Hemodynamics of vascular ‘waterfall’: is the analogy justified?

Badeer, Henry S.; Hicks, James W.

doi:10.1016/0034-5687(92)90060-a

Cited by 29 publications

(25 citation statements)

References 15 publications

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“…The idea of a siphon in giraffe seems to have originated from a brief report (Patterson and Warren, 1952), and has been supported, mainly by Badeer and colleagues, in several articles (Badeer, 1986;Badeer, 1988;Hicks and Badeer, 1989;Badeer and Hicks, 1992;Badeer, 1997). Goetz (Goetz, 1955), who in 1955 was the first to study giraffe blood pressures, encapsulated the idea by asking 'whether the left ventricle does provide the moving force unaided or whether it is assisted in its task by other mechanisms such as a peristaltic wave along the carotid artery or a siphon effect of the venous blood carrying down the jugular vein helping to 'elevate' the blood in the carotid artery' (Goetz and Budtz-Olsen, 1955).…”

Section: Discussionmentioning

confidence: 99%

“…The origin of these pressures is controversial. The controversy has been reviewed at least six times (Badeer, 1986;Seymour and Johansen, 1987;Pedley, 1987;Badeer, 1988;Badeer and Hicks, 1992;Seymour et al, 1993) and evaluated empirically five times using mechanical models (Holt, 1959;Hicks and Badeer, 1989;Pedley et al, 1996;Badeer, 1997;Seymour, 2000).…”

Section: Introductionmentioning

confidence: 99%

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The origin of mean arterial and jugular venous blood pressures in giraffes

Mitchell

Maloney

Mitchell

et al. 2006

Journal of Experimental Biology

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'tissue' pressure to the 'jugular' tube during pump flow produced the typical pressures found in the jugular vein in giraffe. Constriction of the lowest, 'jugular cuff', portion of the 'jugular' limb showed that the cuff may augment the orthostatic reflex during head raising. Except when all tubes were rigid, pressures were unaffected by a siphon.We conclude that mean arterial blood pressure in giraffes is a consequence of the hydrostatic pressure generated by the column of blood in the neck, that tissue pressure around the collapsible jugular vein produces the known jugular pressures, and that a siphon does not assist flow through the cranial circulation.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The origin of mean arterial and jugular venous blood pressures in giraffes

Mitchell

Maloney

Mitchell

et al. 2006

Journal of Experimental Biology

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“…In collapsible vessels, such as the reptilian post caval vein, vessel cross-sectional area is largely determined by P TRANS (Katz et al, 1969;Kresh and Noordergraaf, 1972;Moreno et al, 1970). When IAP exceeds CVP, P TRANS becomes negative, resulting in venous vessel collapse and an increase in the viscous resistance to blood flow (Badeer and Hicks, 1992) Unlike mammals, reptiles do not possess a muscular diaphragm. Crocodilians do possess a sheath of connective tissue that connects the liver to the body wall and creates separate thoracic and abdominal cavities (Grigg and Gans, 1993a;Hughes, 1973).…”

Section: Discussionmentioning

confidence: 99%

Terrestrial locomotion does not constrain venous return in the American alligator,Alligator mississippiensis

Munns

Hartzler

Bennett

et al. 2005

Journal of Experimental Biology

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SUMMARY The effects of treadmill exercise on components of the cardiovascular(heart rate, mean arterial blood pressure, central venous pressure, venous return) and respiratory (minute ventilation, tidal volume, breathing frequency, rate of oxygen consumption, rate of carbon dioxide production)systems and on intra-abdominal pressure were measured in the American alligator, Alligator mississippiensis, at 30°C. Alligators show speed-dependent increases in tidal volume and minute ventilation,demonstrating that the inhibition of ventilation during locomotion that is present in some varanid and iguanid lizards was not present in alligators. Exercise significantly increases intra-abdominal pressure; however,concomitant elevations in central venous pressure acted to increase the transmural pressure of the post caval vein and thus increased venous return. Therefore, despite elevated intra-abdominal pressure, venous return was not limited during exercise in alligators, as was the case in Varanus exanthematicus and Iguana iguana. Respiratory cycle variations in intra-abdominal pressure, central venous pressure and venous return indicate that, at high tidal volumes, inspiration causes a net reduction in venous return during active ventilation and thus may act to limit venous return during exercise. These results suggest that, while tonically elevated intra-abdominal pressure induced by exercise does not inhibit venous return,phasic fluctuations during each breath cycle may contribute to venous flow limitation during exercise.

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“…Large veins, such as the mammalian inferior vena cava or the lizard post caval vein, behave like collapsible tubes in which the cross-sectional area is largely a function of transmural pressure (Katz et al, 1969;Kresh and Noordergraaf, 1972;Moreno et al, 1970). When transmural pressure falls below zero, large alterations in vessel cross-sectional area occur, causing partial or complete collapse of the vessel and large increases in the viscous resistance to blood flow (Badeer and Hicks, 1992).…”

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confidence: 99%