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PHYSIOLOGY OF PREGNANCY, PARTURITION, & LACTATION
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PHYSIOLOGY OF PREGNANCY, PARTURITION, & LACTATION
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PHYSIOLOGY OF PREGNANCY, PARTURITION, &LACTATION
The mature placenta is composed of what 3 major structures?
Chorionic villi, intervillous space, decidua basalis
What is the Functional unit of the placenta?
Chorionic villi
Spiral arteries from the mother empty directly into what?
Intervillous space and drained by maternal veins.
Describe the pathway of maternal blood flow
Blood enters in pulsatile spurts through the wall of the uterus and moves into the
intervillous space toward the chronic plate. Maternal blood is trapped in the intervillous
space. After the blood bathes the chorionic villi, it drains through venous orifices in the
basal plate, enters larger maternal placental veins, flows into the uterine and pelvic
veins.
There are No CAPILLARIES between maternal arterioles and venues. What acts as a
functional capillary in the maternal blood flow pathway?
INTERVILLOUS SPACE acts as a fuctional capillary
,List factors regulating MATERNAL blood flow?
Maternal blood pressure, intrauterine pressure, and pattern of uterine contraction
(attenuate arterial inflow and completely interrupt venous drainage).
What is the origin of Fetal blood flow?
Originates from 2 umbilical arteries, which carry deoxygenated blood, unlike systemic
arteries after birth.
Blood that has obtained a significantly high O2 and nutrient content returns to the fetus
from the placenta through the ____________.
umbilical vein
List two important functions of amniotic fluid?
Serves as a mechanical buffer protecting the fetus from external, physical insults
Fetus excretes waste products through it.
What is the gas composition of Maternal blood coming into the intervillous space?
Similar to systemic arterial blood:
PO2=100mmHg
PCO2=40mmHG
pH=7.4
, Diffusion of O2 from the maternal blood into the chorionic villi of the fetus causes the
PO2 of blood in the intervillous space to _____.
FALL.
PO2= 30-35mmHg
P02 of blood in the umbilical vein is even less
Describe how the fetus gets adequate oxygenation despite relatively low PO2 of the
maternal blood in the intervillous space?
Fetal Hb has a much higher affinity for O2 than maternal Hb. SO the fetal Hb can
extract O2 from maternal Hb.
Other mechanisms: Relatively high cardiac output per unit body weight of the fetus and
increase O2-carrying capacity of fetal blood in late pregnancy = Hb concentration rises
to a level of 50% higher than an adult.
For the following describe the mechanism for movement across the placenta (fetus to
mother):
Waste products urea & creatinine
Lipid-soluble steroid hormones
Glucose
Amino acids
Vitamins & minerals
LDL, transferrin, hormones, & antibodies (e.g., immunoglobulin G)
Waste products urea & creatinine = passive movement
Lipid-soluble steroid hormones = simple diffusion
Glucose = facilitated diffusion (Glut 1)
Amino acids = secondary active transport
Vitamins & minerals = active transport
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