Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
43 Cards in this Set
- Front
- Back
|
T/F: highly oxygenated blood from the placenta bypasses the hepatic portal system, sending highly oxygenated blood up the IVC.
|
False. Incoming blood is shunted into the IVC, however highly oxygenated blood is first mixed with poorly oxygenated fetal blood
|
|
|
What type of diffusion is demonstrated when oxygen in the maternal circluation crosses the placental membrane?
|
Simple diffusion
|
|
|
T/F: in the fetus, O2 travels up its PO2 gradient from the tissues to RBC.
|
False, oxygen travels down its PO2 gradient from RBCs to the tissues
|
|
|
Give Fick's law and define the terms in biological terms.
|
Rate of diffusion = (K x A x [P2-P1])÷d…. K=experimentally determined rate constant at a given temperature… A= surface area… P2-P1=the difference in partial pressures across the membrane… d= the distance (thickness) over which diffusion takes place across the membrane
|
|
|
Which placental pathology can diminish the A (area of the placental membrane), and what effect does this have on diffusion? what can this result in?
|
1) placental abruption -->Infarction, … 2) decreased rate of diffusion... (3) results in intrauterine growth retardation
|
|
|
What is placental abruption?
|
the placental lining being separated from the uterus of the mother
|
|
|
What part of the flux equation would be effected by the development of villus edema? 2) what effect does this have on the diffusion rate of O2? Give an example.
|
"d" (the distance a molecule of O2 travel to move from maternal RBCs to fetal RBCs) is in general increased by conditions which villus edema develop… 2) increase in "d" decrease the rate of O2 diffusion... 2) syphilis
|
|
|
What is the most influencial factor in determining the rate of O2 diffusion from maternal RBCs to fetal RBCs?
|
P2-P1: concentration gradient of O2 from maternal plasma to fetal plasma
|
|
|
What 2 things are needed to maintain a O2 concentration gradient from maternal plasma to fetal plasma? What 2 things causes most of the problems in maintaining an adequate O2 concentration gradient?
|
Persistent diffusion is dependent on adequate blood flows in both the maternal and fetal circulation near the placenta… 2) Most problems arise from decreased umbilical/ or uterine blood flow
|
|
|
What is fetal PO2? Is this high or low? What three things cause such a low fetal PO2?
|
Fetal PO2=35 torr… 2) Low compared to maternal PO2… 3) a) high rate of placdental consumption, b) fetal blood is mix (umbilical + less oxygenated blood within fetal circulation), c) the placenta is an imperfective equilabrator of maternal and fetal circulation
|
|
|
Name 3 sets of major fetal arteries in the order of decreasing PO2.
|
Highest PO2:Aorta (above the ductus arteriosus from ejected LV) > arteries below the ductus arteriosus (mixture of RV & LV) > pulmonary arteries (from RV only): lowest PO2
|
|
|
Which has the lowest PO2, LV or RV ejected blood?
|
RV
|
|
|
What 3 things have an innate adverse effect on fetal oxygenation?
|
Fetal circulation arrangement, high placenta O2 consumption, inefficient placental O2 equilabration
|
|
|
What are the 2 main maternal adaptations that increase blood flow to the fetus during pregnancy?
|
a) high uterine venous PO2, and b) at term fetal O2 accounts for 15% of mom's cardiac output
|
|
|
The fetus has a low PO2 torr, yet O2 delivery to tissues is good. What 3 things account for this?
|
biochemical, anatomical, physiology
|
|
|
What's the advantage of fetal cells have a greater O2 affinity than mom's?
|
under normal physiologic condition the circulating fetal cell returns well saturated with O2… as a consequence, O2 content and saturation in fetal blood (with a low PO2)is higher than it would be if adult hemoglobin were present
|
|
|
is the difference in O2 content between maternal and fetal proportionally greater or lesser than the PO2 difference?
|
the O2 content difference between fetus and mom is much less than the difference in PO2
|
|
|
Which is more saturated at low pO2 maternal or fetal hemoblobin?
