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8 reaching the age of adolescence

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8 reaching the age of adolescence

  1. 1. REACHING THE AGE OF ADOLESCENCEI 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 ‘growing up’ to a certainage that human beings and many otheranimals can reproduce. Why can I wonder how long thishumans reproduce only after a certain period marked by changesage? in the body will last! In this chapter, you will learn aboutchanges that take place in the humanbody after which a person becomescapable of reproduction. It is a strange period of life In Chapter 9, you have learnt about when you are neither a child norhuman reproductive organs. Here, we an adult. I wonder whether thisshall discuss the role that hormones play period between childhood andin bringing about changes that make a adulthood had a special name!child grow into an adult. Growing up is a natural process. The10.1 Adolescence and Puberty period of life, when the body undergoes changes, leading to reproductiveBoojho was celebrating his 12th maturity, is called adolescence.birthday. After his friends left, Boojho Adolescence begins around the age ofand 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 ‘teens’ (13school. She started laughing. She to 18 or 19 years of age), adolescentsremarked that many of Boojho’s school are also called ‘teenagers’. In girls,friends, whom she met after a year, had adolescence may begin a year or twosuddenly shot up in height. Some of earlier than in boys. Also, the period ofthem were looking very funny with a adolescence varies from person to person.hairy line above their lips. Her mother The human body undergoes severalexplained that the boys had grown up. changes during adolescence. These Growth begins from the day one is changes mark the onset of puberty. Theborn. But upon crossing the age of 10 most important change which marksor 11, there is a sudden spurt in growth puberty is that boys and girls becomewhich becomes noticeable. The changes capable of reproduction. Puberty endstaking place in the body are part of when an adolescent reaches reproductivegrowing up. They indicate that you are maturity.
  2. 2. 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 HeightThe most conspicuous change during 14 92% 98%puberty is the sudden increase in 15 95% 99%height. At this time the long bones, thatis, 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 75114 SCIENCE
  3. 3. 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 isFig. 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 becomesbut by about 18 years of age, both reach wider.their maximum height. The rate of In boys, the muscles of the body growgrowth in height varies in different more prominently than in the girls.individuals. Some may grow suddenly Thus, changes occurring in adolescentat 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 throatREACHING THE AGE OF ADOLESCENCE 115
  4. 4. called Adam’s apple (Fig. 10.2). In girls, and pimples on the face at this timethe larynx is hardly visible from the because of the increased activity of theseoutside 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 Organsadolescent boys, sometimes, the muscles Look up Fig. 9.1 and 9.3 of theof the growing voice box go out of control previous lesson which shows sexand the voice becomes hoarse. This state organs of humans. At puberty, malemay remain for a few days or weeks after sex organs like the testes and peniswhich the voice becomes normal. develop completely. The testes also begin to produce sperms. In girls, the ovaries enlarge and eggs begin to Adam’s mature. Also ovaries start releasing apple mature eggs. Reaching Mental, Intellectual and Emotional Maturity Adolescence is also a period of change in a person’s way of thinking. Adolescents are more independent than before and are also self conscious. Intellectual development takes place and they tend to spend considerable time Fig. 10.2 : Adam’s apple in a grown up boy thinking. In fact, it is often the time in one’s 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 knowIncreased Activity of Sweat and that there is no reason to feel insecure.Sebaceous Glands These changes are a natural part ofDuring 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 puberty116 SCIENCE
