Respiratory High Yield Concepts Flashcards
The primary responsibility of the lungs is…
exchange gas
What processes must be functioning for optimal gas exchange?
Ventilation → getting gas to the alveoli
Perfusion → removing gas from the alveoli by the blood
Diffusion → getting gas across alveolar walls
Control of breathing → regulating gas exchange
The airways consist of…
a series of branching tubes which become narrower, shorter, and more numerous as they penetrate deeper into the lung
Conducting zone
no alveoli
trachea, bronchi, bronchioles
Respiratory Zone
alveoli
respiratory bronchioles. alveolar ducts and sacs
There are ___ alveoli in lungs creating a total surface area of about ___
300 million
75 m2
Define: Alveoli
small, thin-walled inflatable air sacs encircled by pulmonary capillaries
has a single layer of thin exchange epithelium and is the site of gas exchange
air flows between adjacent alveoli via pores of Kohn
What are the 3 types of cells in alveoli?
Type I alveolar cells
Type II alveolar cells
Alveolar macrophages
Define: Type I alveolar cells
very thin, allowing gas exchange
Define: Type II alveolar cells
thicker
secrete surfactant to ease lung expansion
Define: Alveolar Macrophages
protect and defend
Atmospheric Pressure (PB)
760 mmHg at sea level
decreases as altitude increases
Intra-alveolar pressure (PA)
will equilibrate with atmospheric pressure
Intrapleural Pressure (Pip)
756 mmHg
recoil forces create a vacuum (“-4”)
closed cavity
Transmural Pressure (PL)
pressure across the lungs (PA - Pip)
key to inflating lungs
___ and __ hold the lungs and thoracic wall in tight apposition even though the lungs are smaller
Intrapleural fluid’s cohesiveness and the transmural pressure gradient (most important)
PA = 760 mmHg, pushes out vs. Pip of 756 mmHg
PB = 760 mmHg, pushes in vs. Pip
Why does the pleural space have slightly negative pressure?
because the chest is pulling out, lungs are pulling in, and there’s no extra fluid to fill expanded space
Pneumothorax
air enters pleural cavity, pressure equalizes with atmospheric pressure, transmural pressure gradient is gone, lungs collapse, thoracic wall springs out
Boyle’s Law
describes the relationship between the pressure and volume of a gas
as volume decreases, pressure increases
P1V1 = P2V2
changes in volume of chest cavity during ventilation cause pressure gradients
An increase in chest volume causes..
a decrease in pressure
air moves into the lungs from the atmosphere
A decrease in chest volume causes…
an increase in pressure, air moves out from body
Inspiration results from…
the contraction of the diaphragm and intercostal muscles (an active process)
the rib cage swings upwards and outwards
the enlarged cavity housing the lungs undergoes a pressure reduction with respect to the pressure existing outside the body
Expiration results from…
the relaxation of the diaphragm and intercostal muscles (a passive process)
The rib cage moves inward and downwards
The elastic recoil of the lungs creates a higher intra-alveolar pressure compared to atmospheric pressure that forces air out of the lungs
Laminar Airflow
low flow rate
usually in small airways