Reaching the Age of Adolescence

Track Your Progress

1. a. Testosterone 

    b. Sebaceous glands 

c. Endocrine glands

d. Mammary gland 

e. Larynx

2. 

a. Thyroid 

b. Thyroid 

c. Female

d. Iodine

e. Sweat glands

Assessment Zone

A. Choose the correct answer.

1. b 

2. c 

3. c 

4. a 

5. a

6. a 

7. b 

8. c 

9. c

B. Answer in one word.

1. Puberty

 2. Male

 3. Goitre

4. Thyroxine 

5. Metamorphosis

C. State True or false.

 1. True

 2. False 

 3. True 

 4. True

 5. False

D. Given below are the situations that could happen due to lack of a certain hormones. Identity the hormone in each situation.

1. Insulin

2. Growth hormone 

E. Complete the crossword with the help of the clues provided below.

Across

3. Hormones  

6. Menopause

 7. Insulin

  8. Adam’s apple

 10. Testes

Down

1. Oestrogen 

2. Pheromones 

4. Pituitary

5. Adrenaline 

9. Sebaceous

F. Answer the following questions in brief.

 1. Puberty is the period of onset of sexual maturity in humans and involves distinct

physical changes in the body. During this stage, both the male and the female

reproductive organs become functional, making the individuals capable of reproduction.

2. Five changes that occur in the human male body at puberty are listed below:

    • Secondary sexual characteristics like moustache, beard, hair on the chest and

Adam’s apple develop during puberty.

    • The adult male develops a large voice box or larynx which makes their voice deeper.

  • Manifestation of acne and pimples, especially on the face due to activation of sweat

producing glands and the sebaceous glands.

  • There is a sudden change in physical appearance like increase in the length of bones

of the legs and the arms. In males, the shoulders broaden, the chest widens and

there is increase in muscle mass.

  • The testes in the males start producing sperms. The penis and testicles in males are

fully developed.

3. Hormones regulate and influence the changes associated with puberty. At puberty, the

testes of human male produce a hormone called testosterone. It is this testosterone that

regulates the development of secondary sexual characters and leads to the maturation

of the accessory sex organs (organs of reproductive system but not involved in gamete

production). Testosterone also regulates sperm production in the males. The ovaries

of human female produce the female hormones, for example, oestrogen which helps

in regulating the menstrual cycle, development of secondary sexual characters and

accessory sex organs.

4. a. The sweat producing glands, the oil glands or the sebaceous glands get activated and

produce more of their secretions which cause acne and pimple.

b. Metamorphosis of tadpole into frog takes place only in the presence of the hormone

thyroxine. Since the secretion of this hormone requires sufficient amounts of iodine,

tadpoles need to live in salt water.

5. Sex organs develop during adolescence because testosterone and oestrogen is secreted at

puberty. It is these hormones that bring about changes in the human male and female.

Initially, the body is not capable of performing sexual activities in order to produce its

off springs, hence the primary organs required from the birth develop first and the sex

organs fully develop at adolescent age along with secondary sexual characters.

  6. Over-secretion of growth hormone causes an exceptional increase in the length of

a person, a condition called gigantism. Under-secretion of this hormone causes an

abnormally short stature, a condition called dwarfism.

  7. Goitre describes a condition where the thyroid gland, located in the neck, becomes

enlarged. It is one of the most common thyroid disorders. Thyroxin hormone requires

iodine for its formation. Lack of iodine can cause goitre.

8. AIDS (Acquired Immune Deficiency Syndrome) can spread by using infected needles,

blood transfusion from an infected individual, through infected mother to her baby by

breast feeding or by having sexual contact with an infected individual.

9. Testicles (male) and ovaries (female) develop during puberty.

10. Insects such as ants also secrete some hormones called pheromones. Pheromones help

these insects to track more of their kind and to raise alarms during life-threatening

situations

G. Answer the following questions in detail.

1. The sex of a baby is determined by the chromosomes present in the male and the female

gametes involved in reproduction. Most mammals, including humans, have an XY sex-

determination system: the Y chromosome carries factors responsible for triggering male

development. Thus, male mammals typically have an X and a Y chromosome (XY),

while female mammals typically have two X chromosomes (XX). Chromosomal sex is

determined at the time of fertilisation; a chromosome from the sperm cell, either X or Y,

fuses with the X chromosome in the egg cell.

  XX will be a female.

2. Refer to fig no. 10.4 on page no. 142.

3. At puberty, there is development of secondary sexual characters.

 In females, breasts are a manifestation of higher levels of estrogen; estrogen also

widens the pelvis and increases the amount of body fat in hips, thighs, buttocks, and

breasts. Estrogen also induces growth of the uterus, proliferation of the endometrium,

and menses.

