A zygote is fertilized cell with cells that become increasingly diverse

6 weeks - Formation of hear and other internal organs, large neural tube

7 weeks - eyes, fingers, most internal organs have formed, not yet fully functional

7 weeks - facial features are visible (including mouth and tongue)
eyes have retina and lens
major muscle system is developed
the child has its own blood
these blood cells are produced

8-9 weeks - half an inch long. The baby is protected by the amniotic sac (filled with fluid) where child can swim. Arms and legs have lengthened and fingers can be seen. Brain waves can be measured.

9 weeks - an embryo turns into fetus

10 weeks - the heart is almost completely developed. Presence of bypass valve divert (child's body is oxygenated through the placenta. Twenty tiny teeths are forming in the gums.

12 weeks - webbing on the fingers Idigits still fused). Vocal chords are complete (a child can cry sometimes silently). The brain is fully formed.

14 weeks -muscles lengthen and become organized (mother can feel unborn child kicking and moving)

15 weeks - the fetus has an adult's taste buds. Foods the mother eats affects teh movement of the baby

4 months (16 weeks) - face is fully developed. HAir covers the skin. Eyes are formed but not yet functional

20 weeks - the child can hear and recognize mother's voice. The baby is growing and can possibly survive if born at this stage. FIngerprints appear. Sex organs are visible

5 months - REM sleep occurs. Sleep/wake cycles. Body position - head up. 50/50 chance of survival outside the womb.

24 weeks - child is covered with a fine hair called lanugo. Tinder skin are protected by a waxy substance called vemix.

30 weeks - nourishment is transferred from the mother;s food.

7 months - the baby is less able to move, room is tight. Most babies get into a head down position, getting ready for birth.

Critical period - a time during development when influences have major effect