Pulmonary Circulation

Question 1

What is the pathway of the high pressure, low flow circulation?

Answer 1

Thoracic aorta -> bronchial arteries

Trachea, bronchial tree, adventitia, CT

Question 2

What is the pathway of the low pressure, high flow?

Answer 2

Pulmonary artery and branches -> alveoli

Question 3

The wall thickness of the arterial artery is ___ that of the aorta.

Answer 3

1/3

Question 4

The wall thickness of the arterial artery is 1/3 that of the aorta. What effect does this have on compliance?

Answer 4

The pulmonary arterial tree has a larger compliance.

Question 5

What is the pulmonary arterial pressure?

Answer 5

24/9 mm Hg

Question 6

What is the mean pulmonary arterial pressure?

Answer 6

15 mm Hg

Question 7

What is the left atrium pressure?

Answer 7

8 mm Hg

Question 8

What are agents that constrict pulmonary arterioles?

Answer 8

Norepinephrine

Epinephrine

Angiotensin II

Some prostraglandins

Question 9

What are some agents that dilate pulmonary arterioles?

Answer 9

isoproterenol

Acetylcholine

Question 10

What are some agents that constrict pulmonary venules?

Answer 10

Serotonin

Histamine

E. coli endotoxin

Question 11

What do sympathetic vasoconstrictor nerve fibers affect blood outflow?

Answer 11

They decrease pulmonary blood flow by 30%. This mobilizes blood from pulmonary nerves.

Question 12

What effect does heavy exercise have on blood flow through the lungs and why does this cause minimal rise in pulomnary arterial pressure?

Answer 12

It increases blood flow through lungs by 4 - 7 times.

A minimal rise occurs because the number of capillaries opens up, and they are also distended (increases flow rate up to 2 times).

Question 13

How does failure of the left side of the heart affect pulmonary circulation?

Answer 13

Pressure builds up greatly.

Question 14

What zone of the lung has no blood flow?

Answer 14

Zone 1

In this zone, local alveolar capillary pressure never rises higher than alveolar air pressure.

Question 15

In which zone is there intermittent blood flow only during systole?

Answer 15

Zone 2

Question 16

In which zone is there continuuous blood flow?

Answer 16

Zone 3

Question 17

The apices of the lung has what type of flow?

Answer 17

Zone 2 flow (intermittent flow during systole)

Question 18

Lower areas of the lungs have what type of flow?

Answer 18

Zone 3 flow

Question 19

You have completed heavy exercise. How does the blood flow change through the lungs?

Answer 19

Blood flow in the apices is converted from zone 2 to zone 3 flow.

Question 20

Describe the hydrostatic and osmotic forces involved in lung capillary fluid exchange.

Answer 20

Hydrostatic and osmotic forces produce a mean filtration pressure of 1 mm Hg (29 - 28).

Colloid osmotic pressure in pulmonary interstitial tissue is about 14 mm Hg compared to less than 7 mm Hg in peripheral tissues.

Question 21

What are the most common causes of pulmonary edema?

Answer 21

Left-sided heart failure

Mitral valvue disease

Damage to pulmonary blood capillary membranes:
infections
breathing noxious substances.

Question 22

At what capillary pressure does a pulmonary edema occur?

Answer 22

Occurs when pulmonary capillary pressure > 25 mm Hg

Question 23

What might happen when capillary pressure remains chronically elevated for two weeks or more?

Answer 23

Compensation usually occurs by an increase in the lymphatic system, which carries excess fluid away.

Question 24

What are the causes of pleural effusion?

Answer 24

Blockage of lymphatic drainange from pleural cavity

cardiac failure

reduced plasma colloid osmotic pressure

Infection/inflammation

Question 25

If the pressure in the pleural space becomes positive, what happens to the lungs?

Answer 25

They tend to collapse

Question 26

Hypoxia increases pressure in the pulmonary artery. How does it cause increaesd pressure?

Answer 26

by the release of prostanglandins.

Question 27

What are the reults of bronchial obstruction and hypoxia in relation to blood flow?

Answer 27

Bronchial obstruction causes constriction of vessels. This is due to locally due to low alveolar PO2 effects on the vessels.

Question 28

During bronchial obstruction, what occurs to the pH?

Answer 28

It decreases.

This causes vasoconstriction in pulmonary vessels and vasoDILATION in other tissues.

Question 29

How does bronchial obstruction affect blood flow?

Answer 29

It is reduced in a portion of the lung. Alveolar PCO2 is lowered, resulting a constriction of the bronchi supplying that portion of the lung.

Question 30

What are the two circulations of the lung?

Answer 30

High pressure, low flow

Low pressure, high flow