Ch.17
Terms
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- Atmospheric pressure (Patm)
- the pressure of the outside air; normal is 760 mmHg
- Intra-alveolar pressure
- ________-________ __________ is determined by the quantity (moles) of air molecules in the alveoli & the volume of alveoli themselves.
- Intrapleural pressure
- the pressure inside the pleural space
- Transpulmonary pressure
- the difference btwn the interpleural pressure & the intra-alveolar pressure
- functional residual capacity
- When the lungs are at rest all breathing muscles are relaxed, and the volume of air in the lungs under these conditions is called __________ _________ _________.
- Pneumothorax
-
air in the interpleural space
when air gets into interpleural space the suction is lost and the lung recoils or collapses. - Inspiration
-
contraction of the diaphram causes it to flatten & move downward
Meanwhile, contraction of the obliquely oriented external intercostals causes the ribs to pivot upward & outward, expanding the chest wall. - Expiration
- As the chest wall and lungs recoil, the volume of the lungs decrease causing alveolar pressure to increase to greater than atmospheric pressure.
-
1. the pressure gradient btwn the atmosphere & alveoli
2. airway resistance - The rate at which air flows into or out of the lungs is determined by 2 factors:
- compliance
- A measure of the EASE w/which they can be stretched.
- Lung compliance
- depends on the elasticity of the lungs, and on the surface tension of the fluid lining the alveoli.
- surface tension
- The greater the _______ _______, the more work needed to spread the fluid out.
- air-liquid interface
- The surface tension of the lungs is caused by the __________ ________ formed by the thin layer of fluid lining the internal surface of the alveoli.
- fluid layer
- As the lung expands, so does the _______ ______ in the alveoli.
- work
- As the lungs expand, _____ is required not only to stretch the elastic tissue but also to increase the surface area of the fluid layer.
- decrease
- The surface tension acts to _________lung compliance.
- pulmonary surfactant
- a detergent like substance that decreases the surface tension in the alveoli.
- type II alveolar cells
- secretes pulmonary surfactant which are located in the walls of alveoli
- airway resistance
-
the resistance of the entire system of airways in the respiratory tract
it is analogous w/ total peripheral resistance in cardiovascular physiology. - radius
- As _______ decreases, airway resistance increases.
- transpulmonary
- The increase in ____________ pressure that occurs during inspiration pulls outward on the airways, causing them to distend, which decreases resistance as inspiration continues.
-
expiration
decreases - During __________, the transpulmonary pressure _________, which reduces the distending force on airways and allows them to contract, thereby increasing the resistance.
-
Sympathetic stimulation
bronchodilation
Parasympathetic - __________ stimulation causes relaxation of the smooth muscles and increases the radius of bronchioles (called ____________), whereas _____________stimulation causes contraction of the smooth muscle and bronchoconstriction.
- Epinephrine
- __________ released from the adrenal medulla during sympathetic stimulation also causes bronchodilation.
- Histamine
- __________ causes contraction of the smooth muscle, resulting in bronchoconstriction.