Lecture 1 - Pre-natal Development Flashcards
Preformationism
Prior knowledge of prenatal period suggesting that mini people lived in sperm and started to grow when the sperm met the egg.
Epigenesis
What we know now - that new organs and structures develop through a series of stages
Pre-natal development stages
1- Germinal period
2- Embryonic period
3- Foetal period
1-Germinal Stage
Conception begins when a sperm penetrates the membrane of an ovum
2-Embryonic period (2-8 weeks)
Zygote attaches to uterine wall and becomes an embryo
Amniotic sac
Provides an even temperature and cushioning
Placenta
Permits the exchange of materials from the mother
Inner cell divides into 3 layers to help form key structures
1-Ectoderm
2-Mesoderm
3-Endoderm
Ectoderm
Becomes the nervous system, nails, teeth, inner ear, lens of the eyes and skin
Mesoderm
Becomes muscles, bones, circulatory system, inner layers of skin and internal organs
Endoderm
Becomes the digestive system, lungs, urinary tract and glands
3-Foetal period (9 weeks-birth)
Growth and development, development of sexual organs, distinct patterns of rest, respond to sensory stimuli
Touch
- First system to function
- Foetuses curl fingers and toes when touched
- Initially move away from the source of facial touch but later they move towards it
- Touch their own face more than any other part of their body
Chemosensory system (taste and smell)
- Substances in amniotic fluid can stimulate the foetus’ chemoreceptors
- Molecules from mothers diet, perfume on skin and concentrations of airborne substances can pass into amniotic fluid via bloodstream
- Show a preference for sweet substances over bitter
Visual System
- Very little visual stimulus
- Eyelids are fused shut shortly after development and don’t open until 5-7 months of gestation
- Eyes sometimes make slow, rolling movements or fast jerky movements
