Lecture 3 Flashcards
Breath
Inspiration and subsequent exhalation
Airflow
rate at which gas moves; varies b/w species; results from thoracic volume increasing, making pleural pressure more negative and pressure gradient drives air into the lungs
Flow of airflow stops when
volume is at a greater level at rest; pleural pressure is more negative and alveolar pressure is 0
Inflation
resistance of airflow makes pleural pressure more negative
End of Inspiration
pleural pressure is more negative than at rest due to stretch of the lungs by increasing volume and the lungs want to collapse
Pressure increases as…
volume increases and lungs want to collapse more
Compliance
measure of strech-ability of the lungs
2 major collapsing forces of the lungs
lung elastic recoil
surface tension
Surface Tension
force that acts at as gas-liquid interface which reduces the surface area of the interface
Air surrounded by liquid
surface tension acts to reduce area of air-liquid interface by collapsing the air bubble (pressure in air bubble counteracts the collapsing force)
Laplace Law
describes pressure required to keep bubble open; smaller radius and greater pressure required
P= 2t(surface tension)/r
Surfactant
substance that works to reduce air-liquid interface surface tension; produced by type 2 alveolar cells; keeps lung DRY
AS lung expands
surfacant layer thins and surface tension increases, greater collapsing force with increasing lug expansion
AS lung deflates
surfactant layer thickens and surface tension decreases- preventing collapse of the alveoli at low lung volumes
Consequences of surfactant insufficiency
lungs cant expand easily, muscles work harder
small alveoli collapse into larger alveoli
transduction of fluid into alveoli
