Human Development Chart

Human Development Chart
sperm & ovum form		Zygote - single cell capable of growth into a human being
zygote		lasts 30 hours, then makes first division
morulla or blastula	up 5days	ball of undifferentiated totipotent cells
Blastocyst	by day 5	Hollow Ball of cells, external and internal different. ca. 100 cells inner 50 are pleuripotent stem cells. External will become placenta, internal will become embryo
	day 7 - 9	Blastocyst implants in wall of uterus (55% of Zygotes never reach this stage.)
	day 14 - 16	Blastocyst develops line of dark cells down centre that will become the spinal chord. Real differentiation has begun.
Embryo	day 14 to week 8
Embryonic phase: gastrula	day 30	Lengthens and differentiates into ecto-, meso-, & endo derm
Embryonic phase ends	week 8	At this point enough development to call a foetus. All organs and structures found in a newborn infant are now present.
foetus	week 9- 12	Major organs have begun to develop. Recognisably human, but cannot survive outside the womb.
		15 % of pregnancies miscarry during weeks 4-12
foetus	week 13 - 16	About 6 inches long
foetus	week 20	Reaches about 8 inches long.
foetus	week 24	About 11 inches long and weighs about 1lb 10 oz.
foetus	weeks 29 - 39	Most healthy foetuses delivered during this period survive, earlier ones may need mechanical help to survive.
birth of baby	week 39
infant	0-5 yrs	Baby Toddler Infant dependent human life
child	8 - 11 yrs	Capable of independent survival
adult human life	18+ yrs