Reaching the Age of Adolescence PDF

REACHING THE AGE OF ADOLESCENCE I n the previous chapter, you have no longer a child but are on the way to learnt how animals reproduce. It is becoming an adult. only after ëgrowing upí to a certain age that human beings and many other animals can reprod...

REACHING THE AGE OF ADOLESCENCE I n the previous chapter, you have no longer a child but are on the way to learnt how animals reproduce. It is becoming an adult. only after ëgrowing upí to a certain age that human beings and many other animals can reproduce. Why can I wonder how long this humans reproduce only after a certain period marked by changes age? in the body will last! In this chapter, you will learn about changes that take place in the human body after which a person becomes capable of reproduction. It is a strange period of life In Chapter 9, you have learnt about when you are neither a child nor human reproductive organs. Here, we an adult. I wonder whether this shall discuss the role that hormones play period between childhood and in bringing about changes that make a adulthood had a special name! child grow into an adult. Growing up is a natural process. The 10.1 Adolescence and Puberty period of life, when the body undergoes changes, leading to reproductive Boojho was celebrating his 12th maturity, is called adolescence. birthday. After his friends left, Boojho Adolescence begins around the age of and Paheli began chatting with their 11 and lasts upto 18 or 19 years of age. parents. Paheli studies in an all-girls Since this period covers the ëteensí (13 school. She started laughing. She to 18 or 19 years of age), adolescents remarked that many of Boojhoís school are also called ëteenagersí. In girls, friends, whom she met after a year, had adolescence may begin a year or two suddenly shot up in height. Some of earlier than in boys. Also, the period of them were looking very funny with a adolescence varies from person to person. hairy line above their lips. Her mother The human body undergoes several explained that the boys had grown up. changes during adolescence. These Growth begins from the day one is changes mark the onset of puberty. The born. But upon crossing the age of 10 most important change which marks or 11, there is a sudden spurt in growth puberty is that boys and girls become which becomes noticeable. The changes capable of reproduction. Puberty ends taking place in the body are part of when an adolescent reaches reproductive growing up. They indicate that you are maturity.  the tallest and who might be the shortest in your class. Paheli and Boojho realised that sudden Age in % of full height increase in height and hairy line above the lips Years Boys Girls in boys were signs of adolescence. They 8 72% 77% wanted to know more about other changes at 9 75% 81% puberty. 10 78% 84% 11 81% 88% 12 84% 91% 10.2 Changes at Puberty 13 88% 95% Increase in Height The most conspicuous change during 14 92% 98% puberty is the sudden increase in 15 95% 99% height. At this time the long bones, that is, the bones of the arms and the legs 16 98% 99.5% elongate and make a person tall. 17 99% 100% Activity 10.1 18 100% 100% The following chart gives the average rate of growth in height of boys and girls with age. The figures in columns 2 and 3, give the Calculation for full height (cm) percentage of the height a person Present height (cm) has reached at the age given in × 100 % of full height at this age column 1. For example, by the age (as given in the chart) 11, a boy has reached 81% of his probable full height, while a girl Example: has reached 88% of her full height. These figures are only A boy is 9 years old and 120 cm representative and there may be tall. At the end of the growth period individual variations. he is likely to be Use the Table for your friends and work out how tall they are likely 120 × 100 cm = 160 cm tall to be. Find out who is likely to be 75 114 SCIENCE Activity 10.2 There is no need for Paheli to worry. All parts of the body do not grow at the Use the data given in Activity 10.1 same rate. Sometimes the arms and legs to draw a graph. Take age on the X- or hands and feet of adolescents look axis and per cent growth in height oversized and out of proportion with the on the Y-axis. Highlight the point body. But soon the other parts catch representing your age on the graph. up and result in a proportionate body. Find out the percentage of height You must have noticed that height you have already reached. Calculate the height you might eventually of an individual is more or less similar reach. Tally your graph with the one to that of some family member. This is given here (Fig. 10.1). because height depends on the genes inherited from parents. 