Respiratory Physiology Flashcards
What is the difference between intra-alveolar pressure & intra-pleural pressure?
-Intra-alveolar pressure: pressure within the alveoli
-Intra-pleural pressure: pressure exerted outside the lungs within the thoracic cavity (756 mm Hg at rest)
What keeps the lungs stretched apart?
-Intrapleural fluid cohesiveness
-Transmural pressure gradient: intra-alveolar pressure is great than intrapleural pressure (expands the lungs)
-Similar gradient exists across the thoracic wall which keep the thoracic cavity compressed
How does air flow into and out of the lungs?
Changes in the intra-alveolar pressure brought by respiratory muscle activity
What is Boyle’s Law? How does this relate to inspiration and expiration?
-At any constant temperature, the pressure exerted by a gas varies inversely with the volume of gas
-As the volume of gas increases, the pressure exerted by the gas decreases proportionately
-Respiratory muscle do not act directly on the lung of to affect volume; they affect the volume of the thoracic cavity, which in turn affects the volume of the lung by their cohesive interaction
What branch of the ANS controls bronchoconstriction? Bronchodilation?
-Parasympathetic=bronchoconstriction
-Sympathetic=bronchodilation
What is alveolar surface tension? What is its function? Why do we need it?
-Tension or force exerted by the H2O molecules on the alveolar surface
-Tendency is to oppose the expansion of the alveoli
-Reduces the size of the alveolus
-Results in elastic recoil
-However, too high of a surface tension would
-Collapse the lung
-Low compliance= hard to inflate and stretch
-So you need some surface tension but not too much
How do the pulmonary arterioles respond to decreased levels of oxygen? Is this different from systemic arterioles?
-Increase in CO2 induce bronchodilation of airway smooth muscles which increase airflow while decrease in O2 level induce vasoconstriction of the pulmonary arterioles, which decreases blood flow, allowing more O2 transfer between the lungs and capillaries
-Yes; systematic arterioles vasodilate in response to low O2 levels to increase blood flow to the tissues that it supplies
What is pulmonary surfactant? What cells secrete it?
Lipid and protein secretion from Alveolar type II cells
What is the difference between obstructive and restrictive lung disease?
-Obstructive lung disease: more difficulty emptying the lungs than filling them (Residual Volume goes up)
-Restrictive lung disease: lungs less compliant and can’t expand (Reduced VC- decreased)
What is dead-space volume?
Amount of air in the conducting pathways not available for gas exchange
Define partial pressure
The individual pressure exerted independently by a particular gas within a mixture of gases
What factors influence gas diffusion?
Surface area
Thickness of barrier
Diffusion of coefficient of gas
How is oxygen transported in the blood?
-Dissolved: very little amount is directly proportional to the PO2 of blood= PO2 of 100mm Hg=3ml O2 liter of blood
-Bound to hemoglobin: 98.5% of O2 transported; Reduced Hb-no bound oxygen; Oxyhemoglobin (HbO2)=bound to oxygen
What is the law of mass action?
A reversible reaction is determined by the concentration of the molecule involved
What does the oxygen Hb dissociation curve tell us?
Plateau portion:
-Exists at pulmonary capillaries where O2 is being loaded onto Hb
-At PO2 = 100 mm Hg = % Hb saturation = 97.5%
-Large changes in PO2 do not affect % Hb saturation = blood is carrying more than enough O2 to meet tissue demands
Steep Portion:
-Exists in systemic capillaries = PO2 is between 0 and 60 mm Hg
-O2 dissociates from Hb to flow down its gradient into the tissues
-Allows massive amounts of O2 to be “dropped” off when tissue demands increase
