Put these animals into order of gestation period (how long they are pregnant) -

shortest to longest

Shortest - Longest

What about humans?

21 months

Pregnancy: living in the uterus and embryo development

•See the different stages of embryo development•The role of the placenta

The Embryo

Embryo Development

Embryo DevelopmentIn one of these images the developing baby is called an embryo.

Which one is it?

What name is given to the other five developing babies?

ULTRASOUND PICTURES http://www.youtube.com/watch?v=gfgq7WiHbh4

Development of the foetus

Y7

Fertilization, the joining of the sperm and the egg in the fallopian tube (below) to form a unique human being, occurs.

This is a fertilized egg only thirty hours after conception. Magnified here, it is no larger than the head of a pin. Still rapidly dividing, the developing embryo, called a zygote at this stage, floats down from the fallopian tube and towards the uterus.

WEEK 3-5 The embryo’s tiny heart begins to beat by day twenty-one. Arm and leg buds are visible and the formation of the eyes, lips, and nose has begun. The spinal cord grows faster than the rest of the body giving a tail like appearance which disappears as the embryo continues to grow. The placenta begins to provide nourishment for the embryo.

WEEK 7 Major organs have all begun to form. The embryo has developed its own blood type, unique from the mother’s. Hair follicles and knees and elbows are visible. Facial features are also observable. The eyes have a retina and lens. The major muscle system is developed and the embryo is able to move.

WEEK 8-12 The embryo is reactive to its environment inside the amniotic sac where it swims and moves. Hands and feet can be seen. At the end of week 8, the embryonic period is over and the foetal stage begins.

Weeks 13-16 The brain is fully developed and the foetus can suck, swallow, and make irregular breathing sounds. Foetus can feel pain. Foetal skin is almost transparent. Muscles tissue is lengthening and bones are becoming harder. Liver and organs produce appropriate fluids. Eyebrows and eyelashes appear and the fetus makes active movements including kicks and even somersaults.

Week 20-24 A protective waxy substance called Vernix covers the skin. By birth, most of the vernix will be gone but any that is left is quickly absorbed. Foetus has a hand and footprints and fingerprints are forming. Foetus practices breathing by inhaling amniotic fluid into its developing lungs.

Weeks 25 – 28 Rapid brain development occurs during this period and the nervous system is able to control some bodily functions. The foetus’ eyelids now open and close. At 25 weeks there is a 60% chance of survival if born. Weeks 29 – 32 There is a rapid increase in the amount of body fat the foetus has. Rhythmic breathing occurs, but the lungs are not yet mature. The foetus sleeps 90-95% of the day. At this point there the survival rate is above 95% if the baby is born.

Pregnancy Timeline

• Make a time line for pregnancy by ruling a line across a double page

• Divide it into 40 weeks• Cut and stick pictures and words along the line

to show how the embryo grows and develops

Homework

• Find some pictures of embryos to add to your timeline.

• (2 or 3 more images would be good)

The Placenta

It forms a plate-like structure called the placenta.The umbilical cord joins the foetus to the placenta.In the placenta food and oxygen diffuse from the mothers blood into the blood of the foetus. Carbon dioxide and waste products diffuse from the blood of the foetus to the mothers blood.

How does the embryo get food and oxygen and how does it get rid of waste?

The Placenta

1 alcohol

2 drugs

3 smoking

4 HIV virus

Harmful substance

5 Rubella virus

Match the substance to the effect it may have on a developing baby.

Dangers to foetus

Time (weeks) Foetus length (mm)

1.00 0.15

2.00 0.2

4.00 3

7.00 15

16.00 200

36.00 460

Use the data to draw a graph to show growth of foetus

Blockbusters quiz

http://www.teachers-direct.co.uk/resources/quiz-busters/quiz-busters-

game.aspx?game_id=53453