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Respiratory System (Pulmonary Ventilation (Pressure relationships in the…
Respiratory System
Pulmonary Ventilation
Direction gases move: Mechanical processes that depends on volume changes in thoracic cavity
- Volume changes lead to pressure changes
- Pressure changes lead to flow of gases to equalize pressure
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Boyle's law: relationship between pressure and volume of a gas
- Gases always fill the container they are in
- If amount of gas is the same and container size is reduced, pressure will increase
- Pressure (P) varies inversely with volume (V)
- Mathematically: P1V1=P2V2
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Respiratory volumes
Inspiratory reserve volume (IRV): amount of air that can be inspired forcibly beyond the tidal volume (2100-3200 mL)
Expiratory reserve volume (ERV): amount of air that can be forcibly expelled from lungs (1000-1200 mL)
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Residual volume (RV): amount of air that always remains in the lungs, needed to keep alveoli open
Respiratory Capacities
Total Lung Capacity (TLC): Maximum amount of air contained in lungs after a maximum inspiratory effort (TLC= TV+IRV+ERV+RV)
Vital Capacity (VC): Maximum amount of air that can be expired after a maximum inspiratory effort: (VC=TV+IRV+ERV)
Inspiratory Capacity (IC): Maximum amount of air that can be inspired after a normal tidal volume expiration (IC= TV+IRV)
Functional Residual Capacity (FRC): Volume of air remaining in the lungs after a normal tidal volume expiration (FRC=ERV+RV)
Two Zones
Conducting Zone: consists of the nose, pharynx, larynx, bronchi, and bronchioles. these structures form a continuous passageway for air to move in and out of the lungs
Respiratory Zone: begins where terminal bronchioles feed into respiratory bronchioles, which lead into alveolar ducts and finally into alveolar sacs. these thin-walled structures allow inhaled oxygen to diffuse into the lung capillaries In exchange for carbon dioxide
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Alveolar Ventilation Rate: flow of gases into and out of alveoli during a particular time (AVR=Frequency x (TV-dead space))
Internal Respiration
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The partial pressure and diffusion gradients are reversed from the situation for external respiration and pulmonary gas exchange
Tissue PCO2 is always higher than arterial blood (45mmHg vs 40mmHg), so CO2 moves from tissues into blood
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Tissue PO2 is always lower than in arterial blood (40mmHg vs 100mmHg), so oxygen moves from blood to tissues
Gas exchanges that occur between blood and alveoli and between blood and tissue cells take place by simple diffusion. They are driven by the partial pressure gradients of O2 and CO2 that exist on the opposite sides of the exchange membranes
Haldane Effect
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the lower the PO2, the more CO2 can bind to hemoglobin and form carbaminohemoglobins
Bohr Effect
At tissues, as more CO2 enters blood, more O2 dissociates from hemoglobin, more CO2 can bind to hemoglobin and form caraminohemoglobin
Henry's Law
at equilibrium, partial pressures in the two phases will be equal
Amount of each gas that will dissolve depends on:
Solubility: CO2 is 20x more soluble in water than O2, and little N2 will dissolve
Temperature: as temperature of liquid rises, solubility decreases
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External Respiration
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pulmonary gas exchange
O2 is being taken into the blood that flows through the pulmonary circuit to be distributed by systems arteries to body tissues
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