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PUBERTY Sec 2 Science

Lecture 2

WHAT IS PUBERTY? A time of active growth in humans

during which the person changes from a child to an adult.

WHAT HAPPENS DURING PUBERTY? The reproductive organs mature:

- testes begin to produce sperms- ovaries begin to release eggs

Reproductive organs produce sex hormones:- Male sex hormone = testosterone- Female sex hormone = oestrogen

WHEN DOES PUBERTY START? Boys: 12 to 14 yrs old Girls: 10 to 12 yrs old

PHYSICAL CHANGES IN MALES DURING PUBERTY Reproductive organs grow larger &

production of sperms begin Body growth – height increase Body becomes more muscular Hair growth on face & body (under

armpits & around reproductive organs) Voice sounds deeper Appetite increases

PHYSICAL CHANGES IN FEMALES DURING PUBERTY Increase in height Breasts grow larger Hips become rounder and wider Hair grows under the armpits &

around reproductive organs Menstruation begins

DEVELOPMENT OF THE OVUM At birth, there are many unripe ova in the

ovaries. At puberty, the eggs ripen at different

times. The egg is released from the ovary when

it is ripe / mature (ovulation). Ovulation takes place once every 28 days. Ovary takes turn to release the egg.

DEVELOPMENT OF THE OVUM The uterus becomes thicker and has

more blood. This prepares the uterus for a baby. The fetus develops in the uterus. During the development of the fetus,

the ovaries stop releasing eggs until the baby is born.

DEATH OF THE OVUM If the egg is not fertilised, it dies. The thick lining of the uterus is not

needed. The dead ovum + blood + uterus

lining comes out of the vagina. This is menstruation or period. It lasts from 3 to 7 days.

WHAT IS THE MENSTRUAL CYCLE ? A repeating cycle which involves

a) ovulation (release of an egg)b) preparation of the uterus for

receiving a fertilized eggc) menstruation

Human menstrual cycle

DURATION OF THE MENSTRUAL CYCLE 28 days (it may vary from 23 to 40

days) How to calculate the length of the

menstrual cycle: number of days from 1st day of menstruation to 1st day of next menstruation.

Menstrual Cycle

Ovulation day = Day 14

Ovulation period =+/-1 day of day 14

Fertile period = +/- 3 days of day 14

THE MENSTRUAL CYCLE At first, menstruation may be

irregular. Ovulation occurs at about the 14th

day.

FERTILE PERIOD = +/- 3 days of day 14 of a 28-day cycle (i.e. day 11-17)

Hormones involved in menstruation: Oestrogen

Oestrogen1. Causes the repair and growth of the uterine lining

Hormones involved in menstruation: ProgesteroneProgesterone1. Maintains the uterine lining by causing it to:

a. thicken furtherb. Be supplied with blood capillaries

2. Inhibits ovulation

menopause Cessation of menstruation View Video

http://www.youtube.com/watch?v=s0nAC7ag3XM

Can a 60 yr old man father a child?

Can a 40 yr old woman give birth to a child?