Reaching the Age of Adolescence

"Adolescence is the period of life, when the body undergoes changes, leading to reproductive maturity"

1.0Introduction

The human body cannot start reproducing right from birth. It does so only after a certain age. The stage of growth of a baby from birth to about two years of age is called infancy. In this period a baby grows very fast and learns to sit, stand, walk, eat solid food, express its feeling and recognizes people. In childhood (age of two to twelve years), children grow in size and weight. They grow intellectually, emotionally and socially. Children are growing up when the reproductive organs start producing gametes (sperm and ova) and the body becomes capable of reproduction. This stage is known as adulthood. The period of transition from childhood to adulthood during which various biological and psychological changes occur is called adolescence. It is the stage of rapid growth and development which begins around the age of eleven and lasts up to eighteen or nineteen years of age. This period covers the 'teens' (thirteen to eighteen or nineteen years of age), adolescents are called 'teenagers'.

2.0Puberty

The human body undergoes several changes during adolescence, these changes mark the onset of puberty. The age at which sex hormones and gametes begin to be produced and the boy is biologically ready to become a father and the girl is biologically ready to become a mother is called puberty. The rapid growth in adolescence is due to the two hormones, sex hormones and growth hormones. Generally, boys attain puberty at the age of 14 to 15 years while girls reach puberty at the age of 11 to 12 years.

Changes at Puberty: The following changes start taking place in the body of boys and girls at puberty:

1. Increase in height: Initially girls grow faster than boys but by about eighteen years of age, both reach their maximum height. This occurs due to an increase in the length of bones of arms and legs. It is, however, very important to eat the right kind of food during these growing years. This helps the bones, muscles and other parts of the body to get adequate nourishment for growth.

Calculation for full height (as given in the chart) E.g. A boy is 9 years old and 120 cm tall. At the end of the growth period, he is likely to be tall

• The height of an individual is more or less similar to that of some family members. This is because height depends on the genes inherited from parents.

Q. The height of an individual is more or less similar to that of some family members. Why?

• Explanation The height of an individual is more or less similar to parents because height depends on the genes inherited from parents.

2. Change in body shape In boys, shoulders generally broaden as a result of growth. In girls, the region below the waist becomes wider. In boys, the muscles of the body grow more prominently than in the girls.
3. Voice change: At puberty, the voice box or the larynx begins to grow. Boys develop larger voice boxes. The growing voice boxes 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 Boy

Q. Why does voice become hoarse in adolescent boy?

• Explanation In adolescent boys, voice becomes hoarse due to the uncontrolled growth in muscles of voice box but after some time voice becomes normal.

4. 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 their face at this time because of the increased activity of these glands in the skin.

• Reaching mental, intellectual and emotional maturity: Mental growth: Thinking skills develop. They are able to think in a more flexible, abstract, and logical way. The ability to see others point of view, exploring ideas, developing concepts and memory skills improve. Emotional growth: Emotional changes cause the young person to look at friends and family in new ways. They are very happy at one moment and the very next their mood changes. Interest in the opposite sex and desire for closeness arises. Social growth: Developing a personal identity, accepting oneself, forming more mature relationships with peers of both sexes, developing independence and preparing for a career.

1. 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. Ovaries start releasing mature eggs.
2. Secondary sexual characters The features which help to distinguish the male from the female, are called secondary sexual characters. The reproductive organs are testes and ovaries which produce the gametes, sperm in male and ova in female. (i) Secondary sexual characters in male
3. Widening of shoulders
4. Deepening of voice
5. Appearance of beard and moustaches
6. Growth of sex organs (testes and penis) (ii) Secondary sexual characters in female
7. Widening of pelvis and hips
8. High pitch voice
9. Initiation of menstrual cycle
10. Growth of mammary glands (breasts)
11. Maturation of secondary sex organs like fallopian tubes, uterus

Similar secondary sexual characters in male and females are - Growth of hairs in armpits and around pubic area, increased activity of sweat and sebaceous glands, oily skin and appearance of pimples, darkening in skin colour of the genital area.

3.0Endocrine System

All the changes which occur at adolescence are controlled by hormones. Hormones: Hormones are chemical substances which are secreted from endocrine glands or endocrine system.

Endocrine glands: These are ductless glands which secrete their secretions directly into the blood. Some important endocrine glands are as follows -

1. Pituitary gland is located at the base of the brain and secretes growth hormone which is necessary for the normal growth of a person. Hypersecretion of growth hormones causes gigantism while its hyposecretion causes dwarfism.

Pituitary is called master gland because it produces hormones that control other glands. Many glands like thyroid secrete their hormones when they receive orders from the pituitary through its hormones.

1. Thyroid gland is situated in front of the neck below the larynx and secretes thyroxine hormone which regulates the rate of metabolism and also effects the general growth of the body. Hyposecretion of thyroxine hormone results in the formation of swelling in the neck which is called goitre.
2. Pancreas is located below the stomach and secretes insulin hormone which regulates the sugar level in blood. Hyposecretion of insulin hormone leads to diabetes mellitus. Pancreas has both exocrine and endocrine part, so it is also called mixed gland or common gland or heterocrine gland. It secretes hormones like insulin and also secretes digestive enzymes which help in digestion of various components of food.
3. Adrenal glands are located above the kidney and produce the hormone adrenaline. Some hormones secreted by adrenal gland maintain the correct salt and water balance in the blood. Adrenaline regulates the blood pressure and also prepares the body to meet emergencies and to be ready to fight. It helps the body to adjust the stress when someone is very angry, embarrassed or worried.

Q. If the water in which the tadpoles are growing does not contain sufficient iodine. What will happen?

• Explanation The tadpoles cannot become adults because tadpoles change into adults when thyroxine is produced by thyroid gland but in the absence of iodine in water thyroxine is not produced.

