1. The Development of the Embryo through to Birth
Unit 4

2. Conception How does conception happen?

3. The sperm approaching the egg
Sperm & egg join in the fallopian tube
46 chromosomes combine, which pre-determine all of a person’s physical characteristics

4. Fertilized Ovum 30 hours after conception No larger than a pin head
Rapidly dividing
The fertilized Ovum is called a Zygote
Floats down from the fallopian tube towards the uterus

5. 3 Weeks
Once in the Uterus, the developing embryo, called a Blastocyst, searches for a nice place to implant
It actually burrows beneath the surface of the uterus
The yolk sac produces blood cells during the early weeks of life
It is only one sixth of an inch long
The backbone, spinal column, and nervous system are forming.
The kidneys, liver and intestines are taking shape

6. 4 Weeks
The embryo produces hormones which stop the mother’s menstrual cycle

7. 5 Weeks Embryo is size of a raisin
Day 21 – the heart has begun beating
Neural tube enlarges into 3 parts, soon to become a very complex brain
The placenta begins functioning
The spine and spinal cord grows faster than the rest of the body and gives the appearance of a tail.

8. 6 & 7 Weeks
7 weeks – facial features are visible, including a mouth & tongue
The eyes have a retina & lens
The major muscle system is developed
The embryo practices moving and has its own blood type
The blood cells are produced by the liver now instead of the yolk sac

9. 8 Weeks Embryo now called a foetus Is about half an inch long
Is protected by the amnionic sac, filled with fluid
The foetus swims and moves gracefully
Arms & legs have lengthened
Fingers can be seen
Toes will develop in the next few days
Brain waves can be measured

10. 10 Weeks
Heart is almost completely developed and very much resembles that of a newborn baby
The blood is diverted away from the lungs by an opening of the atrium of the heart and the presence of a bypass valve
The blood is oxygenated through the placenta
20 tiny baby teeth are forming in the gums

11. 12 Weeks Vocal chords are complete
Can and does sometimes cry (silently)
Brain is fully formed
Can feel pain
May suck his/her thumb
Eyelids now cover the eyes, and remain shut until the 7th month to protect the delicate optical nerve fibres

12. 14 Weeks Muscles lengthen and become organised
Mother will soon start feeling first flutters of the feotus kicking and moving

13. 15 & 16 Weeks
15 weeks – The feotus has an adults taste buds and may be able to savour the mother’s meals
16 weeks – 5 and a half inches tall
6 ounces in weight
Eyebrows, eyelashes and fine hair appear
The foetus can grasp with his/her hands, kick, or even somersault

14. 20 Weeks 20 weeks – can hear & recognise mother’s voice
Still small & fragile but growing rapidly
Could possibly survive if born
Finger nails and finger prints appear
Sex organs are visible
What happens during an ultra sound?
Ultrasound device can tell if girl or boy and pick up certain abnormalities such as Spina Bifida, Cleft Lip/Palate etc.

15. 24 Weeks Covered with a fine downy hair called Lanugo
Tender skin is protected by a waxy substance called vernix
At birth- substance may still be on the skin but it will be quickly absorbed
Breathing is practiced by inhaling amnionic fluid into developing lungs

16. 30 Weeks The umbilical cord has been the lifeline to the mother
Nourishment is transferred from the mother’s blood, through the placenta, and into the umbilical cord to the feotus
If mother ingests toxic substances i.e. alcohol/drugs, the baby receives these as well

17. 32 & 36 Weeks 32 weeks – The foetus sleeps 90-95% of the day
Sometimes experiences REM sleep, an indication of dreaming
Summary - Ultrasounds week by week

18. 40 Weeks Now approx 7 & a half pounds
Is ready for life outside its womb
Vaginal Delivery:
Caesarean
Real Life C-Section
At birth the placenta will detach from the side of the uterus.
Umbilical cord will cease working as the first breaths are taken.
Child’s breathing will trigger changes in the structure of the heart and bypass arteries which will force all blood to now travel through the lungs.