Human reproduction

1

SCIENCE 6.

UNIT 3. HUMAN REPRODUCTION.

CONTENTS: 1.– Changes on the body. Puberty: Secondary sex characteristics.

2.– Male reproductive system.

3.– Female reproductive system.

4.– Reproductive cells. Male cells—Female cells. Menstrual cycle.

5.– Fertilisation and pregnancy.

6.– Childbirth.

Reproduction is one of the vital function that living beings do.

All living beings can produce more beings similar to themselves, so human beings can also produce more human beings similar to them.

In nature, there are two kinds of reproduction: asexual reproduction and sexual reproduction. a.– Asexual reproduction: when only one individual produces new living beings on its own (descendents). The new living being inherits only the genes from that parent. b.– Sexual reproduction: when a male and a female produce new living beings. The new living being inherits genes from both, its mother and its father.

1.– CHANGES ON THE BODY IN PUBERTY: SECONDARY SEXUAL CHARACTERISTICS. Before the moment a baby is born, reproductive organs of boys and girls are different. These differences from males and females are called primary sexual characteristics.

C.E.I.P. SANTA ANA (Madridejos)

HUMAN REPRODUCTION is the process in which human beings produce more human beings similar to themselves.

Human reproduction is sexual. A male and a female produce a new baby.

On a baby, you can distinguish his/her primary sexual characteristics: his/her reproductive organs.

Secondary sexual characteristics are features that distinguish the two sexes, but that are not directly part of the reproductive system.

Secondary sexual characteristics are changes in boys and girls during the adolescence or puberty.

Puberty is a period of time when a child’s body changes into an adult body (from 11 to 18 year for girls, and from 13 till 18 for boys ). There are physical and psychological changes, and its reproductive system reach maturity.

Sexual glands produce hormones. Males produce testosterone and females oestrogen that control these changes.

Boys and girls:

.- Appearance of pubic and armpit hair for boys and girls.

Boys: .- Adam’s apple is visible and voice gets lower. .– Shoulders get broader and muscle development. .– Hair on the face, body, arms and legs appears. .- Testicles mature and produce sperm.

MALE

Facial hair

Adam’s apple

Broad shoulders armpit

Girls: .– Breasts development. .– Hips widen. .– The first menstrual cycle comes.

FEMALE Breasts development

Increase of hair on body, arms and legs Pubic hair

Mature genital organs Muscle development

1 Widen hips

Pubic hair

USEFUL WORDS: .– sexual reproduction .– asexual reproduction .– primary sexual characteristics .– secondary sexual characteristics .– adolescence .– puberty .– hormones

2 C.E.I.P. SANTA ANA (Madridejos)

2.– MALE REPRODUCTIVE SYSTEM. Male reproductive system produces male’s reproductive cells (sperm).

It produces millions of sperm a day.

Bladder

Bladder

3.- Seminal vesicles are two glands next to the bladder. They produce seminal fluid that mixes with the sperm.

2

6

1

4.- Prostate gland is a gland under the bladder. It produces prostate fluid that mixes with the sperm.

5.- Urethra is a tube that connects vas deferens and bladder to the exterior.

Sperm or urine travel through the urethra to the exterior.

2.- Vas deferens are two tubes from testicles to seminal vesicles.

Sperm travels through them.

1.- Testicles or testes are two small round organs placed outside the abdominal cavity. They are covered by skin called scrotum.

They produce millions of sperm a day.

6.- Penis is a cylindrical organ that contains the urethra.

Scrotum

2

3.– FEMALE REPRODUCTIVE SYSTEM. Female reproductive system has got two functions: A.– It produces female’s reproductive cells (egg cell or ovum).

B.– It protects and feeds the new human being (embryo) till the birth.

1.- Ovaries are two organs (the size of an almond).

They produce and develop egg cells.

Ovaries release an egg a month through the Fallopian tubes.

3

2.– Fallopian tubes or oviducts are two tubes that connect the ovaries to the uterus.

3.– Uterus or womb is a cavity with thick muscular walls. It contains the embryo during the nine months of pregnancy.

Muscular walls of uterus.

2

Cervix is the lower part of the uterus.

4

1

4.– Vagina is a muscular tube that connects the uterus with the outside of the body.

3 4

5

5.– Vulva is the external organ in the female reproductive system, that protects the entrance to the vagina.

5

.– testicles .– prostate .– ovaries .– vagina

.– vas deferens .– seminal vesicles .-urethra .– penis .– uterus .– fallopian tubes .– vulva

3 C.E.I.P. SANTA ANA (Madridejos)

4.– REPRODUCTIVE CELLS. Human beings have sexual reproduction. Male individuals produce male sex cells (sperm) and female individuals produce female sex cells (egg cell or ovum). Each sex cells have got genetic information, so new offspring will have some characteristics from the father and others from the mother.

