This chapter talks about physical and hormonal changes leading upto reproductive maturity
We have learnt in the chapter ‘Reproduction in Animals’, that only after human beings and animals reach a certain age, they can reproduce.
Growing up is a natural and ongoing process in one’s life & growth begins from the day one is born.
Adolescence is that period of life, when the body undergoes changes, leading to reproductive maturity. It begins around the age of 11 & lasts upto 18 or 19 years of age. As this period covers the ‘teens’, adolescents are also called as ‘Teenagers’.
Puberty is the process of physical changes by which a child’s body becomes an adult and becomes capable of reproduction.
The following changes occur at Puberty
The most visible change during puberty is the sudden increase in height, as during this time, the long bones, that is, the bones of the arms & the legs elongate & make a person tall. Both boys & girls reach their maximum height by the time they reach the age of 18. The growth rate varies from individual to individual. The maximum height a person will acquire depends on the genes inherited from parents. Adequate nourishment is also required for the bones, muscles & other body parts for growth.
The changes that occur in boys during adolescence is different from the changes occurring in girls.
In boys, the body muscles grow more prominently & their shoulders broaden.
In girls, the region below the waist becomes wider.
There is a noticeable change in the voice of boys during puberty. Their voice begins to crack & becomes deeper over a period of time. It is so because, boys have larger voice bones. The growing voice bon can be noticed as a protruding part of the throat & is called as Adam’s apple. There is no noticeable change in the voice of the girls during puberty.
During puberty, the secretion of sweat glands & sebaceous glands (oil producing glands) increases. Due to increased activity of sebaceous glands, lots of people get Acne
At puberty, male sex organs like testes and penis develop completely and the testes also begin to produce sperms. In girls, the ovaries enlarge & eggs begin to mature & ovaries start releasing mature eggs.
During this phase, a child goes through many mental and emotional changes. Some of them are listed below
Secondary Sexual characters are the features which help to distinguish the males from the females.
The following are the secondary sexual characters of males
The following are the secondary sexual characters of females
The changes at puberty in males and females are triggered by secretion of male and female hormones respectively. Hormones are chemical substances produced by the endocrine glands. Male hormone is called Testosterone and female hormone is called Estrogen
Endocrine glands are such glands that produce their secretions (hormones) directly into the blood rather than through a duct. For example
Pituitary gland is small (about 0.5 grams in weight) pea sized gland, present in brain. It secretes various hormones in blood, which stimulate the target sites (testes and ovaries) to secrete their hormones.
Testosterone and Estrogen released by these glands is again released into the blood and reaches the target sites to trigger various body changes such as growth of facial/pubic hair and growth of breasts & mammary (milk producing) glands.
Adolescents become capable of reproduction when their testes & ovaries begin to produce gametes. The capability for maturation & production of gametes lasts for a much longer time in males than in females.
The reproduction phase of females starts at puberty (at the age of 10-12 years) & generally lasts till the age of approx 45-50 years.
Menarche – The first menstrual flow in females begins at puberty and is called menarche. Once started, menstruation occurs once in about 28-30 days.
Menopause – The stopping of menstrual cycle is called as Menopause. Menopause occurs at the age of 45-50 years.
Menstrual Cycle consists of the following phases. This cycle repeats every 28 days.
Gametes (egg and sperm) contain thread-like structures called chromosomes, which contain genetic material. Both egg and sperm have 23 pairs of chromosomes. Out of these, 2 chromosomes determine the sex of the zygote. These are called X and Y chromosomes.
Eggs have 2 X chromosomes while sperms contain 1 X and 1 Y chromosome. When an egg is fertilized by a sperm, the resultant zygote may contain
In both the above cases, it is the variation of the chromosome contributed by the sperm that results in different sex of the child.
There are multiple endocrine glands in human body and have different functions. In addition to Ovaries and Testes, the following are the other important glands
Hormones are present in animals as well. Metamorphosis (change from Larva to adult) in insects is controlled by insect hormones.
In Frog, the metamorphosis is controlled by hormone thyroxine, which is 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.
Every individual needs to have a well balanced diet for physical & mental well being. However, during adolescence, the need for a well balanced is more because the body is growing.
The diet of an adolescent has to be a well balanced diet which includes proteins from all the food groups like dal, vegetable, roti/rice. Fruits also provide nourishment. Milk is a balanced food in itself. Iron builds blood & iron rich food such as leafy vegetables, jaggery, meat and amla are good for adolescents.
As sweat glands are more active in adolescents, all body parts should be washed & cleaned every day. If hygiene is not maintained, there may be chances of catching bacterial infections.
All young boys & girls should play outdoor games as it keeps the body fit & healthy.
During adolescence, the body & mind are very active and it is a part of growing up. Sometimes, adolescents feel confused & insecure. During this period of insecurity, if someone suggests to try Drugs, as they give relief, do not believe them & say ‘No’ to drugs as they are addictive.
HIV (Human Immunodeficiency Virus) is a dangerous virus which causes AIDS (Acquired Deficiency Syndrome). There is currently no cure for this disease. It gets transmitted by the following ways