The Caval Sphincter in Phoca vitulina L.

Harrison, R. J.; Tomlinson, Joanna; Bernstein, L.

doi:10.1038/173086b0

Cited by 7 publications

(7 citation statements)

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“…It is known that marine mammals dramatically redistribute cardiac output during dives (Bryden and Molyneux, 1978;Elsner, 1969;Harrison et al, 1954;Irving, 1938Irving, , 1939Kooyman, 1985;Whittow, 1987). While oxygen sensitive tissues, such as the central nervous system, maintain continuous blood flows during a dive, other organs are subjected to reduced blood flows, or temporary but complete blood flow cessation (e.g., Harrison et al, 1954;Irving, 1938Irving, , 1939Ridgway, 1960, 1983;Kanwisher and Sundes, 1965;Kooyman, 1972Kooyman, ,1985Kooyman et al, 1981;Zapol et al, 1979).…”

Section: Potential Limits To Convective Heat Loss: Circulatory Changementioning

confidence: 96%

“…While oxygen sensitive tissues, such as the central nervous system, maintain continuous blood flows during a dive, other organs are subjected to reduced blood flows, or temporary but complete blood flow cessation (e.g., Harrison et al, 1954;Irving, 1938Irving, , 1939Ridgway, 1960, 1983;Kanwisher and Sundes, 1965;Kooyman, 1972Kooyman, ,1985Kooyman et al, 1981;Zapol et al, 1979). For example, blood flow rates to the splanchnic beds of non-pregnant Weddell seals (Leptonychotes weddelli) can be reduced by more than 90% during forced dives (Zapol et al, 1979).…”

Section: Potential Limits To Convective Heat Loss: Circulatory Changementioning

confidence: 97%

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Functional morphology of the vascular plexuses associated with the cetacean uterus

1993

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The cetacean reproductive system is surrounded by thermogenic locomotory muscle and insulating blubber. This arrangement suggests elevated temperatures at the uterus that could induce detrimental effects on fetal development. We present anatomical evidence for a complex countercurrent heat exchange system that could function to regulate the thermal environment of the uterus and a developing fetus. Cooled venous blood from the surfaces of the dorsal fin and flukes enters the abdominal cavity via the lumbo-caudal venous plexus. This plexus is juxtaposed to the arterial and venous plexuses associated with the uterus. The morphology of the lumbo-caudal venous plexus suggests that it acts as a "heat sink" for the adjacent tissues. Heat may be transferred to the cool, lumbo-caudal venous plexus from the warm blood in the arterial and venous plexuses supplying the uterus. Heat may also be transferred from adjacent locomotory muscles to the cool lumbo-caudal venous plexus. The countercurrent heat exchanger created by the juxtaposition of the lumbo-caudal venous plexus with the uterovarian arterial plexus is similar in design to that of the countercurrent heat exchanger described for male cetaceans. The functional implications of introducing cool superficial blood into the abdominal cavity of a diving, and locomoting female cetacean are discussed.

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Section: Potential Limits To Convective Heat Loss: Circulatory Changementioning

confidence: 96%

Section: Potential Limits To Convective Heat Loss: Circulatory Changementioning

confidence: 97%

Functional morphology of the vascular plexuses associated with the cetacean uterus

1993

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“…Marine mammals can dramatically redistribute cardiac output during dives (Bron et al, 1966;Bryden and Molyneux, 1978;Elsner et al, 1966;Elsner and Gooden, 1983;Harrison et al, 1954;Harrison andTomlinson, 1956, 1963;Hol et al, 1975;Irving, 1969;Kooyman, 1985). Oxygen and temperature sensitive tissues, such as the central nervous system, maintain continuous blood flows during a deep dive, while other organs may be subjected to reduced blood flows, or temporary but complete blood flow cessation (Harrison et al, 1954;Irving, 1969;Irving et al, 1942;Ridgway, 1960, 1983;Kanwisher and Sundes, 1965;Kooyman, 1972Kooyman, , 1985Scholander et al, 1942;Kooy-man et al, 1981;Zapol et al, 1979). Seals thus may experience episodic decreases in blood flow to their splanchnic beds, for example blood flow rates to the splanchnic beds of non-pregnant Weddell seals (Leptonychotes weddelli) can be reduced by more than 90% during forced dives (Elsner et al, 1970;Zapol et al, 1979).…”

