egg. In case there is no fertilization, the thickened lining of the uterine wall breaks down and goes out alongwith blood. This bleeding in women is called menstruation which occurs once in about 28 to 30 days. Initially, menstrual cycle may be irregular. It take some time to become regular.
  • Menarche :The first menstrual flow which begins at puberty is known as menarche.
  • Menopause : At 45 to 50 years of age, the menstruation cycle stops. Stoppage of menstruation is known as menopause.

 

How is the sex of the baby determined?

 

  • The fertilized egg or zygote is the instruction for determining the sex of the baby. This instruction is present in the thread-like structures called chromosomes in the fertilized egg. The chromosomes are present inside the nucleus of every cell. All human beings have 23 pairs of chromosomes in the nuclei of their cells. Two chromosomes out of these are the sex chromosomes named X and Y. A female has two X chromosomes, while a male has one X and one Y chromosomes. The gametes (egg and sperm) have only one set of chromosomes. The unfertilized egg always has one X chromosomes. But sperms are of two kinds. One kind has as X chromosome, and the other kind has a Y chromosome.
  • When a sperm containing X chromosome fertilizes the egg, the zygote would have two chromosome and develop into a female child. If the sperm contributes a Y chromosome to the egg (ovum) at fertilization, the zygote would develop into a male child.
  • The sex chromosomes of the father determine the sex of an unborn baby. They belief that the mother is responsible for the sex of her baby is completely wrong and to blame her for this is totally unjustified.

Sex determination in humans

Role of Hormones in Completing the Life History of Insects and Frogs

  • In the life history of the silk, the caterpillar has to pass through various stages to become an adult moth. Similarly, the tadpole passes through certain stages to become a frog.
  • The changes from larva to adult is called metamorphosis. Metamorphosis in insects is controlled by insect hormones. In a frog, it is controlled by thyroxine, the hormone produced by thyroid.
  • Thyroxine production requires the presence of iodine in water. If the water in which the tadpoles are growing does not contain sufficient iodine, the tadpoles cannot become adults.

Reproductive Health

  • The physical and mental well being of an individual is regarded as an individual’s health. To keep the body healthy, every human being at any age, needs to have a balanced diet. The person must also observe personal hygiene and undertake adequate physical exercise.

Nutritional Needs of the Adolescents

  • Adolescence is a stage of rapid growth development. Hence the diet for an adolescent should be a balanced diet.
  • “A balanced diet means that the meals include proteins, carbohydrates, fats and vitamins in requisite proportions”.
  • Our Indian meal as roti/rice, dal (pulses) and vegetables is a balanced meal. Milk is a balanced food in itself. Fruits also provide nourishment. For infants, mother’s milk provides all the nourishment that they need.

Nutritious Items of Foods

  • Iron builds blood and iron-rich food such as leafy vegetables, Jaggery (Gudd), meat, citrus, Indian gooseberry (amla) are good for adolescents.
  • Chips and packed or tinned snacks, through very tasty should never replace regular meals as they do not have adequate nutritional value.

Personal Hygiene

  • Everyone should have a bath atleast once everyday. It is more necessary for teenagers because the increased activity of sweet glands sometimes makes the body smelly. All parts of th body should be washed and cleaned everyday. If cleanliness is not maintained there are chances of catching bacterial infection.
  • Girls should take special care of cleanliness during the time of menstrual flow.

Physical Exercise

  • Walking and playing in fresh air keeps the body fit and healthy. All young boys and girls should take walks, exercise and play outdoor games.

Say ‘No’ to Drugs

  • Adolescence is a period of much activity in the body and mind which is a normal part of growing up. So do not feel confused or insecure.
  • If anybody suggests that you will get relief, if you take some drugs, just say ‘No’ unless prescribed by the doctor. Drugs are addictive. If you take them once, you feel like taking them again and again. They harm the body in the long run. They ruin health and happiness.
  • The AIDS which is caused by a dangerous virus HIV. This virus can pass on to a normal person from an infected person by sharing the syringes used for injecting drugs.
  • It can also be transmitted to an infant from the infected mother through her milk. The virus can also be transmitted through sexual contact with a person infected with HIV.

