Chapter 1: Structure and Function Flashcards
How thin is the thinnest part of the blood-gas barrier?
0.3 microns
What is the total surface area of the blood-gas barrier?
50-100 square meters
What percentage of the alveolar wall is occupied by capillaries?
Nearly 100%
What happens if the pressure in the alveolar capillaries rises above physiologic levels?
Damage to the blood-gas barrier
How does oxygen cross the blood-gas barrier?
Passive diffusion
In diffusing from alveolus to hemoglobin, what layers does oxygen cross?
Surfactant -> epithelial cell -> interstitium -> endothelial cell -> plasma -> RBC membrane
What is the formula for calculating PO2 (in mm Hg) of moist inspired air?
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
What is PO2 on top of Mt. Everest?
PO2 = 0.21 x (247 - 47) = 42 mm Hg
What is the total volume of the conducting zone of the lungs?
150 mL
What is another name for the conducting zone of the lungs?
Anatomic dead space
What is the resting volume of the lungs?
About 3 L
What capacity of air resides in the lungs at resting volume?
FRC - Functional Residual Capacity
What does the resting state of the lungs represent, mechanically?
Balance between elastic recoil and resistance to collapse
What physiological feature distinguishes terminal from respiratory bronchioles?
Walls of respiratory bronchioles have alveolar sacks
How many branchings of the conducting airways are there before the appearance of alveoli?
16
What is the predominant mode of gas flow in the alveolar ducts?
Diffusion, not convection (bulk flow)
Which part of the pulmonary vasculature follows a pattern that branches with the airways?
Arterial side
What is the average diameter of the capillaries in the lung?
7-10 microns, big enough for squeezing RBCs through
Compare the volume of blood flow between the bronchial and pulmonary circulation
pulmonary»_space; bronchial
Into which vessels do the bronchial capillaries drain?
Some drains via the pulmonary veins, some enters systemic circulation
Where does the bronchial circulation arise?
Arch of the aorta
How much time does an RBC spend traversing the capillary networks of the pulmonary circulation?
0.75 seconds
How many alveoli will an RBC visit while in the pulmonary circulation?
Two or three
How many alveoli does the lung have in total?
~500 million
What is the mean pressure in the pulmonary artery?
Typically 9-18 mm Hg
What is the normal value of the pulmonary capillary wedge pressure (PCWP)?
Typically 6-12 mm Hg
What is the PCWP supposed to represent?
Pressure in the left atrium
What is the typical diameter of an alveolus?
0.3 mm
Where are large particles filtered while breathing?
Nose (hair, Stokes parameter flow)
What happens to small particles that deposit in the conducting airways of the lungs?
Particles stick to mucus, which is continually swept up and out of the airways by cilia past the epiglottis, where it is swallowed. Yuck.
What happens to the smallest particles that deposit in the alveoli?
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.