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 get adequate nourishment for growth. You will find nutritional needs of adolescents discussed later in the lesson. Change in Body Shape Have you noticed that boys in your class have broader shoulders and wider chests than boys in junior classes? This is Fig. 10.1 : Graph showing percentage of height because they have entered the age of with age puberty when shoulders generally broaden as a result of growth. In girls, Initially, girls grow faster than boys the region below the waist becomes but by about 18 years of age, both reach wider. their maximum height. The rate of In boys, the muscles of the body grow growth in height varies in different more prominently than in the girls. individuals. Some may grow suddenly Thus, changes occurring in adolescent at puberty and then slow down, while boys and girls are different. others may grow gradually. Voice Change Did you notice that sometimes the voice of some of the boys in your class cracks? I am worried. Though I At puberty, the voice box or the larynx have become taller, my face looks much smaller begins to grow. Boys develop larger voice compared to my body. boxes. The growing voice box in boys can be seen as a protruding part of the throat REACHING THE AGE OF ADOLESCENCE 115 called Adam’s apple (Fig. 10.2). In girls, and pimples on the face at this time the larynx is hardly visible from the because of the increased activity of these outside because of its small size. glands in the skin. Generally, girls have a high pitched voice, whereas boys have a deep voice. In Development of Sex Organs adolescent boys, sometimes, the muscles Look up Fig. 9.1 and 9.3 of the of the growing voice box go out of control previous lesson which shows sex and the voice becomes hoarse. This state organs of humans. At puberty, male may remain for a few days or weeks after sex organs like the testes and penis which the voice becomes normal. develop completely. The testes also begin to produce sperms. In girls, the ovaries enlarge and eggs begin to Adamís mature. Also ovaries start releasing apple mature eggs. Reaching Mental, Intellectual and Emotional Maturity Adolescence is also a period of change in a personís way of thinking. Adolescents are more independent than before and are also self conscious. Intellectual development takes place and Fig. 10.2 : Adam’s apple in a grown up boy they tend to spend considerable time thinking. In fact, it is often the time in oneís life when the brain has the greatest capacity for learning. Many of my classmates Sometimes, however, an adolescent may have a hoarse voice. Now I feel insecure while trying to adjust to know why? the changes in the body and mind. But as adolescent learners, you should know Increased Activity of Sweat and that there is no reason to feel insecure. Sebaceous Glands These changes are a natural part of During puberty the secretion of sweat growing up. glands and sebaceous glands (oil glands) increases. Many young people get acne 10.3 Secondary Sexual A few glands such as sweat glands, Characters oil glands and salivary glands release You have learnt in Chapter 9, that their secretions through ducts. testes and ovaries are the reproductive Endocrine glands release hormones organs. They produce the gametes, directly into the bloodstream. So, they that is, sperms and ova. In girls, are also termed ductless glands. breasts begin to develop at puberty 116 SCIENCE and boys begin to grow facial hair, that The testes and ovaries secrete sex is, moustaches and beard. As these hormones. You have just learnt that features help to distinguish the male these hormones are responsible for the from the female they are called male and female secondary sexual secondary sexual characters. Boys characters. Further, the sex hormones also develop hair on their chest. In are under the control of hormones from both, boys and girls, hair grows under the pituitary gland (Fig. 10.3). The the arms and in the region above the pituitary secretes many hormones, one thighs or the pubic region. of which makes ova mature in the ovaries and sperms form in the testes. Both Boojho and Paheli wish to know what initiates changes at puberty. The changes which occur at adolescence are controlled by hormones. Hormones are chemical substances. These are secretions from endocrine glands, or endocrine system. The male hormone or testosterone begins to be released by the testes at the onset of puberty. This causes changes in boys about which you have just learnt, for example, the growth