 

 

 

 

 

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EXERCISE

 

  1. I) Very Short Answer Type Questions :

 

  1. What do you mean by health?
  2. How can we keep our body healthy?
  3. Name some iron rich food items.
  4. How many types of chromosomes in sperms are there?
  5. What is the name of hormone produced by adrenal glands?
  6. What is the legal age for marriage for girls and boys?
  7. Name the hormone which controls metamorphosis in frog.
  8. Name the hormone which is necessary for the normal growth of a person.
  9. Why does mother’s milk is considered a better diet for infants?
  10. What do you mean by a balanced diet?

 

  1. II) Short Answer Type Questions :
  2. What is adolescence?
  3. Why is adolescence also called teenage?
  4. What is the most important change makes puberty?
  5. What happens when egg is fertilized?
  6. Explain the development of sex organs in male and female.
  7. Why pituitary gland is called master gland?
  8. What happens when egg is fertilized?
  9. A boy is 9 years old and 120 cm tall. Calculate the height of the boy at the end of growth period.
  10. Write the factors which effects the height of a person.
  11. Some boys and girls have improportionate body parts during adolescence. Why?

III) Long Answer Type Questions :

  1. Explain the changes that occur in the voice of boys and girls during puberty?
  2. Explain the terms menstruations, menarche and menopause.
  3. How do hormones help in the completion of life history of insects and frogs?
  4. What is the cause of the changes in human body during puberty?
  5. How do hormones work? Explain with the help of a flow chart?
  6. Explain the sex determination of a baby in human.
  7. What are the endocrine glands? Write the name of hormones and the functions of thyroid, pancreas and adrenal glands.
  8. What do you mean by health? What are the factors which help to keep a good health?
  9. Fill in the blanks

(a)      Voice box is also called ____________________.

          (b)      Initially girls grow _________________ than the boys.

(c)      Testosterone is the ___________ hormone and estrogen is ______________.

(d)      Growth hormone is produced by the ______________ gland.

(e)      There are ___________________ pairs of chromosome in human cell.

  1. Match the item given in Column A with these in Column B suitably.
  Column-A   Column-B
1. Puberty age in females A Sperms
2. X type or Y type of chromosome B 10 to 12 years
3. Male hormone C Diabetes
4. Start age of adolescence D 11 to 18 years
5. Less secretion of insulin E Testosterone

 

 

 

 

 

WORKSHEET-1

  1. What do you mean by ‘Adolescence’?

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  1. When the adolescence age begins in boys and girls?

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  1. Define puberty and how it is related to adolescent?

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  1. What are the changes occurs at puberty age in boys and girls related to their height?

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  1. How you can calculate the full height in boys and girls?

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WORKSHEET-2

  1. What changes are occur in body shape in boys at age of puberty?

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  1. How the voice become changes in age of puberty in boys and girls?

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  1. What change occur in body shape in girls at age of puberty?

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  1. What causes, when increased activity of sweat and sebaceous glands occur at age of puberty?

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  1. What is the most important change occurring in puberty age?

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WORKSHEET-3

  1. What do you mean by secondary sexual characters?

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  1. What are the secondary sexual characters in girls?

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  1. Write some secondary sexual characters in boys.

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  1. What is the cause of the changes in human body during puberty?

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  1. How do hormones work?

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WORKSHEET-4

  1. How do sex hormones work in the human body?

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  1. Explain the term menstruation.

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  1. Differentiate between menarche and menopause.

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  1. How is the sex of the baby determined?

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  1. Name the hormones which are other than sex hormones?

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WORKSHEET-5

  1. What do you mean by health?

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  1. Name the virus that causes AIDS. What are the medium through which this virus is transmitted?

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  1. Draw a diagram of a body which shows position of various endocrine glands.

 

 

 

 

 

 

 

 

 

 

 

  1. What are endocrine glands? Write the names of hormones and the functions of thyroid, pancreas and adrenal glands.

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  1. How do hormones help in the completion of life history of insects and frogs?

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WORKSHEET-6

  1. What do you mean by a ‘balanced duct’?

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  1. What are the factors which help to keep a good health?

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  1. Write a short notes on Adam’s apple.

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  1. Define the term “Hormone”.

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  1. Write the functions of sex hormone like testosterone and oestrogen.

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notes

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