Functional anatomy of the coronary system of the harbour porpoise, Phocoena phocoena (L.)

• Published in: Canadian Journal of Zoology
• Main Authors: Halina, W. G., Gaskin, D. E.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1978
• Subjects: Harbour porpoise; Phocoena phocoena
• Online Access: http://dx.doi.org/10.1139/z78-227; http://www.nrcresearchpress.com/doi/pdf/10.1139/z78-227

The heart of the harbour porpoise, Phocoena phocoena (L.), is a dorsoventrally flattened, cone-shaped organ which is large relative to the size of the animal. The cardiac fibres also have a large diameter compared with those of terrestrial mammals and may be capable of exerting a greater contractile force. Atrial and ventricular fibroelastosis are present, indicating that the chambers could distend, thereby permitting engorgement during a dive. The gross coronary vascular pattern is similar to that found in terrestrial mammals except that the right coronary artery supplies the larger area of tissue in most specimens. The major coronary arteries and veins are elastic, not muscular, and are therefore distensible. When the diastole of bradycardia is prolonged during a dive, these vessels may be capable of retaining an increased volume of blood, regulating its distribution, and storing the energy necessary for its later distribution. Extensive subepicardial venous plexi, also containing much elastic tissue, can easily receive myocardial blood and pool it, relieving the pressure on the microcirculation and thereby reducing coronary vascular resistance while blood flow is maintained during a dive. These mechanisms could help extend diving time.