1. Ovaries are located in abdomen of female and secrete female hormone or estrogen and progesterone which make the breasts develop. Milk secreting glands or mammary glands develop inside the breasts. The production of these hormones is under the control of another hormone secreted from an endocrine gland called pituitary gland.
2. Testes are located in scrotum of male. Male hormone or testosterone is released by the testes which controls the development of male sexual organs and secondary sexual characters.

Different types of Endocrine glands and their function:

4.0Role of Hormones in Initiating Reproductive Function

Endocrine glands release hormones into the bloodstream to reach a particular body part called target site. The target site responds to the hormone.

The male hormone or testosterone begins to be released by the testes at the onset of puberty. This causes changes in boys, for example, the growth of facial hair. Once puberty is reached in girls, ovaries begin to produce the female hormone or estrogen which helps to develop the breasts. Milk secreting glands or mammary glands develop inside the breasts.

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. In females, the reproductive phase of life begins at puberty ( 10 to 12 years of age) and generally lasts till the age of approximately 45 to 50 years. The ova begin to mature with the onset of puberty. One ovum matures and is released by one of the ovaries once in about 28 to 30 days. During this period, the wall of the uterus becomes thick so as to receive the egg in case it is fertilized and the zygote begins to develop. This results in pregnancy.

If fertilization does not occur, the released egg, and the thickened lining of the uterus along with its blood vessels are shed off. This causes bleeding in women which is called menstruation. Initially, menstrual cycle may be irregular. It takes some time to become regular.

Menstruation occurs once in about 28 to 30 days. The first menstrual flow begins at puberty is termed menarche. At 45 to 50 years of age, the menstrual cycle stops. Stoppage of menstruation is termed menopause.

Reproductive health in humans: The physical and mental well being of an individual is regarded as an individual's health.

1. Nutritional needs of the adolescents: A balanced diet means that the meals include various nutrients like proteins, carbohydrates, fats, vitamins etc. in requisite proportions. Our Indian meal of 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. Iron builds blood and iron-rich food such as leafy vegetables, jaggery, meat, citrus, Indian gooseberry (amla) are good for adolescents.

Chips and packed or tinned snacks, though very tasty should never replace regular meals as they do not have adequate nutritional value.

2. Personal hygiene: Everyone should have a bath at least once every day. It is more necessary for teenagers because the increased activity of sweat glands sometimes makes the body smelly. All parts of the body should be washed and cleaned every day. If cleanliness is not maintained there are chances of catching bacterial infection. Girls should take special care of cleanliness during the time of menstruation.
3. Physical exercise: Walking and playing in fresh air keep the body fit and healthy. All young boys and girls should take walks, exercise and play outdoor games.

4. Say "NO" to drugs and alcohols: 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 will feel like taking them again and again. They harm the body in the long run. They ruin health and happiness.

Adolescent pregnancy: The legal age for marriage is 18 years for girls and 21 years for boys. This is because teenage mothers are not prepared mentally or physically for motherhood. Early marriage and motherhood cause health problems in the mother and the child.

5.0AIDS (Acquired Immuno-Deficiency Syndrome)

AIDS is a disease which is caused by HIV (Human immuno-deficiency virus). This virus destroys the natural defence mechanism of the body and makes it susceptible to diseases.

6.0Transmission of AIDS

(i) Sharing the needle of the syringe for injecting drugs. (ii) Unprotected sex with an infected person. (iii) Transfusing blood into the body of a healthy person from an infected person. (iv) Infected mother can pass HIV virus through milk to an infant.

How to Prevent AIDS

(i) Use disposable syringes. (ii) Get blood from registered blood banks for transfusion. (iii) Have safe and protected sex. (iv) HIV infected mother should not breast feed her baby.

Sex determination in human: The sex of the baby is determined by the sex chromosomes XX and inside the fertilised egg or zygote.

The 23rd pair of chromosomes differs in males and females. These two chromosomes, which determine the sex of an individual, are called sex chromosomes or allosomes and are indicated by the letters X and Y .

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 chromosomes, while a male has one and one chromosome. The gametes (egg and sperm) have only one set of chromosomes. The unfertilized egg always has one X chromosome. But sperms are of two kinds. One kind has an X chromosome, and the other kind has a Y chromosome.

When a sperm containing X chromosome fertilizes the egg, the zygote would have two X chromosomes and develops into a female child. If the sperm contributes a chromosome to the egg (ovum) at fertilization, the zygote will develop into a male child. The sex chromosomes of the father determine the sex of an unborn baby.

• The belief that the mother is responsible for the sex of her baby is completely wrong and to blame her for this is totally unjustified. The instruction for determining the sex of the baby is present inside the fertilized egg or zygote. This instruction is present in the thread-like structures, called chromosomes in the fertilized egg.

Sex determination in humans

1. The sex of the baby is determined by the sex chromosomes and inside the fertilized egg or zygote.
2. The zygote would have two chromosomes and develops into a female child.
3. At fertilization, the zygote would have one and chromosomes which develops into a male child.
4. No, the sex of the baby is determined by the male sex chromosomes or which is inside the fertilised egg or zygote.

7.0Chapter At a Glance

8.0Some Basic Terms

1. Adam's Apple: Protruding part of the throat (Growing voice box in boys)
2. Testes: Male sex organs
3. Ovaries: Female sex organs
4. Hormone: Chemical substances secreted from the endocrine glands.
5. Endocrine glands: Ductless glands
6. Testosterone: Male sex hormone
7. Estrogen: Female sex hormone
8. Menopause: Stoppage of menstruation
9. Menarche: First menstrual flow begins at puberty
10. AIDS: Acquired immuno-deficiency syndrome

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