Measurement of the distensibility of the parabronchi in duck lungs

Macklem, Peter T.; Bouverot, P; Scheid, P.

doi:10.1016/0034-5687(79)90004-5

Cited by 59 publications

(43 citation statements)

References 7 publications

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“…contribute to and explain the exceptional strength that has been reported in the avian lung by Macklem et al (1979), Powell et al (1985), and West et al (2007). The structural proximity between the lungs of the Ostrich, a bird from a taxon (ratite) considered to be the most primitive among birds (King and Farner, 1969;Storer, 1971a,b;Calder and Dawson, 1978), with those of the passerine birds (the most derived avian taxon) (Sibley and Alhquist, 1990;Barker et al, 2004), shows exceptional respiratory refinements for a nonvolant, supposedly primitive bird.…”

Section: Computer Reconstruction Of Parabronchus Of Ostrichmentioning

confidence: 89%

Three‐Dimensional Serial Section Computer Reconstruction of the Arrangement of the Structural Components of the Parabronchus of the Ostrich, Struthio Camelus Lung

Maina

Woodward

2009

The Anatomical Record

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The Ostrich, Struthio camelus is the largest extant bird. The arrangement of the airway and the vascular components of the parabronchus of its lung were investigated by 3D serial section reconstruction. Modestly developed atrial muscles, shallow atria, paucity of infundibulae with preponderant origination of the air capillaries (ACs) from the atria and lack of interparabronchial septa, structural features that epitomize lungs of most highly derived metabolically active volant birds were observed. Intertwined very closely, the ACs and the blood capillaries (BCs) are not straight, blindended tubules that run in contact, counter and parallel to each other as has been claimed and/or modeled. Crosscurrent (perpendicular ¼ orthogonal) orientation between the centripetal (inward) flow of the venous blood (VB) from the periphery of the parabronchus and the flow of air in the parabronchial lumen occur. Also, a countercurrent-like arrangement between the ACs which convey air centrifugally (outwards ¼ radially) and the BCs that transport venous blood centripetally (inwards) was identified. The VB is conveyed to the parabronchus by the interparabronchial arteries and delivered to the exchange tissue by the intraparabronchial arterioles: it is then arterialized at the infinitely many points where the ACs and the BCs contact. Functionally, the crosscurrent arrangement grants a multicapillary serial arterialization arrangement which extends the time that the respiratory media, air and blood, are exposed to each other. The contribution that the countercurrent-like arrangement makes to the gas exchange process remains obscure.

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Section: Computer Reconstruction Of Parabronchus Of Ostrichmentioning

confidence: 89%

Three‐Dimensional Serial Section Computer Reconstruction of the Arrangement of the Structural Components of the Parabronchus of the Ostrich, Struthio Camelus Lung

Maina

Woodward

2009

The Anatomical Record

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“…Although accounts on the remarkable strengths of the ACs and the blood capillaries (BCs) of the avian lung have been in the scientific domain for about three decades (Macklem et al 1979;Powell et al 1985), until recently, only cursory references and speculations existed on this interesting property, which has now been sufficiently corroborated by, for example, Wideman (2001), West et al (2007a), and Watson et al (2008). The particular structures and ⁄ or mechanisms that can explain this property have remained obscure and contentious.…”

Section: Discussionmentioning

confidence: 99%

“…One of the most confounding properties of the functional design of the avian respiratory system concerns the remarkable strengths of the minuscule terminal respiratory units, the air capillaries (ACs) and the blood capillaries (BCs) of the lung. About three decades ago, Macklem et al (1979) reported that the ACs remained open when the lung was subjected to a positive pressure of 20 cm H 2 O (2 kPa). They remarked that 'unknown factors serve to confer a remarkable stability on these fine structures'.…”

Section: Introductionmentioning

confidence: 99%

Implicit mechanistic role of the collagen, smooth muscle, and elastic tissue components in strengthening the air and blood capillaries of the avian lung

