Comparative volumes and vascular microanatomy of the intrahepatic venous system of the harbour porpoise, Phocoena phocoena (L.)

• Published in: Canadian Journal of Zoology
• Main Authors: Hilton, J. W., Gaskin, D. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1978
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; The Portal; Harbour porpoise; Phocoena phocoena
• Online Access: http://dx.doi.org/10.1139/z78-311; http://www.nrcresearchpress.com/doi/pdf/10.1139/z78-311

The intrahepatic venous systems of the harbour porpoise, Phocoena phocoena, were studied using single and double injection techniques. Large band-like formations of elastin fibres were found in the dilated terminal portions of the major hepatic veins and the adjacent section of the caudal vena cava but not in the equivalent major branches of the thicker walled portal veins. The hepatic venous system increases in volume disproportionately with increase in body length and liver weight; the portal system does not. No distal sphincter formations were found in the major hepatic veins, nor were sphincters or valves present in the portal system. The vena cava, however, is surrounded by a loop of diaphragmatic muscle or 'caval sling,' which may cause significant occlusion of the vena cava following inspiration. The distensible terminal portions of the major hepatic veins and the adjacent portion of the caudal vena cava could then function as a temporary blood reservoir or 'intrahepatic sinus.' While this would be a relatively inefficient mechanism for preventing ventricular engorgement, it might be sufficient for the needs of P. phocoena, which is a relatively poor diver.