Growth and Development 1

PUBERTY

Viv Rolfe

• Discuss the age of onset of puberty in males and females

• Development of secondary sexual characteristics at puberty

• Identify the roles of hormones in puberty

Lecture Content

What is Puberty?

•Period of growth and sexual maturitymarking the transition from child to adult.

•Maturation of the secondary sexual characteristics.

How old are girls and boyswhen this typically

happens?

Girls

Stop

Child

Adolescence

AdultEarly Late

Age 10 11 12 13 14 15 16 17 18 19 20

Period of Puberty

Girls Boys

Stop Stop

Child

Adolescence

AdultEarly Late

Age 10 11 12 13 14 15 16 17 18 19 20

Period of Puberty

Physiological ChangesVoice breaks

Body hair

Wet dreams

Behavioural changes

Spots

Sweat

Sperm production

Skeletal growth and muscle

Testicles dropping?

Growth – skeletal, muscle, fat

Menstrual cycle – periods

Breast development

Body hair

Sweat and spots

Voice deepening

Mood swings

Development of Secondary Sexual Characteristics(Tanner’s Stages, 1978)

Stage I Pre-adolescent

Stage II First signs of puberty

Stage III Intermediate stage

Stage IV Intermediate stage

Stage V Adult characteristics

Girls Pubertal Changes

Breast Stage 2

Pubic hair Stage 2 Pubic hair Stage 5

Breast Stage 4Menarche

AGE 8 9 10 11 12 13 14 15 16 17

Boys Pubertal Changes

AGE 8 9 10 11 12 13 14 15 16 17

Genital Stage 2

Genital Stage 4

Pubic hair Stage 2

Pubic hair Stage 5

0

5

10

15

20

25

Age (years)

Hei

ght

gain

(cm

/ y

ear)

Boys

Girls

Rate of change of Height gain

Sources: Malina, 1990, Tanner, 1990, Lindsay et al, 1994, Baumgartner et al, 1986 (cited in Bee, 2000)

Puberty is happening at a much earlier agethese days. Why???

What Hormones Trigger Puberty in Girls?

SIMPSON, H.

Source: Aha! Jokes, http://www.AhaJokes.com/ © www.nlm.nih.gov (National Library of Medicine)

Hypothalamus

Pituitary

Pituitary Gland

GONADOTROPHINRELEASING HORMONE

GnRH

FOLLICLE STIMULATING HORMONELUTEINISING HORMONE

OVARIES RELEASEPROGESTERONE

OESTROGEN

INITIATESPUBERTY

PREPARES BODYFOR PREGNANCY

FSHLH

0

10

20

30

40

50

60

70

80

9 10 11 12 13 14

Age (years)

Oes

trag

en l

evel

s(p

g/1

ml)

Boys

Girls

Changes in Oestragen levels

EstrogensProduced by Graafian follicles or the placenta

Stimulates the development of secondary female characteristics

Matures female reproductive organs

Helps prepare the uterus to receive a fertilized egg and maintain pregnancy.

Hormones of the Ovaries

Progesterone

Produced by the corpus luteum

Acts with estrogen to bring about the menstrual cycle

Helps in the implantation of an embryo in the uterus.

Hormones of the Ovaries

What Hormones Trigger Puberty in Boys?

GONADOTROPHIN

FOLLICLE STIMULATING HORMONELUTEINISING HORMONE

FSHLH

TESTESRELEASE

TESTOSTERONE

INITIATESPUBERTY

0

50

100

150

200

250

300

350

400

9 10 11 12 13 14

Age (years)

Tes

tost

ero

ne

leve

ls(n

g/1

ml)

Changes in testosterone levels

Interstitial cells of testes are hormone-producing

Produce several androgens

Testosterone is the most important androgenResponsible for adult male secondary sex characteristics

Promotes growth and maturation of male reproductive system

Required for sperm cell production

Hormones of the Testes

These hormones surge round the bodycompletely changing it.

How long puberty takes varies betweenindividuals.