Placenta, umbilical cord and amnion
- Created by: hannahadams
- Created on: 25-05-15 21:43
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- Placenta, umbilical cord and amnion
- Placenta
- begins to develop at implantation and after approximately 12 weeks, it is a thick, disc-like structure with finger-like projections called villi that extend deep into the wall of the uterus.
- site of exchange by the process of diffusion
- provides important adaptions for diffusion:
- the rich blood system of the mother runs in a counter-current system to that of the foetus so there will always be a concentration gradient which allows diffusion into the foetal blood
- the blood systems of the mother and foetus are close together, separated by a thin membrane but not joined, reducing the length of the pathway for diffusion
- the villi provide a large surface area for exchange of dissolved nutrients, oxygen, carbon dioxide and urea
- amnion contains amniotic fluid
- umbilical cord:
- umbilical artery: carries urea, carbon dioxide and other wastes back to the mother
- umbilical vein: carries oxygen, glucose, amino acids and other nutrients from the mother to the foetus
- exchange of materials by diffusion only takes place in the placenta
- the role of the umbilical cord is the transport these materials to or from the foetus in the blood vessels of the umbilical artery and the umbilical vein
- the amnion contains amniotic fluid which cushions the foetus, supporting it during development and protecting it against mechanical shock and temperature fluctuations
- Placenta
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