On the direction and velocity of blood flow in the extradural intravertebral vein of harp seals (Phoca groenlandica) during simulated diving

Ronald et al. (1977 ) suggested that blood flow in the caudal/lumbar sections of the extradural intravertebral vein (EIV) of seals changes direction from running towards the head before diving, to the opposite during diving. The possible advantage would be that the oxygen‐depleted venous effluent fr...

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Bibliographic Details
Published in:Acta physiologica Scandinavica 2000-02, Vol.168 (2), p.271-276
Main Authors: NORDGARDEN, U, FOLKOW, L. P, WALLOE, L, BLIX, A. S
Format: Article
Language:English
Subjects:
anatomy
Animals
Biological and medical sciences
blood distribution
Blood Flow Velocity
Diving - physiology
doppler ultrasound flowmetry
extradural intravertebral vein
Female
Fundamental and applied biological sciences. Psychology
Hemodynamics. Rheology
Male
Regional Blood Flow
Rheology
Seals, Earless - physiology
Space life sciences
Spinal Canal - blood supply
Veins - physiology
Vertebrates: cardiovascular system
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Summary:Ronald et al. (1977 ) suggested that blood flow in the caudal/lumbar sections of the extradural intravertebral vein (EIV) of seals changes direction from running towards the head before diving, to the opposite during diving. The possible advantage would be that the oxygen‐depleted venous effluent from the brain is routed via the EIV to the posterior parts of the hepatic sinuses and the inferior caval vein and, hence, is prevented from mixing with the more oxygen‐rich venous blood in their anterior parts. We have re‐examined this hypothesis by use of Doppler flowmetry. A catheter‐tip flow probe was introduced into the EIV of two similar‐sized juvenile harp seals, and flow direction and rate determined before, during and after simulated dives lasting for 5 min, at three positions (caudal, lumbar and thoracic) along the EIV. Regardless of probe position, blood was mainly flowing towards the head in 11 of 13 experiments prior to diving, in 8 of 13 experiments during diving and in 11 of 13 experiments during recovery after diving (and away from the head in the remaining experiments). Flow direction was most variable in the caudal position. Mean blood velocity in the EIV was substantially lower during diving (0.10 ± 0.22 cm s–1 (n=5) in thoracic position) than in the pre‐dive (3.98 ± 3.32 cm s–1 [n=5]) and post‐dive (5.75 ± 4.07 cm s–1 [n=5]) situations. Thus, the direction and rate of flow in the EIV was variable, particularly during diving, as is to be expected in a system of anastomosing, valveless veins. We conclude that the hypothesis of Ronald et al. (1977 ) most likely is false.
ISSN:0001-6772
1365-201X
DOI:10.1046/j.1365-201x.2000.00652.x