Describe the structure and function of the alveolus.
Better answers related structure to function. Many answers lacked key anatomical features (for
example pores of Kohn, basement membrane, interconnecting walls / alveolar
interdependence etc.). There was little understanding of the role and origin of the basement
membrane of the alveolus. Some candidates went into detailed discussions of Work of
Breathing, respiratory mechanics and the renin-angiotensin system which were not asked for.
Answers not reaching a pass mark generally suffered from lacking detail and suggested only a
superficial understanding of the area.
Though this resource is often at fault of being excessively critical of the college examiners, at one stage or another one must share in their exasperation, as to digress on the renin-angiotensin-aldosterone system would be extreme for even this digression-prone author.
Anyway. The college asked for the structure and function of the alveolus. It is possible to do this thing in a number of ways. One might first discuss the structure, and then the function:
Structure of the alveolus
Macroscopic characteristics:
Gas exchange surface
Cell types
Interstitial fibres and basal lamina
Function of the alveolus
Alternatively, it may be able to marry the two categories in a table which pairs the structures with whatever their function is supposed to be:
Structure |
Function |
Alveolar macrostructure: large number of (mostly spherical) air spaces connected by septa |
|
Alveolar blood-gas barrier: a thin trilamellar membrane composed of three layers:
|
Short diffusion distance: 0.2-2 µm for the blood-gas interface
|
Elastic basement membrane, containing the septal interstitial fibre network:
|
|
Type I alveolar cells: think cels with extended cytoplasmic plates which cover a large surface arrea |
|
Type II alveolar cells: |
|
Pores of Kohn: defects in alveolar septal walls |
|
Knudsen, Lars, and Matthias Ochs. "The micromechanics of lung alveoli: structure and function of surfactant and tissue components." Histochemistry and cell biology 150.6 (2018): 661-676.
Maina, John N., and John B. West. "Thin and strong! The bioengineering dilemma in the structural and functional design of the blood-gas barrier." Physiological reviews 85.3 (2005): 811-844.
Gil, J., et al. "Alveolar volume-surface area relation in air-and saline-filled lungs fixed by vascular perfusion." Journal of Applied Physiology 47.5 (1979): 990-1001.
Yamaguchi, Kazuhiro, et al. "Anatomical backgrounds on gas exchange parameters in the lung." World Journal of Respirology 9.2 (2019): 8-28.
Wangensteen, O. D., L. E. Wittmers Jr, and J. A. Johnson. "Permeability of the mammalian blood-gas barrier and its components." American Journal of Physiology-Legacy Content 216.4 (1969): 719-727.
Massaro, Gloria D., and Donald Massaro. "Formation of pulmonary alveoli and gas-exchange surface area: quantitation and regulation." Annual review of physiology 58.1 (1996): 73-92.
Klingele, TERENCE G., and NORMAN C. Staub. "Alveolar shape changes with volume in isolated, air-filled lobes of cat lung." Journal of Applied Physiology 28.4 (1970): 411-414.
Ward, H. E., and T. E. Nicholas. "Alveolar type I and type II cells." Australian and New Zealand journal of medicine 14 (1984): 731-734.
Weibel, Ewald R. "A note on differentiation and divisibility of alveolar epithelial cells." Chest 65.4 (1974): 19S-21S.
Crapo, James D., et al. "Cell number and cell characteristics of the normal human lung." American Review of Respiratory Disease 126.2 (1982): 332-337.
Gil, J., et al. "Alveolar volume-surface area relation in air-and saline-filled lungs fixed by vascular perfusion." Journal of Applied Physiology 47.5 (1979): 990-1001.
Schneeberger, E. E. "Barrier function of intercellular junctions in adult and fetal lungs." Pulmonary edema (1979): 21-37.
Gil, J. O. A. N., DENNIS A. Silage, and JUDITH M. McNIFF. "Distribution of vesicles in cells of air-blood barrier in the rabbit." Journal of Applied Physiology 50.2 (1981): 334-340.
Evans, Michael J., et al. "Renewal of alveolar epithelium in the rat following exposure to NO2." The American journal of pathology 70.2 (1973): 175.
Pastor, Luis Miguel, et al. "Morphogenesis of rat experimental pulmonary emphysema induced by intratracheally administered papain: changes in elastic fibres." Histology and histopathology (2006).
Bastacky, J., and J. Goerke. "Pores of Kohn are filled in normal lungs: low-temperature scanning electron microscopy." Journal of Applied Physiology 73.1 (1992): 88-95.
Boatman, E. S., and H. B. Martin. "Electron microscopy of the alveolar pores of Kohn." American Review of Respiratory Disease 88.6 (1963): 779-784.
Desplechain, C., et al. "The pores of Kohn in pulmonary alveoli." Bulletin europeen de physiopathologie respiratoire19.1 (1983): 59-68.
Weibel, Ewald R. "Lung morphometry: the link between structure and function." Cell and tissue research 367.3 (2017): 413-426.
Cordingley, J. L. "Pores of Kohn." Thorax 27.4 (1972): 433-441.
Terry, Peter B., and Richard J. Traystman. "The clinical significance of collateral ventilation." Annals of the American Thoracic Society 13.12 (2016): 2251-2257.
Reich, Stanley B., and Jacob Abouav. "Interalveolar air drift." Radiology 85.1 (1965): 80-86.
Kuriyama, T., and W. W. Wagner Jr. "Collateral ventilation may protect against high-altitude pulmonary hypertension." Journal of Applied Physiology 51.5 (1981): 1251-1256.