title: [The oxygen pathway: how well-built is the respiratory system?].
abstract: The question is explored of how the structural systems that constitute the pathway for oxygen from the air through the lung and the circulation of blood to the mitochondria in muscle cells affect the O2 flow rate, and whether their quantitative structural characteristics conform to the hypothesis of symmorphosis which postulates a match of structural design to overall functional demand. By combining physiological and morphometric studies, it is first demonstrated that the diffusing capacity of the human lung is slightly larger than that needed for maximal O2 uptake. Comparative studies of small and large species (from the mouse to the cow) and of athletic and sedentary species pairs (such as horses and cows) show that the design parameters of muscle cells and their mitochondria, of the capillaries, and of blood and circulation are coadjusted to O2 demand by the muscles during exercise. In contrast, the lung is only partially adjusted to this level of demand, a fact which may be related to the slight excess capacity of its gas exchanger. In the organ that forms the interface to the environment this may be a desirable safety factor.
authors.affiliation: Anatomisches Institut, Universität Bern.
authors.forename: E R
authors.initials: ER
authors.lastname: Weibel
mesh_terms: D000818:Animals; D002417:Cattle; D006321:Heart / Q000502:physiology; D006801:Humans; D008168:Lung / Q000098:blood supply / Q000502:physiology*; D051379:Mice; D008931:Mitochondria, Muscle / Q000378:metabolism; D010100:Oxygen / Q000502:physiology*; D010101:Oxygen Consumption; D011650:Pulmonary Alveoli / Q000648:ultrastructure; D011652:Pulmonary Circulation; D011653:Pulmonary Diffusing Capacity; D011659:Pulmonary Gas Exchange
chemical_list: D010100:Oxygen
vernacular_title: Der Fliesspfad für Sauerstoff: Wie gut ist das Atmungssystem gebaut?