  5. 5. and boys begin to grow facial hair, that The testes and ovaries secrete sexis, moustaches and beard. As these hormones. You have just learnt thatfeatures help to distinguish the male these hormones are responsible for thefrom the female they are called male and female secondary sexualsecondary sexual characters. Boys characters. Further, the sex hormonesalso develop hair on their chest. In are under the control of hormones fromboth, boys and girls, hair grows under the pituitary gland (Fig. 10.3). Thethe arms and in the region above the pituitary secretes many hormones, onethighs 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 atadolescence are controlled byhormones. Hormones are chemicalsubstances. These are secretions fromendocrine glands, or endocrine system.The male hormone or testosteronebegins to be released by the testes atthe onset of puberty. This causeschanges in boys about which you havejust learnt, for example, the growth offacial hair. Once puberty is reached ingirls, ovaries begin to produce the femalehormone or estrogen which makes thebreasts develop. Milk secreting glandsor mammary glands develop inside thebreasts. The production of thesehormones is under the control ofanother hormone secreted from anendocrine gland called pituitary gland. Fig. 10.3 : The onset of puberty is controlled by10.4 Role of Hormones in hormones Initiating Reproductive Function Paheli and Boojho have nowEndocrine glands release hormones understood that puberty marks theinto the bloodstream to reach a beginning of the reproductive periodparticular body part called target site. when one becomes capable ofThe target site responds to the reproduction. But they want to knowhormone. 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
  6. 6. 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 itsreproduction when their testes and breakdown if pregnancy does notovaries begin to produce gametes. The occur. In case the egg is fertilised itcapacity for maturation and production begins to divide and then getsof gametes lasts for a much longer time embedded in the uterus for furtherin 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 ofage) and generally lasts till the age of 10.6 How is the Sex of theapproximately 45 to 50 years. The ova Baby Determined?begin to mature with the onset ofpuberty. One ovum matures and isreleased by one of the ovaries once inabout 28 to 30 days. During this I heard my mother and myperiod, the wall of the uterus becomes aunt talking about my cousinthick 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 whetherThis results in pregnancy. If she would give birth to a boyfertilisation does not occur, the or a girl. I wonder what makesreleased egg, and the thickened lining the fertilised egg develop either into a boy or a girl!of the uterus along with its bloodvessels are shed off. This causes Boy or Girl?bleeding in women which is calledmenstruation. Menstruation occurs Inside the fertilised egg or zygote is theonce in about 28 to 30 days. The first instruction for determining the sex ofmenstrual flow begins at puberty and the baby. This instruction is present inis termed menarche. At 45 to 50 years the thread-like structures, calledof age, the menstrual cycle stops. chromosomes in the fertilised egg.Stoppage of menstruation is termed Recall from Chapter 8, thatmenopause. Initially, menstrual cycle chromosomes are present inside themay be irregular. It take some time to nucleus of every cell. All human beingsbecome 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. But118 SCIENCE
  7. 7. 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 thehas 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 testesegg, the zygote would have two X and the ovaries, there are otherchromosomes and develop into a female endocrine glands in the body such aschild. If the sperm contributes a Y thyroid, pancreas and adrenalschromosome to the egg (ovum) at (Fig. 10.5).fertilisation, the zygote would developinto 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 sexchromosomes of the father determine the Fig. 10.5 : Position of endocrine glands in thesex of an unborn baby. The belief that human bodythe mother is responsible for the sex of Boojho and Paheli had once visitedher baby is completely wrong and to their aunt who was a doctor andblame her for this is totally unjustified. remembered that a boy named Kaka had10.7 Hormones other than a very big and bulging throat. Their aunt had told them that Kaka was suffering Sex Hormones from ‘goitre’, a disease of the thyroidLook at Fig. 10.3 again. The hormones gland. Kaka’s thyroid gland was notsecreted by the pituitary stimulate testes producing the hormone thyroxine.REACHING THE AGE OF ADOLESCENCE 119
  8. 8. Their aunt also told them that their This change from larva to adult isuncle was suffering from ‘diabetes’ called metamorphosis (Fig. 9.10).because his pancreas was not producing Metamorphosis in insects is controlledthe hormone insulin in sufficient by insect hormones. In a frog, it isquantities. Boojho and Paheli then controlled by thyroxine, the hormoneasked their aunt about the adrenal produced by thyroid. Thyroxineglands, which are also shown in the production requires the presence ofchart hung on the wall of her clinic. The iodine in water. If the water in whichaunt told them that adrenal glands the tadpoles are growing does notsecrete hormones which maintain the contain sufficient iodine, the tadpolescorrect salt balance in the blood. cannot become adults.Adrenals also produce the hormoneadrenalin. It helps the body to adjustto stress when one is very angry, If people do not haveembarrassed or worried. enough