Physiology
Since atmospheric pressure is relatively constant, pressure in the lungs must be higher or lower than atmospheric pressure for air to flow between the atmosphere and the alveoli. It is nothing but the elastic recoiling of the lungs. If 'transpulmonary pressure' = 0 (alveolar pressure = intrapleural pressure), such as when the lungs are removed from the chest cavity or air enters the intrapleural space (a pneumothorax), the lungs collapse as a result of their inherent elastic recoil. Under physiological conditions the transpulmonary pressure is always positive; intrapleural pressure is always negative and relatively large, while alveolar pressure moves from slightly positive to slightly negative as a person breathes. For a given lung volume the transpulmonary pressure is equal and opposite to the elastic recoil pressure of the lung.
The transpulmonary pressure vs Volume curve of inhalation (usually plotted as Volume in function of Pressure) is different from that of exhalation, the difference being described as hysteresis. Lung volume at any given pressure during inhalation is less than the lung volume at any given pressure during exhalation.
Read more about this topic: Transpulmonary Pressure
Famous quotes containing the word physiology:
“The world moves, but we seem to move with it. When I studied physiology before ... there were two hundred and eight bones in the body. Now there are two hundred and thirty- eight.”
—Ellen Henrietta Swallow Richards (1842–1911)
“A physician’s physiology has much the same relation to his power of healing as a cleric’s divinity has to his power of influencing conduct.”
—Samuel Butler (1835–1902)
“I have more in common with a Mexican man than with a white woman.... This opinion ... chagrins women who sincerely believe our female physiology unequivocally binds all women throughout the world, despite the compounded social prejudices that daily affect us all in different ways. Although women everywhere experience life differently from men everywhere, white women are members of a race that has proclaimed itself globally superior for hundreds of years.”
—Ana Castillo (b. 1953)