REACHING THE A OF ADOLESCENCE I

1 In the previous chapter, you havelearnt how animals reproduce. It isonly after growing up to a certainage that human beings and many otheranimals can reproduce. Why canhumans reproduce only after a certainage?In this chapter, you will learn aboutchanges that take place in the humanbody after which a person becomescapable of Chapter 9, you have learnt abouthuman reproductive organs. Here, weshall discuss the role that hormones playin bringing about changes that make achild grow into an and PubertyBoojho was celebrating his 12thbirthday. After his friends left, Boojhoand Paheli began chatting with theirparents. Paheli studies in an all-girlsschool. She started laughing. Sheremarked that many of Boojho s schoolfriends, whom she met after a year, hadsuddenly shot up in height. Some ofthem were looking very funny with ahairy line above their lips. Her motherexplained that the boys had grown begins from the day one isborn.

2 But upon crossing the age of 10or 11, there is a sudden spurt in growthwhich becomes noticeable. The changestaking place in the body are part ofgrowing up. They indicate that you areI wonder how long thisperiod marked by changesin the body will last!no longer a child but are on the way tobecoming an is a strange period of lifewhen you are neither a child noran adult. I wonder whether thisperiod between childhood andadulthood had a special name!Growing up is a natural process. Theperiod of life, when the body undergoeschanges, leading to reproductivematurity, is called begins around the age of11 and lasts upto 18 or 19 years of this period covers the teens (13to 18 or 19 years of age), adolescentsare also called teenagers . In girls, ADOLESCENCE may begin a year or twoearlier than in boys. Also, the period ofadolescence varies from person to human body undergoes severalchanges during ADOLESCENCE .

3 Thesechanges mark the onset of puberty. Themost important change which markspuberty is that boys and girls becomecapable of reproduction. Puberty endswhen an adolescent reaches THE AGE OF ADOLESCENCEREACHING THE AGE OF ADOLESCENCE2021 22 SCIENCE114% of full heightBoysGirls872%77%975%81%1078%84%118 1%88%1284%91%1388%95%1492%98%1595%99%169 8% inYearsPaheli and Boojhorealised that suddenincrease in height andhairy line above the lipsin boys were signs ofadolescence. Theywanted to know moreabout other changes at PubertyIncrease in HeightThe most conspicuous change duringpuberty is the sudden increase inheight. At this time the long bones, thatis, the bones of the arms and the legselongate and make a person following chart gives theaverage rate of growth in height ofboys and girls with age. The figuresin columns 2 and 3, give thepercentage of the height a personhas reached at the age given incolumn 1.

4 For example, by the age11, a boy has reached 81% of hisprobable full height, while a girlhas reached 88% of her fullheight. These figures are onlyrepresentative and there may beindividual the Table for your friendsand work out how tall they are likelyto be. Find out who is likely to beCalculation for full height (cm)( )100 Present height cm% of full height at this age (as given in the chart)Example:A boy is 9 years old and 120 cmtall. At the end of the growth periodhe is likely to be 12010075 cm = 160 cm tallthe tallest and who might be theshortest in your 22 REACHING THE AGE OF ADOLESCENCE115 There is no need for Paheli to parts of the body do not grow at thesame rate. Sometimes the arms and legsor hands and feet of adolescents lookoversized and out of proportion with thebody. But soon the other parts catchup and result in a proportionate must have noticed that heightof an individual is more or less similarto that of some family member.

5 This isbecause height depends on the genesinherited from parents. It is, however,very important to eat the right kind offood during these growing years. Thishelps the bones, muscles and otherparts of the body get adequatenourishment for growth. You will findnutritional needs of adolescentsdiscussed later in the in Body ShapeHave you noticed that boys in your classhave broader shoulders and wider cheststhan boys in junior classes? This isbecause they have entered the age ofpuberty when shoulders generallybroaden as a result of growth. In girls,the region below the waist boys, the muscles of the body growmore prominently than in the , changes occurring in adolescentboys and girls are ChangeDid you notice that sometimes the voiceof some of the boys in your class cracks?At puberty, the voice box or the larynxbegins to grow. Boys develop larger voiceboxes.

