Assertion: respiratory tract | /r/HasProperty | open
Facets:
value: in health
type: OTHER
value: always
type: DEGREE
Source sentences:
text: In health these airways (starting at the nose or mouth, and ending in the microscopic dead-end sacs called alveoli) are always open, though the diameters of the various sections can be changed by the sympathetic and parasympathetic nervous systems.
text: Assuming the airway is open, air from the external environment then follows its pressure gradient down and expands the alveoli of the lungs, where gas exchange with the blood takes place.