Placental function Flashcards
How does placental efficiency increase to support fetal growth?
- Increased blood flow via umbilical and uterine BV
- Incresased cotyledonary microvascular density
Describe factors that influence the passive exchange of nutrients via the placenta
- Blood flow (efficiency must increase)
- Large SA for exchange
- Electrical gradient= slightly negative which encourages + ions
- Concentration gradient
- Number of tissue layers involved
Name a species that has a highly efficient counter current placental blood flow system
Rabbit
In late gestation, what does the fetus do to improve maternal glucose transfer?
-Increases O2 consumption which increases the concentration gradient
What nutrients does the placenta use active transport to move? What affects the active transport?
- Amino acids and glucose
- It is determine by passive mechanisms and density/ activity of carrier molecules for Aa and glucose.
Amino acids are high in fetal blood than mothers. How is this achieved?
-By Aa transporters that are located on the placental tissue (the conc of these transports can increase during gestation to cope with increased demand in late pregnancy)
What does IUGR stand for?
- Intra-uterine growth retardation
- The failure for the fetus or its organs to grow to full potential
- It is associated with insufficient Aa
What is the primary glucose transporter in the placenta?
GLUT -1
What are the different causes of IUGR?
- Maternal/ fetal metabolic & homeostatic mechanisms
- Temperature/ stress
- Insufficiency of uterus endometrium
- Insufficient placenta
- Maternal intestinal malabsorption
- Ingestion of toxic substances
- Maternal nutritional imbalance
What is ‘nutrition induced placental growth restriction in adolescent sheep’?
-When a ewe lamb (a lamb old enough to establish a pregnancy BUT is not finished growing herself) becomes pregnant and is fed a high nutrient diet, the placenta size is smaller than ewe lambs fed on a moderate nutrient diet.
Idea is that because the ewe lamb is still growing herself the mother’s body takes more of the nutrients instead of giving it to the fetus.
-NURTIENT PARTITIONING OCCURS IN FAVOUR OF THE MOTHER
What is the human maternal-fetal interface?
- Human placenta are invasive and haemachorial. Some of the fetal cells invade into the uterine tissue. They also invade up some of the spiral arterioles and imbed themselves into the endothelium of the BV. Once they’ve done this, some of the fetal cells prevent the BV responding to vasoconstriction by converting it to a distended tube.
- THIS MEANS THE FETUS CIRCULATION IS NOT IMPACTED BY MOTHER’S STRESS
Explain what happens during pre-eclampsia
- You get reduced invasion of the trophoblast cells into the arteries. These converted spiral artery are required to support pregnancy, when there aren’t enough of them the mother has to work very hard to deliver enough blood to the fetus
- THIS RESULTS IN HIGH BP AND TOXAEMIA