    • Enlargement of breasts.

    • Growth of body hair, most prominently underarm and pubic hair

    • Greater development of thigh muscles behind the femur, rather than in front of it (as

is typical in mature males)

  • Widening of hips; lower waist to hip ratio than adult males.

 In males, testosterone directly increases size and mass of muscles, vocal cords,

and bones, deepening the voice, and changing the shape of the face and skeleton.

It accelerates growth of androgen-responsive facial and body hair but may slow

and eventually stop the growth of head hair. Taller stature is largely a result of

later puberty.

• Growth of body hair, including underarm, abdominal, chest hair and pubic hair. Loss

of scalp hair due to androgenic alopecia can also occur.

    • Greater mass of thigh muscles in front of the femur, rather than behind it (as is

typical in mature females)

  • Growth of facial hair.

    • Enlargement of larynx (Adam’s apple) and deepening of voice.

    • Increased stature; adult males are taller than adult females, on average.

  4. The sequence of events involving maturation of an ovum, ovulation and menstrual

flow constitutes a cycle called the menstrual cycle. Ovulation occurs in the middle of

the menstrual cycle. The monthly cycle of changes in the ovaries and the lining of the

uterus (endometrium), starting with the preparation of an egg for fertilisation. When

the follicle of the prepared egg in the ovary breaks, it is released for fertilisation and

ovulation occurs. Unless pregnancy occurs, the cycle ends with the shedding of part of

the endometrium, which is menstruation. Although it is the end of the physical cycle,

the first day of menstrual bleeding is designated as “day 1” of the menstrual cycle in

medical parlance.

5. Practices which can be adopted by the adolescents to maintain personal hygiene:

    • One must bathe regularly and keep the pubic region neat and clean, otherwise it

could lead to bacterial or fungal infection.

  • Pay extra attention to those hairy parts particularly the armpits and groin where

there are many sweat producing glands and where bacteria grow quickly.

    • Girls maintain personal hygiene during menstruation by keeping themselves clean

and changing sanitary napkin frequently.

  6. Differences between enzymes and hormones:

    • Hormones are chemical messengers whereas enzymes are biological catalysts. Mostly

enzymes perform reactions at the place of origin i.e. in cells where they are produced.

Hormones are released by the glands directly into the blood stream which then

travel in whole body reaching their target organ or parts. This implies that the site

of origin and site of action of hormones are different

    • Enzymes are biological catalyst. They catalyse the biological reactions. Hormones

are not catalyst. They simply initiate biochemical reactions.

  • All enzymes are generally proteins. There are some exceptions like ribozymes (RNA

with catalytic activity). The hormones may be polypeptides, terpenoids, steroids,

phenolics compounds or amines.

  • As enzymes are catalyst, at the end of reaction they remain unchanged and can be

reutilised. As hormones are not catalyst, they participate in biological reaction and

their chemical composition is changed and cannot be reutilised as such.

7. A gland is different from any other organ of the body.

  • Gland is a specialised cell or group of cells synthesise and secrete substances.

However, organ is a group of organised tissues performing specific or group of

functions.

  • Gland always secretes substances but not all the organs secrete substances.

    • Gland is always a tube like structure but organ is not always in that nature. For

example, liver is a dense organ but stomach is a hollow organ.

    • Gland is technically a collection of cells, which are of the same type. However, many

other organs have different types of cells.

• The functionally related organs perform functions together as a unit called organ

systems, which involves in homeostasis, but glands alone do not function together

always.

  • An animal cannot live without vital organ. If the essential substances are provided

externally, the animal can live without that particular gland.

    • Normally most of the organs are larger and complex compared to glands.

  8. Hormones also play important roles in the lives of organisms other than humans also.

For example, metamorphosis, the process through which tadpoles turn into frogs, takes

place only in the presence of the hormone thyroxine. Since the secretion of this hormone

requires sufficient amounts of iodine, tadpoles need to live in salt water. If the water in

which tadpoles are present is not salty, they do not mature into frogs. Insects such as

ants also secrete some hormones called pheromones. Pheromones help these insects to

track more of their kind and to raise alarms during life-threatening situations

9. A few things must be kept in mind in order to make responsible decisions during

adolescence:

  • Analyse every situation carefully before determining your course of action. Try to

understand why a person is giving you a certain piece of advice before coming to a

conclusion.

  • Peer pressure shows a considerable effect on teenagers during this time, but always

feel free to refuse to do something that you feel is wrong.

    • Puberty or sexual maturity, may also bring about sexual feelings or feelings of

attraction towards the opposite sex. However, we must remember that this time of

life may be as confusing for our friends as it is for us. Hence, we must respect and

support each other during this time.