Developmental:
Conception is the union of two gametes.
Prenatal Physical Development:
The germinal period: 0-2 weeks
At the beginning: Single cell zygote
End of the stage: Blastocyst
Main development: creation of inner mass inside the blastocyst, which forms an
embryo
The Embryonic period: 3-8 weeks
Beginning: about 2mm long
End of the stage: about 2.5cm long weighing about 4g
Main development: Heart begins to beat, development of neural tube. Neuron
production begins and neurons migrate to the body and brain. Development of for
arms, legs, fingers and toes. First movements
The foetal period: 9 weeks – birth
Beginning: 23mm long.
End of stage: average 50cm and weighing 3.2kg
Main development: body and nervous system begin to operate in an organised way.
Sex can be determined from week 14. By week 24 most brain neurons are formed.
Developmental processes:
Cell division
Cell migration: the movement of newly formed cells from their point of origin to
somewhere else in the embryo
Cell differentiation: specialisation of cells
Apoptosis: programmed cell death
Neuronal Proliferation:
Production of neurones begins in the embryo at week 3-4 and is active up to week
16. With hundreds oof neurons being made each minute and most being formed by
week 24. The head enlarges to one half of the body size by week 8.
Neuronal migration:
Between week 13 and 21 neurones move to different locations in the brain and
nervous system. Once they reach their destinations in the brain the neurones begin
to develop connections (synapses) Gilal cells begin to develop.
Neuronal differentiation:
Synaptogenesis: development of synapses amongst the emerging neurones
Myelination: coating of the axons in fatty insulating material to improve effienciy .
Pruning: developmental process through the synapses that are rarely activated are
eliminated. Synaptic pruning happens not only in the foetuses but in adolescence
and adult hood.
Conception is the union of two gametes.
Prenatal Physical Development:
The germinal period: 0-2 weeks
At the beginning: Single cell zygote
End of the stage: Blastocyst
Main development: creation of inner mass inside the blastocyst, which forms an
embryo
The Embryonic period: 3-8 weeks
Beginning: about 2mm long
End of the stage: about 2.5cm long weighing about 4g
Main development: Heart begins to beat, development of neural tube. Neuron
production begins and neurons migrate to the body and brain. Development of for
arms, legs, fingers and toes. First movements
The foetal period: 9 weeks – birth
Beginning: 23mm long.
End of stage: average 50cm and weighing 3.2kg
Main development: body and nervous system begin to operate in an organised way.
Sex can be determined from week 14. By week 24 most brain neurons are formed.
Developmental processes:
Cell division
Cell migration: the movement of newly formed cells from their point of origin to
somewhere else in the embryo
Cell differentiation: specialisation of cells
Apoptosis: programmed cell death
Neuronal Proliferation:
Production of neurones begins in the embryo at week 3-4 and is active up to week
16. With hundreds oof neurons being made each minute and most being formed by
week 24. The head enlarges to one half of the body size by week 8.
Neuronal migration:
Between week 13 and 21 neurones move to different locations in the brain and
nervous system. Once they reach their destinations in the brain the neurones begin
to develop connections (synapses) Gilal cells begin to develop.
Neuronal differentiation:
Synaptogenesis: development of synapses amongst the emerging neurones
Myelination: coating of the axons in fatty insulating material to improve effienciy .
Pruning: developmental process through the synapses that are rarely activated are
eliminated. Synaptic pruning happens not only in the foetuses but in adolescence
and adult hood.
