Notes on “Reaching
the Age of Adolescence” Chapter-7, by
Md. Farrukh Asif
In the earlier chapter, you learned
about the reproduction process in animals. Human beings and many other animals
can only reproduce after reaching a specific age. What causes humans to be able
to reproduce only after they reach a certain age? In this chapter, you will
explore the changes that occur in the human body that enable a person to become
capable of reproduction. In Chapter 6, you studied the human reproductive
organs. Here, we will examine the role of hormones in facilitating the changes
that allow a child to develop into an adult.
Adolescence and Puberty:
Growth starts from the moment a
person is born. However, after reaching the age of 10 or 11, there is a
noticeable increase in growth. The transformations occurring in the body are
part of the maturation process. They signal that one is transitioning from
childhood to adulthood. Maturing is a natural phenomenon. The stage of life
characterized by bodily changes that lead to reproductive capability is
referred to as adolescence.
Adolescence typically starts around
the age of 11 and can last until 18 or 19 years old. Since this phase coincides
with the ‘teen’ years (ages 13 to 18 or 19), those in this stage are often
labeled as ‘teenagers’. In girls, the onset of adolescence can occur a year or
two earlier than in boys. Additionally, the duration of adolescence can differ
among individuals. During adolescence, the human body experiences numerous
changes. These alterations signify the beginning of puberty. The primary change
that indicates puberty is when boys and girls gain the ability to reproduce.
Puberty concludes when an adolescent achieves reproductive maturity.
Changes at Puberty
Increase in Height
The most obvious change during
puberty is the rapid increase in height. At this stage, the long bones, which
are the bones in the arms and legs, stretch and contribute to a person's
height. Initially, girls tend to grow quicker than boys, but by around 18 years
of age, both genders usually reach their full height. The growth rate in height
differs among individuals; some may experience a sudden height increase during
puberty, while others may grow at a more gradual pace. There’s no reason for
Paheli to be concerned; not all body parts grow at the same rate. Sometimes,
during adolescence, the arms and legs or hands and feet may appear larger and
disproportionate compared to the rest of the body. However, eventually, the
other body parts will develop to achieve a balanced physique. You may have
observed that an individual's height often resembles that of a family member.
This is due to height being influenced by genetic factors inherited from
parents. Nevertheless, it is crucial to consume the appropriate types of food
during these developmental years, as this ensures that bones, muscles, and
other body parts receive sufficient nutrition for growth. The nutritional
requirements for adolescents will be elaborated on later in the lesson.
Change in Body Shape
Have you observed that the boys in
your class tend to have wider shoulders and chests compared to those in the
lower grades? This is due to the onset of puberty, during which boys typically
experience broader shoulders as they grow. In females, the area below the waist
usually expands. In males, their muscles tend to develop more noticeably than
in females. Therefore, the changes that occur during adolescence in boys and
girls differ from one another.
Voice Change
Have you ever
noticed that the voices of some boys in your class occasionally crack? During
puberty, the larynx or voice box starts to develop. Boys experience an increase
in the size of their voice boxes. This growth can be observed in boys as a
noticeable bulge in the throat known as the Adam’s apple (Fig. 7.2). In
contrast, girls have a less prominent larynx due to its smaller size.
Typically, girls possess a higher-pitched voice, while boys have a
lower-pitched voice. In teenage boys, the muscles in the expanding voice box
may become uncoordinated at times, leading to a hoarse voice. This condition
may persist for a few days or weeks before the voice returns to normal.
Fig. :
Adam’s apple in a grown up boy
and pimples on the face at this time
because of the increased activity of these glands in the skin.
Development of Sex Organs
Look up Fig. 6.1 and 6.3 of the
previous lesson which shows the sex organs of humans.
