Lecture 23: Pulmonary Circulation and Gas Exchange

Question 1

What is the circulation of high pressure; low flow in the lungs?

Answer 1

thoracic aorta- bronchial arteries- trachea, bronchial tree, adventitia, CT

Question 2

What is the circulation of low pressure, high flow?

Answer 2

pulmonary artery and branches- alveoli

Question 3

What is pulmonary arterial pressure?

Answer 3

24/9 mm Hg

Question 4

What is mean pulmonary arterial pressure?

Answer 4

15 mm Hg

Question 5

What is left atrium pressure?

Answer 5

8 mm Hg

Question 6

What is the pressure gradient in pulmonary system?

Answer 6

7 mm Hg

Question 7

What is the mean pressure in left atrium?

Answer 7

2 mm Hg

Question 8

Failure of the ___ side of the heart can cause pressure to build up in pulmonary circulation

Answer 8

left

Question 9

What is the physiologic shunt?

Answer 9

2% of the blood in the systemic arteries is blood that has bypassed the pulmonary capillaries, blood coming from the lung parenchyma and left side of the heart

Question 10

What happens in oxygen concentration in alveoli is 70% or more below normal?

Answer 10

adjacent blood vessels constrict

caused by unknown vasoconstriction

Question 11

how much blood flow is in zone 1

Answer 11

no blood flow; local alveolar capillary pressure never rises higher than alveolar air pressure

Question 12

how much blood flow is in zone 2

Answer 12

intermittent blood flow

Question 13

how much blood flow is in zone 3

Answer 13

continuous blood flow

Question 14

What are agents that constrict pulmonary arterioles?

Answer 14

norepinephrine
epinephrine
angiotensin II
some prostaglandins

Question 15

What agents dilate pulmonary arterioles?

Answer 15

isoporterenol

acetylcholine

Question 16

What agents that constrict pulmonary venules?

Answer 16

serotonin
histamine
e coli endotoxin

Question 17

Why does pulmonary arterial pressure rise only a little during maximum exercise?

Answer 17

because the number of open capillaries increases 3x and all capillaries distends and increases flow rate up to 2x

Question 18

What happens in left heart failure?

Answer 18

blood begins to dam up in left atrium
left atrial pressure raises from 1-5 mm Hg to 40-50 mm Hg
increases above 8 mm Hg cause increases in pulmonary arterial pressure
above 30 mm Hg, edema likely to develop

Question 19

pulmonary capillaries are relatively ______ to protein molecules

Answer 19

leaky

Question 20

When does pulmonary edema occur?

Answer 20

when pulmonary capillary pressure > 25 mm Hg

Question 21

What causes pulmonary edema?

Answer 21

left sided heart failure or mitral valve disease

damage to pulmonary blood capillary membranes: infections, breathing noxious substances

Question 22

What is pleural effusion?

Answer 22

edema of the pleural cavity

Question 23

What is the causes of pleural effusion?

Answer 23

blockage of lymphatic drainage from pleural cavity
cardiac failure
considerably reduced plasma colloid osmotic pressure
infection/inflammation

Question 24

Hypoxia increases pressure in the ____ artery due to what?

Answer 24

pulmonary; release of a prostaglandin

Question 25

What is the result of bronchial obstruction?

Answer 25

constriction of vessels supplying the poorly ventilated alveoli

Question 26

What causes bronchial obstruction?

Answer 26

due locally to low alveolar PO2 effect on the vessels
drop in pH due to accumulation of CO2
decline in pH produces vasoconstriction in pulmonary vessels
decline in pH produces vasodilation in other tissues

Question 27

What are the factors that affect rate of gas diffusion?

Answer 27

solubility of gas in fluid
cross sectional area of the fluid
distance through which the gas must diffuse
molecular weight of gas
temperature of fluid

Question 28

What is oxygen concentration in the alveoli and partial pressure controlled by?

Answer 28

rate of absorption of oxygen into the blood

rate of new oxygen entry into the lungs

Question 29

alveolar PCO2 increases in _____ proportion to rate of excretion

Answer 29

direct

Question 30

alveolar PCO2 decease in _____ proportion to alveolar ventilation

Answer 30

inverse

Question 31

What factors determine how rapidly a gas will pass through the respiratory membrane?

Answer 31

membrane thickness
membrane surface area
diffusion coefficient of gas in the substance of the membrane
partial pressure difference of gas between the two sides of the membrane

Question 32

What is the ventilation perfusion ratio?

Answer 32

Va/Q= alveolar ventilation/ blood flow

Question 33

Va/Q is normal when both factors are _______

Answer 33

normal for a given alveolus