Biology Module 3 - 3.sexual reproduction in humans 3.10 explain the structure and functions of the placenta

3.10 explain the structure and functions of the placenta



Structure of the placent


Diagram of structure of placenta

source

chorionic villi - many finger like projections into the uterus wall which contain the fetal capillaries

Chorion - develops from fetus

Function of placenta


gas exchange

• oxygen from the mother's haemoglobin diffuses across the thin barriers separating it from the foetus' blood and combines with foetus' haemoglobin. oxygenated blood flow to the foetus in the umbilical view 

NB large surface area provided by the villi enables gas exchange by mother and foetus to take place rapidly

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exchange of substance between maternal blood and foetus' blood                                

•  glucose is transported by facilitated diffusion

• urea diffuses from foetus to mother is readily transported across placental barrier into mother's blood to be removed by kidney's

• antibodies, inorganic ions and water move across placenta to feotus

• amino acids are transported by active transport

• protection - prevents and reduces movement of larger molecules and pathogens into foetus 

• foetus isolated from pressure changes in mother blood  

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secretion of hormone 

• progesterone and oestrogen causes enlargement of breasts and maintain the endometrium. progesterone also inhibits contraction of muscles in mymetrium                  

• removal of placenta causes a decrease of hormones so cause                                      lactation