Abstract
Abstract Eight normal human lungs, obtained from patients dying of causes not involving the lung. were totally fixed in situ by instillation of a glutaraldehyde solution into the airways shortly post mortem. The age range was 19–40 years, average body weight was 74 kg and the average lung volume 4300 ml. Stratified random samples from twelve regions were morphometrically studied by electron microscopy using stereological methods. The fine structure of the human lung parenchyma as seen by scanning and transmission electron microscopy is described. The alveolar surface area was found to be 143 m2 on the average (± 12); this value is 75% higher than previous light microscopic estimates mainly because of higher resolution of the electron microscope thus leading to a different definition of ‘alveolar surface’. Capillary surface area and volume were 126 m2 (±12) and 213 ml (± 31), respectively. The arithmetic mean thickness of the human air-blood tissue barrier was estimated at 2.2 μm (±0.19) and is thus considerably thicker than that found in other mammals: the same holds for the harmonic mean thickness of the barrier (0.62 μ±0.04). This appears to be related to a particularly large amount of connective tissue fibers found in the human alveolar septum. From this morphometric information total pulmonary diffusion capacity for 02 was calculated; using the set of largest and smallest physical coefficients we obtained respectively a maximal value, D L max = 263 ml O 2 /min ·mm Hg (±34) , and a minimal value, D L min = 125 (± 18) . These data relate to the totally inflated and unfolded lung; if they are corrected to account for ‘available’ gas exchange surface, reduced because of the presence of an alveolar extracellular lining, we obtain for ‘available’ diffusion capacity : D L max * = 130–190 and D L min * = 62–91 ml O 2 /min·mm Hg respectively. These corrected values seem to agree with physiological estimates of human dl in exercise.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
