The Development of the Embryo through to Birth

Unit 4

Conception

• How does conception happen?

• http://www.youtube.com/watch?v=9CO5Nl_ngCo

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

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

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

4 Weeks

• The embryo produces hormones which stop the mother’s menstrual cycle

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.• http://pregnancy.about.com/od/pregnancycalendar/i

g/Early-Ultrasound-Photos/

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

• http://pregnancy.about.com/od/pregnancycalendar/ig/6-Weeks-Pregnant.-Tgk/

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• http://pregnancy.about.com/

od/pregnancycalendar/ig/8-Week-Ultrasound-Photos/

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• http://pregnancy.about.com/od/pregnancycalendar/i

g/10-Week-Ultrasound-Photos/

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

14 Weeks

• Muscles lengthen and become organised

• Mother will soon start feeling first flutters of the feotus kicking and moving

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• http://pregnancy.about.com/od/pregnancycalendar/i

g/16-Week-Ultrasound-Photos/

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?• http://video.about.com/preg

nancy/Ultrasound.htm• Ultrasound device can tell if

girl or boy and pick up certain abnormalities such as Spina Bifida, Cleft Lip/Palate etc.

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

• http://pregnancy.about.com/od/pregnancycalendar/ig/24-Week-Ultrasound-Photos/

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

• http://pregnancy.about.com/od/pregnancycalendar/ig/30-Week-Ultrasound-Photos/

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

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

40 Weeks

• Now approx 7 & a half pounds• Is ready for life outside its womb• Vaginal Delivery:• http://video.about.com/pregnancy/Delivery.

htm• Caesarean• http://video.about.com/pregnancy/Cesarea

n-Section.htm• Real Life C-Section• http://www.babycenter.ca/video/pregnancy

/c-section/• http://www.mayoclinic.com/health/c-sectio

n/MM00531• 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.