6 The growing voice box in boys canbe seen as a protruding part of the throatActivity the data given in Activity draw a graph. Take age on the X-axis and per cent growth in heighton the Y-axis. Highlight the pointrepresenting your age on the out the percentage of heightyou have already reached. Calculatethe height you might eventuallyreach. Tally your graph with the onegiven here (Fig. ).Fig. :Graph showing percentage of heightwith ageI am worried. Though Ihave become taller, myface looks much smallercompared to my , girls grow faster than boysbut by about 18 years of age, both reachtheir maximum height. The rate ofgrowth in height varies in differentindividuals. Some may grow suddenlyat puberty and then slow down, whileothers may grow 22 SCIENCE116and pimples on the face at this timebecause of the increased activity of theseglands in the of Sex OrgansLook up Fig.

7 And of theprevious lesson which show sexorgans of humans. At puberty, malesex organs like the testes and penisdevelop completely. The testes alsobegin to produce sperms. In girls, theovaries enlarge and eggs begin tomature. Also ovaries start releasingmature Mental, Intellectual andEmotional MaturityAdolescence is also a period of changein a person s way of are more independent thanbefore and are also self development takes place andthey tend to spend considerable timethinking. In fact, it is often the time inone s life when the brain has thegreatest capacity for , however, an adolescent mayfeel insecure while trying to adjust tothe changes in the body and mind. Butas adolescent learners, you should knowthat there is no reason to feel changes are a natural part ofgrowing SexualCharactersYou have learnt in Chapter 9, thattestes and ovaries are the reproductiveorgans.

8 They produce the gametes,that is, sperms and ova. In girls,breasts begin to develop at pubertyMany of my classmateshave a hoarse voice. Now Iknow why?Fig. : Adam s apple in a grown up boycalled Adam s apple (Fig. ). In girls,the larynx is hardly visible from theoutside because of its small , girls have a high pitched voice,whereas boys have a deep voice. Inadolescent boys, sometimes, the musclesof the growing voice box go out of controland the voice becomes hoarse. This statemay remain for a few days or weeks afterwhich the voice becomes few glands such as sweat glands,oil glands and salivary glands releasetheir secretions through glands release hormonesdirectly into the bloodstream. So, theyare also termed ductless Activity of Sweat andSebaceous GlandsDuring puberty the secretion of sweatglands and sebaceous glands (oil glands)increases. Many young people get acneAdam sapple2021 22 REACHING THE AGE OF ADOLESCENCE117and boys begin to grow facial hair, thatis, moustaches and beard.

9 As thesefeatures help to distinguish the malefrom the female they are calledsecondary sexual characters. Boysalso develop hair on their chest. Inboth, boys and girls, hair grows underthe arms and in the region above thethighs or the pubic and Boojho have nowunderstood that puberty marks thebeginning of the reproductive periodwhen one becomes capable ofreproduction. But they want to knowif reproductive life, once begun,continues, or it ends some testes and ovaries secrete sexhormones. You have just learnt thatthese hormones are responsible for themale and female secondary sexualcharacters. Further, the sex hormonesare under the control of hormones fromthe pituitary gland (Fig. ). Thepituitary secretes many hormones, oneof which makes ova mature in theovaries and sperms form in the Boojho and Paheli wish to knowwhat initiates changes at :The onset of puberty is controlled byhormonesThe changes which occur atadolescence are controlled byhormones.

10 Hormones are chemicalsubstances. These are secretions fromendocrine glands, or endocrine 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 of Hormones inInitiating ReproductiveFunctionEndocrine glands release hormonesinto the bloodstream to reach aparticular body part called target target site responds to thehormone. There are many endocrineglands or ductless glands in the Phase ofLife in HumansAdolescents become capable ofreproduction when their testes andovaries begin to produce gametes.