Fig: Male & Female
reproductive organs in humans
During puberty, male reproductive
organs such as the testes and penis undergo complete development. The testes
also commence sperm production. In females, the ovaries increase in size and
begin the maturation of eggs. Additionally, the ovaries start to release mature
eggs. Attaining mental, intellectual, and emotional maturity, adolescence marks
a shift in how a person thinks. Adolescents are more autonomous than they were
earlier and often feel self-conscious. Intellectual growth occurs, and they
tend to invest a significant amount of time in contemplation. In fact, this
period in life is when the brain is most capable of learning. However, some
adolescents may experience feelings of insecurity as they adapt to bodily and
mental changes. Yet, as adolescents, it is important to understand that feeling
insecure is unnecessary. These transformations are a normal aspect of growing
up.
Secondary Sexual Characters
In Chapter 6, you learned that the
testes and ovaries serve as the reproductive organs. They produce gametes,
which are sperm and ova. During puberty, girls experience breast development,
while boys start to grow facial hair, including moustaches and beards. These
characteristics, which help differentiate males from females, are termed
secondary sexual traits. Boys also develop hair on their chests. In both
genders, hair appears under the arms and around the pubic region. The
transformations that take place during adolescence are regulated by hormones.
Hormones are chemical substances produced by the endocrine glands, part of the
endocrine system. At puberty, the testes begin releasing the male hormone,
testosterone. This hormone triggers the changes in boys that you have just
learned about, such as the growth of facial hair. Once girls reach puberty,
their ovaries start producing the female hormone, estrogen, which initiates
breast development. The mammary glands that produce milk also develop within
the breasts. The secretion of these hormones is regulated by another hormone
released by the pituitary gland, an endocrine gland.
Role of Hormones in Initiating
Reproductive Function
Endocrine glands release hormones
into the bloodstream to reach a particular body part called the target site. The
target site responds to the hormone. There are many endocrine glands or
ductless glands in the body.
The testes and ovaries secrete sex
hormones. You have just learnt that these hormones are responsible for male
and female secondary sexual characters. Further, the sex hormones are under the
control of hormones from the pituitary gland (Fig.). The pituitary secretes
many hormones, one of which makes ova mature in the ovaries and sperms form in
the testes.
Reproductive Phase of Life
in Humans
Adolescents gain the ability to
reproduce when their testes and ovaries start producing gametes. In males, the
ability to mature and produce gametes continues for a significantly longer
duration compared to females. In females, the reproductive phase commences at
puberty, typically between the ages of 10 and 12, and generally extends until
around 45 to 50 years of age. The maturation of ova begins with the onset of
puberty. Approximately every 28 to 30 days, one ovum matures and is released
from one of the ovaries. During this time, the uterine lining thickens in
preparation to receive a fertilized egg for potential development, which can
lead to pregnancy. If fertilization does not occur, the released egg along with
the thickened uterine lining and its blood vessels are expelled, resulting in
the bleeding known as menstruation. Menstruation typically happens every 28 to
30 days. The initial menstrual flow begins at puberty and is referred to as
menarche. The menstrual cycle generally ceases around the ages of 45 to 50, a
process known as menopause. Initially, the menstrual cycle may be irregular and
takes time before it becomes consistent.
The menstrual cycle is
regulated by hormones. The cycle involves the maturation and release of the
egg, the thickening of the uterine lining, and its disintegration if
fertilization does not take place. If the egg is fertilized, it starts dividing
and subsequently implants itself in the uterus for further growth, as you learned in the previous
chapter.
How is the Sex of the Baby
Determined?
Boy or Girl?
Within the fertilized egg, or zygote,
lie the instructions that determine the baby's sex. These instructions are
found in thread-like structures known as chromosomes, located in the fertilised
egg. Chromosomes are contained within the nucleus of every cell. Humans possess
23 pairs of chromosomes within the nuclei of their cells. Out of these, two
chromosomes are designated as sex chromosomes, referred to as X and Y. A female
has two X chromosomes, whereas a male has one X and one Y chromosome. The gametes
(egg and sperm) contain only one set of chromosomes. The unfertilised egg
carries one X chromosome. In contrast, sperm come in two types: one type
carries an X chromosome, and the other carries a Y chromosome.
