Exam 6: Fetal and Avian Gas Exchange Flashcards
Where does gas exchange occur in the fetus?
Placenta
When is surfactant produced?
At about 85% of term
What is the surge in surfactant production just before birth a result of?
Maternal and fetal corticosteroid production
Why is surfactant important?
Reduces surface tension at the air/liquid interface in the lung
It maintains alveolar diameter, so it does not collapse on itself
Surfactant gets spread around within the alveoli during the first breath
Is systemic blood pressure lower or higher in the fetus than in the dam?
Lower
What is the PO2 of blood reaching the fetal brain?
17 mmHg
What changes occur during birth that alter the function of the respiratory system during passage through the pelvis?
Decrease/expels fluid from lungs
What changes occur during birth that alter the function of the respiratory system during the first breath?
Eased PVR (decreased HPV) Increased SVR (vasoconstriction and termination of placental circulation)
What changes occur during birth that alter the function of the respiratory system during termination of placental circulation?
Arterial constriction (stretching and increased PO2) Umbilical veins do not constrict (autotransfusion)
What changes occur during birth that alter the function of the respiratory system during closure of ductus arteriosus?
Active vasoconstriction
Increased PO2
Decreased prostaglandins help to close ductus arteriosus
What is unique about fetal hemoglobin?
It has a higher affinity for oxygen so that uptake is easy from the maternal hemoglobin to the fetal hemoglonim
What makes the avian respiratory system unique?
No diaphragm
Air sacs are connected to each other, the lung, and the pneumatic bone
Higher surface area/volume ratio
Thinner blood-air barrier
Gas exchange occurs in tertiary parabronchi
Birds have a lower function residual capacity
Avian hemoglobin is left shifted
