Lesson 11: Gas Exchange and Midterm 1 Review

Question 1

what is ventilation - perfusion?

Answer 1

the matching of the airflow to the alveoli and the blood flow to the pulmonary capillaries

Question 2

why does the capillaries at the bottom of the lungs have high levels of blood flow?

Answer 2

because gravity pulls blood down

Question 3

in order to counteract mismatching blood flow, it is regulated by?

Answer 3

reflex hypoxic vasoconstriction of the pulmonary arterioles

Question 4

the reflex hypoxic vasoconstriction system can sense when an area is in a shunt. so what does it do?

Answer 4

it constricts the blood vessels to decrease the blood flow to the areas of low VQ and it redistributes it throughout the lung
- helps to maintain highly efficient and effective gas exchange

Question 5

there needs to be a certain amount of ____ in the capillaries for equilibrium in PO2.

Answer 5

time
- about 0.25-0.5 seconds while its only in it for 0.75 at rest

Question 6

higher cardiac output can lead to what in the slow of pulmonary capillaries?

Answer 6

higher cardiac output –> faster flow in pulmonary capillaries –> less time for diffusion
- during exercise, the end-capillary goes further left (leaves the capillary faster, before equilibrium)

Question 7

inadequate gas exchange can occur when:

Answer 7

• the surface area for gas-exchange is decreased (emphysema; destroyed capillary networks. alveolus have less capillaries around them and they actually expand - merge into one alveolus)
• thickness of the barrier separating the air and blood is pathologically increased

Question 8

true or false: increased interstitial thickening can impair the ability of diffusion

Answer 8

true (area between the capillary and alveolus is farther apart)

Question 10

What can a shunt do to the arterial PO2?

Answer 10

Lower it. This is because the blood is now receiving less oxygen