Lecture 23 - Pulmonary Circulation and Gas Exchange

Question 1

What are the different zones of blood flow and where are they typically seen?

L23 S12

Answer 1

Zone 1:

• no blood flow
• mostly seen in pathological tissue

Zone 2:

• intermittent blood flow (during systole)
• seen in lung apices

Zone 3:

• continuous blood flow
• seen in lung bases; seen in apices during exercise

Question 2

What agents constrict or dilate pulmonary arterioles?

L23 S15

Answer 2

Constrict:

• norepinephrine
• epinephrine
• angiotensin II
• some prostaglandins

Dilate:

• isoproterenol
• acetylcholine

Question 3

What happens to blood flow in the lungs during exercise?

L23 S17

Answer 3

• increases number of open capillaries
• distends capillaries and increases blood flow
• slight, but minimal, increase in pulmonary arterial pressure

Question 4

How much new air is brought into the alveoli with each breath?

L23 S31

Answer 4

-350ml (~1/7 the total capacity)

Question 5

How high can alveolar ventilation increase pO2 to?

L23 S34

Answer 5

-149mmHg (maximum pO2 in humidified air at sea level

Question 6

What factors effect how fast a gas will diffuse across a membrane?

L23 S44

Answer 6

• membrane thickness
• membrane surface area
• diffusion coefficient of gas across the membrane
• difference of partial pressure of the gas across the membrane

Question 7

What is the ventilation-perfusion ratio?

L23 S46

Answer 7

Va/Q

Va= alveolar ventilation (4L/min)

Q= pulmonary blood flow (5L/min)