The three periods of prenatal development:
1. Germinal: From fertilisation to implantation (10 days).
● Blastocyst forms (50-60 cells).
2. Embryogenesis: From implantation to 8 weeks.
● Gastrulation (3-4 weeks): Distinct layers in embryo.
○ Mesoderm: Muscle, bone, circulatory and reproductive systems.
○ Endoderm: Digestive and respiratory systems.
○ Ectoderm: Skin and neural system.
● Neural tube begins to close (4 weeks): Precursor to spinal cord and brain.
● Sex differentiation (7-8 weeks).
3. Foetal: From 8 weeks to birth
● Basic structures of brain & CNS in place (9 weeks).
○ Foetus responds to touch, then taste.
○ 23-27 weeks: Begin to hear sounds (startle reflex).
○ 32 weeks: Can track bright lights displayed outside the womb.
● 24 weeks: First facial movement.
● 19-35 weeks: Anticipation of movement.
At birth, the brain weighs about 25% of an adult brain and is about 30% the size of an adult
brain.
Epigenetics: The study of heritable phenotype (environmental) changes that do not involve
alterations in the DNA sequence.
Influences on prenatal development:
1. Maternal nutrition can impact physical and cognitive growth.
2. Maternal environment (diet, habits, exercise, stress).
3. Maternal stress can turn gene expression in foetus on or off.
○ Especially linked to foetal responses to stress (modified by experiences
during development)
1. Germinal: From fertilisation to implantation (10 days).
● Blastocyst forms (50-60 cells).
2. Embryogenesis: From implantation to 8 weeks.
● Gastrulation (3-4 weeks): Distinct layers in embryo.
○ Mesoderm: Muscle, bone, circulatory and reproductive systems.
○ Endoderm: Digestive and respiratory systems.
○ Ectoderm: Skin and neural system.
● Neural tube begins to close (4 weeks): Precursor to spinal cord and brain.
● Sex differentiation (7-8 weeks).
3. Foetal: From 8 weeks to birth
● Basic structures of brain & CNS in place (9 weeks).
○ Foetus responds to touch, then taste.
○ 23-27 weeks: Begin to hear sounds (startle reflex).
○ 32 weeks: Can track bright lights displayed outside the womb.
● 24 weeks: First facial movement.
● 19-35 weeks: Anticipation of movement.
At birth, the brain weighs about 25% of an adult brain and is about 30% the size of an adult
brain.
Epigenetics: The study of heritable phenotype (environmental) changes that do not involve
alterations in the DNA sequence.
Influences on prenatal development:
1. Maternal nutrition can impact physical and cognitive growth.
2. Maternal environment (diet, habits, exercise, stress).
3. Maternal stress can turn gene expression in foetus on or off.
○ Especially linked to foetal responses to stress (modified by experiences
during development)
