4: Placenta, metabolism, birth weight Flashcards
At what point of the pregnancy is the “placental growth spurt”? “Fetal growth spurt”?
Placentas growth spurt is in the first half of pregnancy, fetus is in the last trimester.
Which comes first- embryonic or placental growth?
Embryonic then placental growth.
What are some of the main functions of the placenta?
Exchange of nutrients, respiratory gases, and metabolic waste. Protects growth and is a source of hormones.
Is there mixing of the fetal and maternal blood?
No direct mixing.
What does the amniotic sac enclose?
The embryo, amniotic fluid, and forms the epithelial covering of the umbilical cord.
What is the source of most of the amniotic fluid?
Maternal blood (diffusion)
What is the function of the amniotic fluid?
Shock absorption, prevents desiccation (dryness), allows room for fetal movements, assists in regulation of fetal temperature.
What is the fetal surface of the placenta called?
Chorionic plate.
What cells connect the placenta to the uterus and provide an area where materials can be exchanged?
Cytotrophoblasts. Act tumour-like to invade mothers uterus and establish blood flow to fetus.
What is the space called that the maternal blood enters (major functional unit of the placenta)?
Chorionic villus
When does the fetus begin to excrete urine into the amniotic cavity?
First trimester.
What are some examples of products that are synthesized by the placenta for the fetus?
Glycogen, lactate, cholesterol.
Does the fetal affinity for oxygen differ from the mothers?
Yes, the fetus has a greater affinity for oxygen due to the greater binding capacity of fetal hemoglobin.
Is there a difference in glucose levels between maternal and fetal blood during hyperglycemia? Why?
Glucose levels are lower for the fetus than the mother. Protects fetus from glycstion, which can be teratogenic.
What substances are transported to the fetus by passive diffusion?
Oxygen, carbon dioxide, fatty acids, steroids, electrolytes, fat soluble vitamins (generally poor transfer tho)
What substances are transported to the fetus by active transport?
Amino acids, cations, water soluble vitamins
What substances are transferred to the fetus by facilitated diffusion?
Sugars, long chain PUFA
How does the size of the placenta relate to the size of the fetus?
The fetus size is directly proportional to the placental size.
Does blood flow through the placenta stay constant through the duration of the pregnancy?
No, to compensate for the increased fetal needs later in the pregnancy, placental blood flow increases in the last trimester. Also compensates for the lower rate of placental growth compared to the fetal growth.
What partially accounts for the deceleration of fetal growth rate in the last 4 weeks of gestation?
Decline in the quantity of nutrients transferred per g fetal mass per unit time. Fetus increasing size so much, limited by size of placenta and amount of blood that can flow through the placenta.
What are lower concentrations of essential fatty acids in maternal and fetal blood associated with?
Lower birth weight, short gestation (preterm), and small head circumference.