Section: Female Reproductionmentioning

confidence: 99%

Venous structures associated with thermoregulation of phocid seal reproductive organs

et al. 1995

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“…If pinnipeds remain in zone 3, as hypothesized, sphincter use is likely continual. Further, their sphincter controls the volume loss from the hepatic sinus (Elsner et al, 1971;Harrison et al, 1954;Hol et al, 1975;Nordgarden et al, 2000;Ronald et al, 1977;Thornton et al, 2001) and this may explain why the pinniped sphincter is well developed, particularly in phocids. Cetaceans lack the hepatic sinus.…”

Section: Use Of the Caval Sphincter May Differ In Cetaceans And Pinnimentioning

confidence: 99%

“…Sphincters have been observed in two relatively fastswimming odontocetes, the harbour porpoise (Barnett et al, 1958;Harrison and Tomlinson, 1956;Hilton and Gaskin, 1978) and bottlenose dolphin (Slijper, 1962), but they are thought either absent or functionally inadequate in the slower swimming fin and sei rorquals (Barnett et al, 1958;Harrison and Tomlinson, 1956;Slijper, 1962). Contraction of the sphincter inhibits caval flow (Elsner et al, 1971;Harrison et al, 1954;Hol et al, 1975), and it has been hypothesized that the sphincter protects the heart from flow overload when venous return is augmented by elevated abdominal pressures (Harrison and Tomlinson, 1956). If this is the case, we wonder why the sphincter should be present in some cetaceans but absent in others.…”

Section: Introductionmentioning

confidence: 99%

The caval sphincter in cetaceans and its predicted role in controlling venous flow during a dive

Lillie

Vogl

Raverty³

et al. 2018

Journal of Experimental Biology

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A sphincter on the inferior vena cava can protect the heart of a diving mammal from overload when elevated abdominal pressures increase venous return, yet sphincters are reported incompetent or absent in some cetacean species. We previously hypothesized that abdominal pressures are elevated and pulsatile in fluking cetaceans, and that collagen is deposited on the diaphragm according to pressure levels to resist deformation. Here, we tested the hypothesis that cetaceans generating high abdominal pressures need a more robust sphincter than those generating low pressures. We examined diaphragm morphology in seven cetacean and five pinniped species. All odontocetes had morphologically similar sphincters despite large differences in collagen content, and mysticetes had muscle that could modulate caval flow. These findings do not support the hypothesis that sphincter structure correlates with abdominal pressures. To understand why a sphincter is needed, we simulated the impact of oscillating abdominal pressures on caval flow. Under low abdominal pressures, simulated flow oscillated with each downstroke. Under elevated pressures, a vascular waterfall formed, greatly smoothing flow. We hypothesize that cetaceans maintain high abdominal pressures to moderate venous return and protect the heart while fluking, and use their sphincters only during low-fluking periods when abdominal pressures are low. We suggest that pinnipeds, which do not fluke, maintain low abdominal pressures. Simulations also showed that retrograde oscillations could be transmitted upstream from the cetacean abdomen and into the extradural veins, with potentially adverse repercussions for the cerebral circulation. We propose that locomotion-generated pressures have influenced multiple aspects of the cetacean vascular system.

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The Caval Sphincter in Phoca vitulina L.

Cited by 7 publications

References 0 publications

Functional morphology of the vascular plexuses associated with the cetacean uterus

Functional morphology of the vascular plexuses associated with the cetacean uterus

Venous structures associated with thermoregulation of phocid seal reproductive organs

The caval sphincter in cetaceans and its predicted role in controlling venous flow during a dive

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