Unit 3: Reproduction

Unit 3: REPRODUCTION

0. INTRODUCTION

Humans, like many living things, reproduce by sexual reproduction. Reproductive cells in male humans are called sperm while in females they are called ova. When they meet, they produce a zygote which eventually becomes an embryo, which turns into a foetus and then finally into a baby! However, humans, like most animals, have to reach sexual maturity before they can reproduce. This happens in adolescence – the stage between childhood and being an adult. What do we call this process?

1. THE FEMALE REPRODUCTIVE SYSTEM

OVA:
The female reproductive cells are called ova. The ovaries produce the female reproductive cells.

FEMALE REPRODUCTIVE ORGANS:
Most of the female reproductive organs are internal. They are located in the lower abdomen.

1. Ovaries
The ovaries produce female reproductive cells called ova. 
One ovum matures each month. Women are born with all the ova they will need for the rest of their life.

2. Fallopian tubes
The fallopian tubes connect the ovaries to the uterus.

3. Uterus
The uterus is an organ with muscular walls. During pregnancy a fertilised cell develops into a baby in the uterus. The part of the uterus that leads to the vagina is called the cervix.

4. Vagina
The vagina is a muscular tube which connects the uterus to the outside of the body. The vulva is on the outside of the body and covers the opening to the vagina.

MINDMAP TIME!

2. MALE REPRODUCTIVE SYSTEM

SPERM:
The male reproductive system produces and transports sperm cells. A sperm cell has an oval shape and a tail. The tail allows it to move up the female’s fallopian tubes and fertilise the ovum. Men produce millions of sperm every day.

MALE REPRODUCTIVE ORGANS:
Most male reproductive organs are external and are located on the outside of the body.

- The testicles produce and store sperm. The testicles are located in a bag of skin called the scrotum. The scrotum regulates the temperature of the testicles. They need to be a bit cooler than the rest of the body in order to produce sperm.

- Sperm travels through two tubes called the vasa deferentia to the seminal vesicles. The seminal vesicles produce a liquid that forms part of semen.

- The prostate produces a liquid that also forms part of semen. Semen carries the sperm and gives it nutrients.

- The penis contains the urethra. The sperm travels through the urethra to the outside of the body. The urethra also expels urine.

MINDMAP TIME!

VIDEO TIME!

3. Festilisation, pregnancy and birth.

Human reproduction involves two different sex cells: a female ovum and a male sperm. Each cell carries different genetic information which is why children are unique; they have genetic code from both parents. Male and female reproductive systems are different: the male’s is designed to produce and deliver sperm, while the female’s is designed to produce ova, as well as housing, nourishing and protecting a developing foetus.

1. Fertilisation
Fertilisation of the ovum can occur after the egg is released into the fallopian tubes. During sexual intercourse the man’s penis is inserted into the woman’s vagina, and the sperm are deposited there. Then, using their tails they swim up the vagina to the ovum in the fallopian tube. Only one sperm can fertilise an ovum. Once the ovum is fertilised, the cells will start to divide and multiply. This ball of cells is called a zygote.

2. Development of the embryo

After fertilisation, the zygote travels to the uterus where its cells carry on dividing and multiplying until they become an embryo. The embryo fixes itself onto the lining of the uterus where it will continue to grow. At eight weeks, the embryo is about the size of an adult’s thumb.

3. Development of the foetus
After about nine weeks, all the organs have formed and the embryo develops into a foetus. The foetus floats in a sac of amniotic fluid which protects it from knocks and bumps. The foetus receives oxygen and nourishment from the mother’s placenta. Waste matter and carbon dioxide are transferred from the foetus to the mother via the placenta. The baby is connected to the placenta by the umbilical cord.

4. Birth

Pregnancy lasts about 280 days. When the foetus is ready to be born, it pushes against the cervix, which starts to open and widen. Amniotic fluid is released which is often the first sign that birth is about to start. The muscles of the uterus begin to contract and the cervix opens sufficiently to allow the foetus, now a baby, to pass. The baby is pushed through the cervix and along the birth canal. Babies are usually born head first. The umbilical cord comes out with the baby. This is cut and tied, and forms our navel or belly button. The placenta or afterbirth comes out after the baby.