iodine in their diet, Thyroid and adrenals secrete their will they get goitre causedhormones when they receive orders from by lack of thyroxine?the pituitary through its hormones.Pituitary also secretes growth hormone Activity 10.3which is necessary for the normalgrowth of a person. Collect information from magazines or from doctors and prepare a note on the importance of consuming iodised salt. You can also look for this information on the internet. Are there hormones in other animals also? Have they any role to play in 10.9 Reproductive Health reproduction? The physical and mental well being of an individual is regarded as an10.8 Role of Hormones in individual’s health. To keep the body healthy, every human being, at any age, completing the Life needs to have a balanced diet. The History of Insects and person must also observe personal Frogs hygiene and undertake adequateYou have already learnt about the life physical exercise.history of the silk moth and the frog. During adolescence, however, theseThe caterpillar has to pass through become even more essential as the bodyvarious stages to become an adult moth. is growing.Recall from Class VII the stages of thelife history of the silk moth. Similarly, Nutritional Needs of the Adolescentsthe tadpole passes through certain Adolescence is a stage of rapid growthstages to become a frog (Chapter 9). and development. Hence the diet for an120 SCIENCE
  9. 9. adolescent has to be carefully planned. Activity 10.5You have already learnt what a balanced Get ideas from the pictures given indiet is. Recall that a balanced diet means Fig.10.6. Prepare charts or postersthat the meals include proteins, and paste them in the class so thatcarbohydrates, fats and vitamins in you are aware of the diet forrequisite proportions. Our Indian meal adolescents. You may use yourof roti/rice, dal (pulses) and vegetables creative ideas and present it like anis a balanced meal. Milk is a balanced advertisement. You may evenfood in itself. Fruits also provide organise a competition on this topic.nourishment. For infants, mother’s milkprovides all the nourishment that theyneed. Iron builds blood and iron-rich food meatsuch as leafy vegetables, jaggery, meat, vegetablescitrus, Indian gooseberry (amla) are goodfor adolescents. milk and Check items for lunch and dinner in eggsyour meal. Is the meal balanced andnutritious? Does it include cerealswhich give energy and milk, meat, nutsand pulses which provide proteins forgrowth? Also, does it include fats and fruitssugar that give energy? What aboutfruits and vegetables which areprotective foods? Chips and packed ortinned snacks, though very tastyshould never replace regular meals asthey do not have adequate nutritionalvalue. grainsActivity 10.4 Fig. 10.6 : Nutritious items of food Make a group with your friends. Write down the items of food in your Personal Hygiene breakfast, lunch and dinner you Everyone should have a bath at least had on the previous day. Identify once everyday. It is more necessary for the items responsible for proper teenagers because the increased activity growth. Also identified the junk of sweat glands sometimes makes the food that you consumed the body smelly. All parts of the body should previous day. be washed and cleaned everyday. IfREACHING THE AGE OF ADOLESCENCE 121
  10. 10. cleanliness is not maintained there are Activity 10.6chances of catching bacterial infection.Girls should take special care of Collect data on the number ofcleanliness during the time of menstrual children in your class who exerciseflow. They should keep track of their regularly and who do not exercisemenstrual cycle and be prepared for the regularly. Did you notice anyonset of menstruation. difference in their fitness and health? Prepare a report on thePhysical exercise benefits of regular exercise.Walking and playing in fresh air keepsthe body fit and healthy. All young boys Say “NO” to Drugsand girls should take walks, exercise Adolescence is a period of muchand play outdoor games. activity in the body and mind which is a normal part of growing up. So do Myths, Taboos, Do’s and Don’ts not feel confused or insecure. If You have lear nt here and from anybody suggests that you will get Chapter 9 the scientific facts related relief if you take some drugs, just say to human reproduction. There are ‘No’ unless prescribed by the doctor. many wrong notions which you should Drugs are addictive. If you take them now be able to discard as informed adolescents. For example, there are once, you feel like taking them again myths and taboos regarding bodily and again. They harm the body in the changes that adolescents experience. long run. They ruin health and Some of these are given below and happiness. you can now argue why these are You must have heard about AIDS myths and not facts. which is caused by a dangerous virus, 1. A girl becomes pregnant if HIV. This virus can pass on to a she looks at boys during normal person from an infected menstruation. 2. The mother is responsible for the person by sharing the syringes used sex of her child. for injecting drugs. It can also be 3. A girl should not be allowed to transmitted to an infant from the work in the kitchen during infected mother through her milk. The menstruation. virus can also be transmitted through You may come across many other myths sexual contact with a person infected and taboos. Discard them. with HIV. Adolescent Pregnancy You might be knowing that in our country, 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. It also curtails employment opportunities for the young woman and may cause mental agony as she is not ready for responsibilities of motherhood.122 SCIENCE
