Download - Fetal development
FETAL DEVELOPMENT
THE FIRST ELEVEN DAYS OF HUMAN DEVELOPMENT
Ovum and Sperm
First Cell Divison
Blastocyst showing inner cell mass
Trophectoderm (will become placenta)
Inner cell mass (will become baby)
Trophectoderm
Inner cell mass
Zona pellucida
Blastocyst
Cell Differentiation
By the end of the first week, cell differentiation occurs to create two tissue types:
Ectoderm – forms outer skin, sensory organs, entire brain and nervous systemEndoderm – forms the internal organs (gut, lungs, liver, glands
By the end of the second week, the third cell type differentiation occurs
Mesoderm – forms the bones, muscles, connective tissues, circulatory system, and smooth muscles of the digestive system
Spinal Cord and Nervous System Formation
Neurogenesis starts in the third week after fertilization, creating neurons at a rate of over 250,000 per minute
The synapses for each neuron are created – up to 15,000 synapses per neuron – at a rate of 1.8 million synapses per second between 8 weeks gestation and 2 years after birth
By 9 weeks the spinal cord is formed and starting to function
Brain
Eye
Heart
Liver
Arm bud
Leg bud
Umbilicalcord
Placenta
Yolk sac
Embryo at 5 weeks from conception
6 week old embryo in sac
Embryo at 6 weeks after conception
Heart
Eye
Arm bud
Leg bud
Umbilical cord
Embryo in sac at 8 weeks after conception
Hemispheres of brain
Placenta
Close-up of hands at 10 weeks LMP
Fetus at 12 weeks
Hand at 12 weeks
Fetus at 3+ months
Ear at 3+ months
Fetus at 15 weeks
Fetus at 15 weeks
Foot at 16 weeks
Sucking thumb at 18 weeks
Female fetus at 18 weeks
Ear at 5 months
Fetus at 5 months
Fetus at 24 weeks
Fetus at 7 months
Fetus at 36 weeks
Full term baby at 39 weeks, after “finishing touches”