How does the body create it? How is it structured? How does it keep the baby alive? How does it attach/detach from the uterus?
In: 2
Formation
Formed partly from stem cells from the same group that goes onto form the fetus, and partly from the endometrium, the lining of mum’s uterus. They grow blood vessels that line up very close together (but don’t mix so there is t a mixing of mum and baby’s blood).
Coming out roughly the centre of the placenta on the baby’s side is the umbilical cord which attaches to the fetus at the belly button (the belly button is kind of like a scar from where the umbilical cord came off). Within the cord are an umbilical vein and two umbilical arteries (sometimes only one). These allow blood to go to and from the placenta from the fetus.
Function
Providing oxygen; foetuses have a slightly different haemoglobin (Hb is the red protein that holds onto oxygen and transports it to where it’s needed). Because it is slightly different it holds onto oxygen slightly better so that when the blood in the baby’s part of the placenta comes close to the mum’s blood in her part oxygen is able to move from mum’s blood to baby’s and be picked up
Nutrients: the fetus gets all its nutrients and fluid from the mother. Some of these diffuse into the fetus’s blood from the mothers just down a concentration gradient. Other components are actively transported by proteins in the cell membranes.
Waste excretion
The fetus creates waste products, like carbons dioxide, that needs to be gotten rid of. This goes from fetus’ blood to maternal blood down the concentration gradient
Hormone production
There are a number of hormones that the placenta produces that keep the pregnancy going and also alter mum’s metabolism to free up energy for the fetus.
Protection to fetus and mother
Because the bloods of mother and fetus don’t mix, the baby is protected from mum’s immune system. If it did mix then the immune system would recognise the fetus as a foreign object and try to fight it in the same way as an infection or a transplanted organ.
The placenta also protects the fetus from infections (mum can have an infection and the fetus not be infected).
Bye bye placenta
After the baby is born, the uterus continues to contract which physically compresses the placenta. There is also loss of blood going back to the placenta from the baby as the vessels in the cord contract when the cord gets cold, and then when the cord is cut. You also get the blood vessels within the placenta and uterus contracting. There are other hormone mechanisms as well. All of these together allow the placenta to separate from the uterus without too much blood loss from mum or baby.
Extra info
The longer it takes to separate from the uterus the higher the chance of there being a large bleed from mum. One of the fastest ways to bleed to death is from a postpartum bleed. Most bleeds are small but it can be catastrophic. For this reason, in most or all developed countries, most placental deliveries are “actively managed” rather than letting it occur completely naturally. The mother is given an injection into her thigh after the baby is delivered. It is a synthetic version of oxytocin, which is a hormone that mum’s brain produces to cause the separation. This injection speeds up the separation and reduces the risk of severe PPH. The risk of severe PPH is higher in women who have had lots of previous pregnancies and they will often be given a double dose of syntocin, one into the muscle and one into a vein at the same time to offset this increased risk
I have now completed your crash course in the placenta. Feel free to forget it all
How does the body create it? How is it structured? How does it keep the baby alive? How does it attach/detach from the uterus?
In: 2
Formation
Formed partly from stem cells from the same group that goes onto form the fetus, and partly from the endometrium, the lining of mum’s uterus. They grow blood vessels that line up very close together (but don’t mix so there is t a mixing of mum and baby’s blood).
Coming out roughly the centre of the placenta on the baby’s side is the umbilical cord which attaches to the fetus at the belly button (the belly button is kind of like a scar from where the umbilical cord came off). Within the cord are an umbilical vein and two umbilical arteries (sometimes only one). These allow blood to go to and from the placenta from the fetus.
Function
Providing oxygen; foetuses have a slightly different haemoglobin (Hb is the red protein that holds onto oxygen and transports it to where it’s needed). Because it is slightly different it holds onto oxygen slightly better so that when the blood in the baby’s part of the placenta comes close to the mum’s blood in her part oxygen is able to move from mum’s blood to baby’s and be picked up
Nutrients: the fetus gets all its nutrients and fluid from the mother. Some of these diffuse into the fetus’s blood from the mothers just down a concentration gradient. Other components are actively transported by proteins in the cell membranes.
Waste excretion
The fetus creates waste products, like carbons dioxide, that needs to be gotten rid of. This goes from fetus’ blood to maternal blood down the concentration gradient
Hormone production
There are a number of hormones that the placenta produces that keep the pregnancy going and also alter mum’s metabolism to free up energy for the fetus.
Protection to fetus and mother
Because the bloods of mother and fetus don’t mix, the baby is protected from mum’s immune system. If it did mix then the immune system would recognise the fetus as a foreign object and try to fight it in the same way as an infection or a transplanted organ.
The placenta also protects the fetus from infections (mum can have an infection and the fetus not be infected).
Bye bye placenta
After the baby is born, the uterus continues to contract which physically compresses the placenta. There is also loss of blood going back to the placenta from the baby as the vessels in the cord contract when the cord gets cold, and then when the cord is cut. You also get the blood vessels within the placenta and uterus contracting. There are other hormone mechanisms as well. All of these together allow the placenta to separate from the uterus without too much blood loss from mum or baby.
Extra info
The longer it takes to separate from the uterus the higher the chance of there being a large bleed from mum. One of the fastest ways to bleed to death is from a postpartum bleed. Most bleeds are small but it can be catastrophic. For this reason, in most or all developed countries, most placental deliveries are “actively managed” rather than letting it occur completely naturally. The mother is given an injection into her thigh after the baby is delivered. It is a synthetic version of oxytocin, which is a hormone that mum’s brain produces to cause the separation. This injection speeds up the separation and reduces the risk of severe PPH. The risk of severe PPH is higher in women who have had lots of previous pregnancies and they will often be given a double dose of syntocin, one into the muscle and one into a vein at the same time to offset this increased risk
I have now completed your crash course in the placenta. Feel free to forget it all
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