  11. 11. KEYWORDS WHAT YOU HAVE LEARNT ADAM’S APPLE Humans become capable of reproduction af- ADOLESCENCE ter puberty sets in. Between the ages of 11 years and 19 years children are called ado- ADRENALIN lescents. The onset of puberty brings about growth of BALANCED DIET the reproductive organs. Hair grow at various ENDOCRINE GLANDS places on the body. Breasts develop in girls and facial hair (moustache and beard) appear ESTROGEN in boys. Voice of boys becomes hoarse as voice HORMONES box enlarges during adolescence. Children gain height during adolescence. INSULIN The onset of puberty and maturity of PITUITARY GLAND reproductive parts are controlled by hormones. Hormones are secretions of endocrine glands PUBERTY which pour them directly into the blood stream. REPRODUCTIVE Pituitary gland secretes hormones which in- HEALTH clude growth hormone and hormones that make other glands such as the testes, ovaries, SECONDARY SEXUAL thyroids and adrenals, secrete hormones. CHARACTERS Pancreas secretes insulin, thyroid produces SEX CHROMOSOMES thyroxine and adrenals produce adrenalin. Testosterone is the male hormone and TARGET SITE estrogen, the female hormone. The uterine wall in females prepares itself to receive the TESTOSTERONE developing fertilised egg. In case there is no THYROXINE fertilisation, the thickened lining of the uterine wall breaks down and goes out of the body VOICE BOX along with blood. This is called menstruation. Sex of the unborn child depends on whether the zygote has XX or XY chromosomes. It is important to eat balanced food and maintain personal hygiene during adolescence.REACHING THE AGE OF ADOLESCENCE 123
  12. 12. Exercises 1. What is the term used for secretions of endocrine glands responsible for changes taking place in the body? 2. Define adolescence. 3. What is menstruation? Explain. 4. List changes in the body that take place at puberty. 5. Prepare a Table having two columns depicting names of endocrine glands and hormones secreted by them. 6. What are sex hormones? Why are they named so? State their function. 7. Choose the correct option. (a) Adolescents should be careful about what they eat, because (i) proper diet develops their brains. (ii) proper diet is needed for the rapid growth taking place in their body. (iii) adolescents feel hungry all the time. (iv) taste buds are well developed in teenagers. (b) Reproductive age in women starts when their (i) menstruation starts. (ii) breasts start developing. (iii) body weight increases. (iv) height increases. (c) The right meal for adolescents consists of (i) chips, noodles, coke. (ii) chapati, dal, vegetables. (iii) rice, noodles and burger. (iv) vegetable cutlets, chips and lemon drink. 8. Write notes on— (a) Adam’s apple. (b) Secondary sexual characters. (c) Sex determination in the unborn baby.124 SCIENCE
  13. 13. 9. Word game : Use the clues to work out the words. EXERCISES 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. Voice box 7. Term for changes at adolescenceREACHING THE AGE OF ADOLESCENCE 125
  14. 14. 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? Age Height (cm) (Years) Boys Girls 0 53 53 4 96 92 8 114 110 12 129 133 16 150 150 20 173 165 Extended Learning — Activities and Projects 1. Find out from your elder relatives about their awareness of the legal status of early marriage. You yourself may get information on it from your teacher, parents, a doctor or the internet. Write a two- minute speech explaining why early marriage is not good for the couple. 2. Collect newspaper cuttings and information in magazines about HIV/ AIDS. Write a one page article of 15 to 20 sentences on HIV/AIDS. 3. In our country, according to a census, there are 882 adolescent females for every 1000 males. Find out. (a) the concerns of the community regarding this low ratio. Remember that the chance of having a boy or a girl is equal. (b) what amniocentesis is and how useful this technique is. Why is its use for identification of sex of the unborn child banned in India? 4. Put your ideas together and write a short note on the importance of knowing facts about reproduction. For more information, visit : www.teenshealth.org/teen/sexual_health/ www.ama_assn.org/ama/pub/category/1947.html www.adolescenthealth.com126 SCIENCE

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