When a sperm
that carries an X chromosome fertilises the egg, the resulting zygote will have
two X chromosomes and will develop into a female child. Conversely, if a sperm
contributes a Y chromosome to the egg (ovum) during fertilisation, the zygote
will develop into a male child.
Hormones other than Sex
Hormones
Look at Fig. again. The hormones
secreted by the pituitary stimulate testes and ovaries to produce their hormones.
You have already learnt that the pituitary gland is an endocrine gland. It is
attached to the brain. Apart from the pituitary, the testes and the ovaries,
there are other endocrine glands in the body such as the thyroid, pancreas and
adrenals (Fig.).
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KEYWORDS
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ADAM’S APPLE
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ADOLESCENCE
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ADRENALIN
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BALANCED DIET
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ENDOCRINE GLANDS
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ESTROGEN HORMONES
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INSULIN
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LARYNX
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PITUITARY
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GLAND
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PUBERTY
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REPRODUCTIVE HEALTH
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SECONDARY SEXUAL CHARACTERS
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SEX CHROMOSOMES
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TARGET SITE
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TESTOSTERONE
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THYROXINE
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VOICE BOX
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A Complete Solution
of “Reaching The Age of Adolescence” Ch-7, by Md. Farrukh Asif
Exercises
Question 1
What is the term used for chemical
secretions of endocrine glands responsible for changes taking place in the
body?
Answer
The term used for chemical secretions
of endocrine glands responsible for changes taking place in the body is
Hormones.
Question 2
Define adolescence.
Answer
The period of life, when the body
undergoes changes, leading to reproductive maturity, is called adolescence. In
other words, adolescence is transitional phase of growth and development
between childhood and adulthood.
Question 3
What is menstruation? Explain.
Answer
In females, with the onset of
puberty, the ova begins to mature. 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. If fertilisation 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. Menstruation occurs once in about 28 to 30 days.
Question 4
List changes in the body that take
place at puberty.
Answer
Following are the changes that take
place at puberty :
1. The body becomes capable of reproduction.
2.
Sudden
increase in height.
3.
Growth
in shoulders and muscles in boys
4.
Change
in voice and protruding voice box or the larynx in boys
5.
The
secretion of sweat glands and sebaceous glands (oil glands) increases causing
acne.
6.
At
puberty, male sex organs like the testes and penis develop completely. The
testes also begin to produce sperm.
7.
Boys
begin to grow facial hair, that is, mustaches and beards. Boys also develop
hair on their chest, underarms, and pubic area.
8.
Development
of breasts in girls.
9.
In
girls, the region below the waist becomes wider.
10. The ovary matures and begins to release the egg.
11. Girls develop hair in the underarm and pubic area.
Question 5
Prepare a Table having two columns
depicting names of endocrine glands and hormones secreted by them.
Answer
Below table shows the names of
endocrine glands and hormones secreted by them:
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Endocrine gland
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Hormones
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Testis
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Testosterone
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Ovary
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Oestrogen
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Thyroid
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Thyroxin
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Adrenal
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Adrenalin
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Pituitary
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Growth hormone
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Pancreas
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Insulin
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Question 6
What are sex hormones? Why are they
named so? State their function.
Answer
Hormones released from sex organs are
referred as sex hormones. They are named so because they affect the sexual
organs and characters.
The sex hormones and their functions
are as follows :
1. The male sex hormone is Testosterone released from the testis. Testosterone induces
puberty-related physical changes, including increased muscle, face, pubic, and
body hair growth, voice deepening, and sexual and reproductive development.
2. The female sex hormone is estrogen which is released from the ovary. It plays a role in the maintenance of the menstrual cycle and development of breasts.
