PregnancyPregnancyPregnancyPregnancyObjectives:

What happens to an egg after fertilisation?How does a baby develop in the uterus?What is the role of the placenta?

The The fertilised fertilised eggeggThe fertilised egg moves down the oviductWhen it reaches the uterus it is a ball of cellsIt buries itself in the uterus wall

The The embryoembryoThe ball of cells keeps growing and developing into an embryoNo new eggs are releasedThe uterus keeps its lining to protect the embryo

The The placentaplacentaThe placenta links the embryo and the uterusTo supply food and oxygen and remove wasteThe mother’s blood and the embryo’s blood flow side by side but do not mix

Unfortunately, some drugs and viruses can enter the baby’s blood through the placenta

The placenta acts as a barrier to some harmful substances

The The FoetusFoetusAfter two months the embryo becomes a foetusIt is too big to be attached to the uterus wallIt is connected to the placenta by the umbilical cordAnd protected by bag of fluid called the amnion

•The process from fertilisation to birth takes about thirty eight weeks in humans.

The The BirthBirth

•The process of birth is controlled by hormones. The baby is forced out of the uterus by powerful muscle contractions.

•The baby is breast fed by the mother. All mammals have mammary glands for this purpose.

Questions Questions ??1. How does the uterus protect the

embryo? answer2. Where does oxygen and food pass from

the mother to the embryo?

3. Name two waste materials that pass from the embryo to the mother

placentauterus cervixamnion

Carbon dioxide and oxygen

Carbon dioxide and tobacco smoke

Carbon dioxide and urea

Answer to question 1Answer to question 1Answer to question 1Answer to question 1The thick lining of the uterus provides food and protection for the developing embryo

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3 weeksThe fertilised egg is dividing rapidly. It has formed a ball of cells. It is too small to be seen without a microscope.

12 weeksThe foetus is about 50 mm long. It can kick its legs and move its fingers. Its head is out of proportion with the rest of its body. Most of the organs inside its body are working.

6 weeksThe ball of cells now looks like a tadpole. There is a “head end” and a “tail end” and a bulge where the heart is forming. 

24 weeksThe foetus has grown so much that the mother looks pregnant. She can feel her baby moving inside her. Its heart can be heard beating.

8 weeksYou can now see the eyes. The arms and legs have formed with tiny fingers and toes. At this stage the baby is called a foetus. 

30 weeksThe baby is almost ready to be born. Its head is just about the cervix. When the muscles of the mother’s uterus contract, it will be born head first.

Stages of pregnancyStages of pregnancy

Match the diagrams to the wordsMatch the diagrams to the words

3 weeksThe fertilised egg is dividing rapidly. It has formed a ball of cells. It is too small to be seen without a microscope.

12 weeksThe foetus is about 50 mm long. It can kick its legs and move its fingers. Its head is out of proportion with the rest of its body. Most of the organs inside its body are working.

6 weeksThe ball of cells now looks like a tadpole. There is a “head end” and a “tail end” and a bulge where the heart is forming. 

24 weeksThe foetus has grown so much that the mother looks pregnant. She can feel her baby moving inside her. Its heart can be heard beating.

8 weeksYou can now see the eyes. The arms and legs have formed with tiny fingers and toes. At this stage the baby is called a foetus. 

30 weeksThe baby is almost ready to be born. Its head is just about the cervix. When the muscles of the mother’s uterus contract, it will be born head first.

Stages of pregnancyStages of pregnancy

bite size

placenta

Structure made by an embryo to obtain food and oxygen from its mother _______________

A human embryo after 2 months _____________

The first 2 months of development for a new baby___________

Fluid filled bag that protects the foetus_________

Attaches the embryo to the placenta _______________________

Key wordsKey words

amnion Umbilical cord foetus embryo

placentaStructure made by an embryo to obtain food and oxygen from its mother _______________

A human embryo after 2 months _____________

The first 2 months of development for a new baby___________

Fluid filled bag that protects the foetus_________

Attaches the embryo to the placenta _______________________

Key wordsKey words

amnion

Umbilical cord

foetus

embryo