of facial hair. Once puberty is reached in girls, ovaries begin to produce the female hormone or estrogen which makes 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. Fig. 10.3 : The onset of puberty is controlled by 10.4 Role of Hormones in hormones Initiating Reproductive Function Paheli and Boojho have now Endocrine glands release hormones understood that puberty marks the into the bloodstream to reach a beginning of the reproductive period particular body part called target site. when one becomes capable of The target site responds to the reproduction. But they want to know hormone. There are many endocrine if reproductive life, once begun, glands or ductless glands in the body. continues, or it ends some time. REACHING THE AGE OF ADOLESCENCE 117 10.5 Reproductive Phase of Menstrual cycle is controlled by Life in Humans hormones. The cycle includes the maturation of the egg, its release, Adolescents become capable of thickening of uterine wall and its reproduction when their testes and breakdown if pregnancy does not ovaries begin to produce gametes. The occur. In case the egg is fertilised it capacity for maturation and production begins to divide and then gets of gametes lasts for a much longer time embedded in the uterus for further in males than in females. development as you have learnt in In females, the reproductive phase of Chapter 9 (Fig. 9.8). life begins at puberty (10 to 12 years of age) and generally lasts till the age of 10.6 How is the Sex of the approximately 45 to 50 years. The ova Baby Determined? 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 I heard my mother and my period, the wall of the uterus becomes aunt talking about my cousin thick so as to receive the egg, in case who is going to have a baby. it is fertilised and begins to develop. They were discussing whether This results in pregnancy. If she would give birth to a boy fertilisation does not occur, the or a girl. I wonder what makes released egg, and the thickened lining the fertilised egg develop either into a boy or a girl! of the uterus along with its blood vessels are shed off. This causes Boy or Girl? bleeding in women which is called menstruation. Menstruation occurs Inside the fertilised egg or zygote is the once in about 28 to 30 days. The first instruction for determining the sex of menstrual flow begins at puberty and the baby. This instruction is present in is termed menarche. At 45 to 50 years the thread-like structures, called of age, the menstrual cycle stops. chromosomes in the fertilised egg. Stoppage of menstruation is termed Recall from Chapter 8, that menopause. Initially, menstrual cycle chromosomes are present inside the may be irregular. It take some time to nucleus of every cell. All human beings become regular. 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 Paheli says that the chromosomes, while a male has one X reproductive life of a and one Y chromosome. The gametes woman lasts from (egg and sperm) have only one set of menarche to menopause. chromosomes. The unfertilised egg Is she right? always has one X chromosome. But 118 SCIENCE sperms are of two kinds. One kind has and ovaries to produce their hormones. an X chromosome, and the other kind You have already lear nt that the has a Y chromosome. pituitary gland is an endocrine gland. See Fig. 10.4. When a sperm It is attached to the brain. containing X chromosome fertilises the Apart from the pituitary, the testes egg, the zygote would have two X and the ovaries, there are other chromosomes and develop into a female endocrine glands in the body such as child. If the sperm contributes a Y thyroid, pancreas and adrenals chromosome to the egg (ovum) at (Fig. 10.5). fertilisation, the zygote would develop into a male child. pituitary gland sperm thyroid gland adrenal gland eggs pancreas position of the ovary in the female boy girl testis Fig. 10.4 : Sex determination in humans Now you know that the sex chromosomes of the father determine the Fig. 10.5 : Position of endocrine glands in the sex of an unborn baby. The belief that human body the mother is responsible for the sex of Boojho and Paheli had once visited her baby is completely wrong and to their aunt who was a doctor and blame her for this is totally unjustified. remembered that a boy named Kaka had 10.7 Hormones other than a very big and bulging throat. Their aunt had told them that Kaka was suffering Sex Hormones from ëgoitreí, a disease of the thyroid Look at Fig. 10.3 again. The hormones gland. Kakaís thyroid gland was not secreted by the pituitary stimulate testes producing the hormone thyroxine. REACHING THE AGE OF ADOLESCENCE 119