Question 7(a)
Adolescents should be careful about
what they eat, because
1. A proper
diet develops their brains.
2. A proper
diet is needed for the rapid growth taking place in their body.
3.
adolescents
feel hungry all the time.
4.
taste
buds are well-developed in teenagers.
Answer
proper diet is needed for the rapid
growth taking place in their body.
Reason — Adolescence is a period
of rapid growth. Therefore, a proper growth requires ample nutrition.
Question 7(b)
Reproductive age in women starts when
their
1.
menstruation
starts.
2.
breasts
start developing.
3.
body
weight increases.
4.
height
increases.
Answer
menstruation starts.
Reason — The start of menstruation
marks end of puberty and start of reproductive age.
Question 7(c)
The right meal for adolescents
consists of
1.
chips,
noodles, coke.
2.
chapati,
dal, vegetables.
3.
rice,
noodles and burger.
4.
vegetable
cutlets, chips and lemon drink.
Answer
chapati, dal, vegetables.
Reason— Junk food will not provide
the required amount of nutrition.
Question 8
Write notes on :
(a) Adam's apple.
(b) Secondary sexual characters.
(c) Sex determination in the unborn
baby.
Answer
(a) Adam's apple — 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. Sometimes, the muscles of the growing voice box go
out of control and the voice becomes hoarse. This state may remain for a few
days or weeks after which the voice becomes normal.
(b) Secondary sexual
characters — Secondary sexual characters are responsible for the features
that help to distinguish the male from the female. Secondary sexual characteristics
in boys are the development of pubic hair, facial hair, and hair on the chest. The development of breast in girls is also a secondary sexual character.
(c) Sex determination in the
unborn baby — 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
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 an X chromosome fertilises the egg, the zygote would have two X
chromosomes and develop into a female child. If the sperm contributes a Y
chromosome to the egg (ovum) at fertilisation, the zygote would develop into a
male child.
Question 9
Word game: Use the clues to work out
the words.
Across
3. Protruding voice box in boys.
4. Glands without ducts.
7. Endocrine gland attached to brain.
8. Secretion of endocrine glands.
9. Pancreatic hormone.
10. Female hormone.
Down
1. Male hormone.
2. Secretes thyroxine.
3. Another term for teenage.
5. Hormone reaches here through blood stream.
6. Voicebox.
7. Term for changes at adolescence.
Answer
The solution of word puzzle is given
below:
Across
3. Adam's Apple.
4. Endocrine.
7. Pituitary.
8. Hormone.
9. Insulin.
10. Estrogen.
Down
1. Testosterone.
2. Thyroid.
3. Adolescence.
5. Target Site.
6. Larynx.
7. Puberty.
Question 10
The table below shows the data on
likely heights of boys and girls as they grow in age. Draw graphs showing
height and age for both boys and girls on the same graph paper. What
conclusions can be drawn from these graphs?
Answer
The following conclusions can be
drawn from these graphs:
1.
From
0 to 8 years, the height of boys increases more than girls so boys are generally a
little taller than girls in this age group.
2.
Both
boys and girls experience a sudden increase in height during puberty.
3.
At
the onset of puberty when the adolescence period starts (around 12 years),
height of girls show a sudden increase and they become taller than boys.
4.
Around
the age of 16, the height of boys catches up with girls and both are equally tall.
5.
Afterwards,
the height increases and becomes stable around 20 years of age with the height of
boys being a little more than girls.
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KEYWORDS
ADAM’S APPLE
ADOLESCENCE
ADRENALIN
BALANCED DIET
ENDOCRINE
GLANDS
ESTROGEN HORMONES
INSULIN
LARYNX
PITUITARY GLAND
PUBERTY
REPRODUCTIVE HEALTH
SECONDARY SEXUAL CHARACTERS
SEX CHROMOSOMES
TARGET SITE
TESTOSTERONE
THYROXINE
VOICE BOX
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See You Again
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