|
fetal
|
|
|
Name the 3 anatomical fetal shunts
|
ductus venosus, foramen ovale, ductus arteriosus
|
|
|
What does the ductus venosus do?
|
shunts 50% of umbilical venous blood from the HPS --> IVC
|
|
|
What does the foramen ovale do?
|
shunts blood from the RA to the LA
|
|
|
What does the ductus arteriosus do?
|
shunts blood from the Pulmonary artery to the aortic arch
|
|
|
Describe the fetal circulation from the umbilical venous blood to the brain/myocardium.
|
Umbilical venous blood ->ductus venousus -> IVC -> right heart -> (1) foramen ovale -> LV -> CIRCULATION (2) Pulmonary artery -> ductus arteriousus -> aortic arch -> CIRCULATION
|
|
|
What 3 fetal hemodynamics optimize O2 delivery to tissues?
|
increased CO, increased systemic blood flow rate, CO is adjustable to meet O2 deprivation
|
|
|
In deprivation, which 4 organs receive more blood flow and which receive less? (hint: fab 4)
|
More: heart, brain, placenta, adrenal glands… Less: kidney, gut, skeletal muscles
|
|
|
What does decreasing blood flow to certain organs provide resistance to?
|
hypoxia
|
|
|
What does prolonged O2 deprivation lead to?
|
↓ CO, ↓ BF, hypoxia, acidosis, death
|
|
|
What does decreased blood flow in a fetus cause, alkalosis or acidosis?
|
acidosis
|
|
|
At birth adaptation to breathing must occur immediately… what 2 things initiates breathing?
|
Hypoxia, sudden skin cool
|
|
|
What is need for the first breath to be taken, ↓ or ↑ in intrathoracic pressure?
|
↑↑↑ in intrathoracic pressure
|
|
|
What are the effects of the cessation of blood flow to: a) systemic vascular resistance, b) left heart pressure
|
↑ in both systemic vascular resistance AND left heart pressure
|
|
|
What are the effects of lung expansion AND increased pO2 in a newborn?
|
↓ in pulmonary pressure -> ↓ right heart pressure
|
|
|
What is the effect of increased LA pressure and decreaed RA pressure on the newborn?
|
closure of the formen ovale
|
|
|
What causes the closure of the Ductus Arteriosus? How long does this take? What can cause a patent ductus arteriosis?
|
Oxygenated blood flowing through the DA causes its constriction… b) closes in 1-8 days… c) hypoxia -> ↓ in bradykinins (in utero or at birth) -> cause a PDA
|
|
|
How long does it take for the ductus venosus to close? What causes its closure?
|
1-3 hrs… cause unknown
|
|
|
What effect does syphilis have on blood flow in the placenta?
|
placental swelling --> ↑ d= reduced diffusion rate
|
|
|
What is the advantage of a low pO2 in the fetus side of the placenta with a high pO2 on the maternal side?
|
facilitates simple diffusion
|
|
|
What effect does maternal asthma have on fetal oxygenation?
|
What effect does maternal asthma have on fetal oxygenation? p2-p1 = decreasese placental O2
|
|
|
Between biochemical, anatomical and physiological factors, which is least important in fetal oxygenation?
|
biochemical
|
|
|
What causes the Bohr effect in fetal oxygenation?
|
accumulation of CO2 + H+ on the fetal side --> follow the concentration gradient to the maternal side --> RESULTS: ↑ pH on fetal side… ↓ pH on maternal side of placenta
|
|
|
What effect does a high or low pH have on O2 affinity of blood to oxygen?
|
↓ pH = ↓ O2 affinity… ↑ pH = ↑ affinity (fetal)
|
|
|
Where is the sphincter located that allocates more blood for fetally important organs?
|
spincter located at the mouth of the ductus venosus
|
|
|
What effect does ↓ pO2 have on: HR, CO, mean arterial pressure, stroke volume, tissue O2 allocation?
|
↑ CO, ↓ HR, ↑ mean arterial pressure, ↑ SV, allocation to fetally relevant tissues
|
