Chapter 1: Structure and Function

Question 1

How thin is the thinnest part of the blood-gas barrier?

Answer 1

0.3 microns

Question 2

What is the total surface area of the blood-gas barrier?

Answer 2

50-100 square meters

Question 3

What percentage of the alveolar wall is occupied by capillaries?

Answer 3

Nearly 100%

Question 4

What happens if the pressure in the alveolar capillaries rises above physiologic levels?

Answer 4

Damage to the blood-gas barrier

Question 5

How does oxygen cross the blood-gas barrier?

Answer 5

Passive diffusion

Question 6

In diffusing from alveolus to hemoglobin, what layers does oxygen cross?

Answer 6

Surfactant -> epithelial cell -> interstitium -> endothelial cell -> plasma -> RBC membrane

Question 7

What is the formula for calculating PO2 (in mm Hg) of moist inspired air?

Answer 7

PO2 = fO2 x (Pa - PH2O)

PO2 = partial pressure of oxygen
fO2 = fraction of atmosphere comprised of oxygen = 0.21
Pa = atmospheric pressure (760 mm Hg at sea level, 608 mm Hg in Denver, 247 mm Hg on top of Mt. Everest)
PH2O = partial pressure of water vapor at 37C (in your lungs) = 47 mm Hg

Question 8

What is PO2 on top of Mt. Everest?

Answer 8

PO2 = 0.21 x (247 - 47) = 42 mm Hg

Question 9

What is the total volume of the conducting zone of the lungs?

Answer 9

150 mL

Question 10

What is another name for the conducting zone of the lungs?

Answer 10

Anatomic dead space

Question 11

What is the resting volume of the lungs?

Answer 11

About 3 L

Question 12

What capacity of air resides in the lungs at resting volume?

Answer 12

FRC - Functional Residual Capacity

Question 13

What does the resting state of the lungs represent, mechanically?

Answer 13

Balance between elastic recoil and resistance to collapse

Question 14

What physiological feature distinguishes terminal from respiratory bronchioles?

Answer 14

Walls of respiratory bronchioles have alveolar sacks

Question 15

How many branchings of the conducting airways are there before the appearance of alveoli?

Answer 15

16

Question 16

What is the predominant mode of gas flow in the alveolar ducts?

Answer 16

Diffusion, not convection (bulk flow)

Question 17

Which part of the pulmonary vasculature follows a pattern that branches with the airways?

Answer 17

Arterial side

Question 18

What is the average diameter of the capillaries in the lung?

Answer 18

7-10 microns, big enough for squeezing RBCs through

Question 19

Compare the volume of blood flow between the bronchial and pulmonary circulation

Answer 19

pulmonary&raquo_space; bronchial

Question 20

Into which vessels do the bronchial capillaries drain?

Answer 20

Some drains via the pulmonary veins, some enters systemic circulation

Question 21

Where does the bronchial circulation arise?

Answer 21

Arch of the aorta

Question 22

How much time does an RBC spend traversing the capillary networks of the pulmonary circulation?

Answer 22

0.75 seconds

Question 23

How many alveoli will an RBC visit while in the pulmonary circulation?

Answer 23

Two or three

Question 24

How many alveoli does the lung have in total?

Answer 24

~500 million

Question 25

What is the mean pressure in the pulmonary artery?

Answer 25

Typically 9-18 mm Hg

Question 26

What is the normal value of the pulmonary capillary wedge pressure (PCWP)?

Answer 26

Typically 6-12 mm Hg

Question 27

What is the PCWP supposed to represent?

Answer 27

Pressure in the left atrium

Question 28

What is the typical diameter of an alveolus?

Answer 28

0.3 mm

Question 29

Where are large particles filtered while breathing?

Answer 29

Nose (hair, Stokes parameter flow)

Question 30

What happens to small particles that deposit in the conducting airways of the lungs?

Answer 30

Particles stick to mucus, which is continually swept up and out of the airways by cilia past the epiglottis, where it is swallowed. Yuck.

Question 31

What happens to the smallest particles that deposit in the alveoli?

Answer 31

There are no cilia in the alveoli. Foreign material is engulfed by macrophages, which are subsequently removed from the lung via lymphatics or blood flow.