Prenatal Development

Prenatal Development

1. Week 3 to week 8

   • Embryonic stage
     • one implantation has occurred Organism is now known as the embryo
       • 2cm in length
     • Cell Differentiation
       • Cells take on specialised roles
         • Heart Cells
         • Skin Cells
     • Most critical stage for human development
       • begins to develop all major organs
         • Brain
         • Spinal Cord
         • Heart
         • By the end of this stage, all major organs are present and will continue to develop
     • Sex cells begin to develop
       • Cannot determine if male/female yet
     • Limbs start to bud
       • Eventually form fingers and toes
     • By week 8, 90% of structures found in an adult human can be identified
       • starts to look human looking
       • Head and neck account for half the total length
       • Brain makes up half of its body weight
     • sensitive during this stage to environmental influences
       • Teratogens
         • Tobacco
         • Alcohol
         • Medication

2. Week 8 to Week 40/birth

   • Foetal Stage
     • Embryo is now known as foetus
     • Characterised by Rapid growth
       • Measures only a few cm long at beginning
         • Ends stage at 50cm
     • Systems begin to function
       • Lungs
       • Digestive system
       • Liver
       • Kidneys
     • Sex organs start taking shape by week 15.
       • Identify Sex by ultrasound
       • Female
         • Produces millions of eggs
       • Male
         • Testes produce testosterone
     • Movement and reflexes occurs
       • Sucking
       • Grasping
     • Breathing movements occur
       • No air but amniotic fluid
     • Bones Harden
       • Tooth buds form in gums
     • Senses begin to function
       • Sound
       • Light
       • Touch
     • Fat is deposited under skin
       • Assists with temperature after birth

3. Conception to week 2

   • Germinal Stage
     • Zygote
       • Forms when a sperm and ova meet
       • Travels down the fallopian tube and constantly divides
     • Morula
       • At approx. 16 cells (day 3-4) starts to form a spherical shape
     • Blastocyst
       • At approx. 64 cells (day 5) begins to form a hollow fluid centre, an inner mass and an outer mass
         • Inner cell becomes embryo
         • Outer cell becomes placenta
       • At approx. day 7/8 blastocyst attaches to the wall of the uterus
         • Fully implanted by day 11-15

4. Placenta

   • Formed and fully functioning in embryonic stage
   • Disc Shaped
   • Temporary organ
     • Acts as kidney, lung and digestive system for the foetus
       • Supplies oxygen
       • Delivers nutrients and hormones
       • Removes waste (urine and carbon dioxide
       • Provides Immune Support
   • Connected through the foetus through the umbilical cord
     • Made up of two artiries
       • Oxygenated/nutrient rich
       • Deoxygenated/nutrient depleted
     • Exchange of substances between mother and baby occur through thing walls of placenta
   • Produces hormones that helps maintain pregnancy

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