The Placenta Flashcards
What is the placenta?
- a disc-shaped temporary organ
- richly supplied with maternal and foetal blood vessels
What does the placenta connect?
- the foetus with its mother’s blood
- at the end of the umbilical cord
What does the placenta develop from?
- the chorion and its villi (that penetrate the endometrium)
What is the importance of the villi on the chorion that the placenta develops from?
- the villi provide a large surface area of attachment of the placenta to the endometrium
What does each placental villus contain and why?
- each villus contains a capillary network
- which provides a large surface area for exchange of substances by diffusion
What are the placental villi surrounded by and why?
- the mother’s blood
- so that mother’s blood supply and foetal capillaries are very close to each other
Does the foetal and mother’s blood mix? Why or why not?
- no
- because the foetal capillaries have thin walls
How do substances move between the maternal and foetal blood?
- by diffusion
What would happen if the mother’s blood mixed with the foetal blood?
- it could cause the foetal blood to clot
- resulting in the death of the foetus
What is the 1st function of the placenta?
- Oxygen and dissolved food substances pass from the mother to the foetal blood system for respiration and nutrition
What are some examples of dissolved food substances that pass from the mother to the foetal blood system through the placenta?
- glucose
- amino acids
- fatty acids
- ions
- vitamins
What is the 2nd function of the placenta?
- Foetal waste products of metabolism pass into the maternal blood system for excretion
What are some examples of foetal waste products of metabolism that pass into the maternal blood system for excretion?
- urea
- carbon dioxide
What is the 3rd function of the placenta?
- Some maternal antibodies pass to the foetus, providing temporary passive immunity to certain diseases
What is the result of antibodies being passed to the foetus through the placenta?
- the child enjoys immunity to most infectious diseases for the first 6 months of life
What is the 4th function of the placenta?
- The placenta acts as a barrier (micro filter)
- preventing many pathogenic organisms and drugs from entering the foetus from the mother
What are some examples of pathogens that can pass through the placenta to the foetus?
- German measles (rubella)
- syphilis
- HIV
What does the placenta do after 3 months of pregnancy? (5th placental function)
- The placenta takes over the function of secreting progesterone and oestrogen from the ovaries (corpus luteum)
Why are progesterone and oestrogen important in pregnancy?
- these hormones are essential from brining about the necessary changes in the uterus
- and for the maintenance of pregnancy
What does progesterone do in pregnancy?
- prevents ovulation and menstruation
- which would result in the loss of the foetus
What does the placenta secrete late in pregnancy and why?
- relaxin
- a hormone that relaxes joints and ligaments to assist in the delivery of the baby
What kind of harmful substances can pass though the placenta and cause significant damage to the developing embryo and foetus?
- cigarette smoke (carbon monoxide and nicotine)
- alcohol
- illegal drugs
- many medicines