Midpiece 4.1.– SPERM (male sex cell).

Testicles produce millions of sperm a day, but they only can live for a few hours.

They are very small and they are formed by three parts: .– Head that contains the nucleus with the genetic information.

Sperm .– Midpiece Head Tail .– Tail to move very fast looking for the egg cell.

4.2.– EGG CELL or OVUM (female sex cell).

Girls have all their female reproductive cells in follicles in their ovaries from they were born. From puberty, one these eggs matures and is released every month.

It’s round and much bigger than sperm.

It has got a nucleus with the genetic information.

It hasn’t got active movement.

Egg cell under a microscope

4.3.– MENSTRUAL CYCLE. About every 28 days, one ovary releases an egg that is called ovulation. An egg lives only during 24 - 48 hours.

The uterus walls are thickening to prepare to develop the egg just in case the egg is fertilised.

If the egg is not fertilised, it will die and it will be expelled with the rest of the uterus lining (menstruation or period). When menstruation begins, it is important to have a good hygiene.

4.-Preparation of the uterus: The uterus lining continues to thicken.

The egg moves into the uterus.

If the egg is unfertilized, the uterus lining breaks down.

1.- Menstruation: The unfertilised egg and the mucosal tissue with blood vessels from uterus are expelled. (about 1st - 6th days)

6

Egg released

Ovary

Follicle

3.- Ovulation: The follicle releases an egg. It falls down through the Fallopian tube to the uterus.

(Fertile time)

2.- Preparation of the egg: A follicle in an ovary matures an egg.

Uterus lining starts to grow and thick again

7

4 C.E.I.P. SANTA ANA (Madridejos)

5.A.– FERTILISATION. When the man deposits millions of sperm in the woman’s vagina, many of them move up the vagina, into the uterus and finally into the Fallopian tubes. If they find an egg, they will try to get inside, but only one sperm will enter. This process is called fertilization, and the fertilised egg becomes a zygote (the first cell of the embryo) 1.– The egg is released from the ovary and goes down through the Fallopian tube to the uterus.

2.– Sperm enter through the vagina, and travels to the Fallopian tube.

3.– Lots of sperm get the egg, but only one will enter and a zygote is formed

4.– The zygote divides and forms an embryo.

Fertilisation is the fusion of a sperm with an ovum to produce a new organism.

Zygote is the first cell of the embryo.

8

5.– The embryo implants on the uterus wall to grow and develop.

5.B.– PREGNANCY. Pregnancy is the time the embryo/foetus Pregnancy lasts for about nine months (38 - 40 weeks) and finishes is developing inside the mother’s uterus. in childbirth.

The embryo is developing, and brain, heart, arms and other organs are formed. After 8 weeks, it’s called foetus.

At the beginning, placenta, umbilical cord and amniotic sac are formed. After the 4 th month the fetus can hear, open the eyes, move inside… During last three months, the fetus grows and the organs mature.

Placenta is an organ formed on the wall of the uterus and supplies nutrients, oxygen… from the mother’s blood.

Amniotic sac is a bag with liquid inside (amniotic fluid) to protect the fetus.

It’s formed at the same time as the placenta

9

10

11 Umbilical cord links the placenta to the fetus. It contains arteries and veins to transport blood with oxygen, nutrients...

12

USEFUL WORDS: .– fertilisation .– egg .– sperm .– zygote .– embryo .- fetus / foetus .– placenta .– umbilical cord .– amniotic sac .– amniotic fluid

5 C.E.I.P. SANTA ANA (Madridejos)

6.– CHILDBIRTH. About 9th month of pregnancy, the fetus is totally mature and ready to be born. It’s about 50cm high and weights about 3,3 kg. It’s time for labor or childbirth.

Normally, baby’s head goes out first. But sometimes, the fetus is upside-down and he/she can’t go out, so the doctor has to make a surgical operation called caesarean birth.

Labor has got three stages: .– Dilation .– Expulsion .– Placenta delivery

1.- Dilation: 6 - 12 hours (or more in first child). It begins with regular uterine contractions and ends with full dilation of the cervix (about 10cm)

2.– Expulsion: the fetus is pushed out through the vagina by the contractions of the uterus.

When the fetus comes out the doctor cuts the umbilical cord (its scar is the navel).

After a few seconds, the baby starts to cry and breath.

13

3.– Placenta delivery: is the last stage of the labor. Contractions of the uterus expel the placenta and the rest of tissues.

15

USEFUL WORDS: .– labor or childbirth .– dilation .– expulsion

14

.- caesarean birth .– placenta delivery