Forces Driving the Movement of Gases- Part 1 Flashcards
contrast length, diameter, cross-sectional area, resistance to airflow, and airflow velocity moving from trachea to terminal airways
- diameter decreases
- length of airway segments decreases
- cumulative cross-sectional area increases
- lower airway resistance increases by a lot but the lower airways are so branched that this resistance is actually negligible
- in the lowest airways where resistance is technically very high, air flow velocity is very low
describe how the pressure gradient in airways and airway resistance affect the rate or velocity of air flow in and out of the lungs moving from the trachea to the terminal airways
define compliance, elastance, surface tension, and airway resistance and how each is related to the others; include the respiratory zones in which each has its affects; describe how each affects inhalation and deflation of the lungs
define compliance
how easy or hard it is for the lungs to stretch;
very compliant: big change in volume for a given change in pressure
low compliance: not much change in volume for a given change in pressure
inverse to elasticity; must be overcome for inhalation and exhalation
define elastance
how much the lungs want to/will recoil
pulmonary elasticity is due to elastin fibers that surround lower airways and help maintain shape, plus some collagen providing structural support
when the alveoli are distended, they want to return to their original shape, pulling lungs inward
this elastic force helps the recoil motion of exhalation (when distended at end of inhalation, want to snap lungs inward for exhalation)
describe surface tension
water molecules like to be together, so surface tension of alveoli tries to pull alveoli back inwards when distended at end of inhalation so water molecules can be together again
surface tension is reduced by surfactant, which is produced by type II alveolar cells, 85-90% lipids, and works to keep alveoli open instead of collapsing