2010

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To identify the forces that may exist in the parabronchus of the avian lung and that which may explain the reported strengths of the terminal respiratory units, the air capillaries and the blood capillaries, the arrangement of the parabronchial collagen fibers (CF) of the lung of the domestic fowl, Gallus gallus variant domesticus was investigated by discriminatory staining, selective alkali digestion, and vascular casting followed by alkali digestion. On the luminal circumference, the atrial and the infundibular CF are directly connected to the smooth muscle fibers and the elastic tissue fibers. The CF in this part of the parabronchus form the internal column (the axial scaffold), whereas the CF in the interparabronchial septa and those associated with the walls of the interparabronchial blood vessels form the external, i.e. the peripheral, parabronchial CF scaffold. Thin CF penetrate the exchange tissue directly from the interparabronchial septa and indirectly by accompanying the intraparabronchial blood vessels. Forming a dense network that supports the air and blood capillaries, the CF weave through the exchange tissue. The exchange tissue, specifically the air and blood capillaries, is effectively suspended between CF pillars by an intricate system of thin CF, elastic and smooth muscle fibers. The CF course through the basement membranes of the walls of the blood and air capillaries. Based on the architecture of the smooth muscle fibers, the CF, the elastic muscle fibers, and structures like the interparabronchial septa and their associated blood vessels, it is envisaged that dynamic tensional, resistive, and compressive forces exist in the parabronchus, forming a tensegrity (tension integrity) system that gives the lung rigidity while strengthening the air and blood capillaries.

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“…Lung volumes at 0 cm H 2 O (kPa) were assumed to be representative of that at the start of a penguin's dive because the avian lung is considered relatively rigid, with the lung of the duck changing less than 2% in volume during spontaneous respiration (Macklem et al, 1979). As we had hypothesized, mass-specific lung volume was least in the deepest-diving species, although differences in mean mass-specific lung volumes were only significant between Adélie and emperor penguins (Table 1).…”

Section: Lung Volumementioning

confidence: 99%

Penguin lungs and air sacs: implications for baroprotection, oxygen stores and buoyancy

Ponganis

Leger

Scadeng

2015

Journal of Experimental Biology

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The anatomy and volume of the penguin respiratory system contribute significantly to pulmonary baroprotection, the body O 2 store, buoyancy and hence the overall diving physiology of penguins. Therefore, three-dimensional reconstructions from computerized tomographic (CT) scans of live penguins were utilized to measure lung volumes, air sac volumes, tracheobronchial volumes and total body volumes at different inflation pressures in three species with different dive capacities [Adeĺie (Pygoscelis adeliae), king (Aptenodytes patagonicus) and emperor (A. forsteri) penguins]. Lung volumes scaled to body mass according to published avian allometrics. Air sac volumes at 30 cm H 2 O (2.94 kPa) inflation pressure, the assumed maximum volume possible prior to deep dives, were two to three times allometric air sac predictions and also two to three times previously determined end-of-dive total air volumes. Although it is unknown whether penguins inhale to such high volumes prior to dives, these values were supported by (a) body density/buoyancy calculations, (b) prior air volume measurements in free-diving ducks and (c) previous suggestions that penguins may exhale air prior to the final portions of deep dives. Based upon air capillary volumes, parabronchial volumes and tracheobronchial volumes estimated from the measured lung/airway volumes and the only available morphometry study of a penguin lung, the presumed maximum air sac volumes resulted in air sac volume to air capillary/ parabronchial/tracheobronchial volume ratios that were not large enough to prevent barotrauma to the non-collapsing, rigid air capillaries during the deepest dives of all three species, and during many routine dives of king and emperor penguins. We conclude that volume reduction of airways and lung air spaces, via compression, constriction or blood engorgement, must occur to provide pulmonary baroprotection at depth. It is also possible that relative air capillary and parabronchial volumes are smaller in these deeper-diving species than in the spheniscid penguin of the morphometry study. If penguins do inhale to this maximum air sac volume prior to their deepest dives, the magnitude and distribution of the body O 2 store would change considerably. In emperor penguins, total body O 2 would increase by 75%, and the respiratory fraction would increase from 33% to 61%. We emphasize that the maximum pre-dive respiratory air volume is still unknown in penguins. However, even lesser increases in air sac volume prior to a dive would still significantly increase the O 2 store. More refined evaluations of the respiratory O 2 store and baroprotective mechanisms in penguins await further investigation of species-specific lung morphometry, start-of-dive air volumes and body buoyancy, and the possibility of air exhalation during dives.

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Measurement of the distensibility of the parabronchi in duck lungs

Cited by 59 publications

References 7 publications

Three‐Dimensional Serial Section Computer Reconstruction of the Arrangement of the Structural Components of the Parabronchus of the Ostrich, Struthio Camelus Lung

Three‐Dimensional Serial Section Computer Reconstruction of the Arrangement of the Structural Components of the Parabronchus of the Ostrich, Struthio Camelus Lung

Implicit mechanistic role of the collagen, smooth muscle, and elastic tissue components in strengthening the air and blood capillaries of the avian lung

Penguin lungs and air sacs: implications for baroprotection, oxygen stores and buoyancy

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