Читать книгу Clinical Guide to Fish Medicine - Группа авторов - Страница 48

The heart lies in a rigid pericardial chamber surrounded by a large volume of pericardial fluid. The pericardial lumen communicates with the coelomic cavity via a pericardiocoelomic canal, which is usually closed unless the pericardial fluid pressure exceeds that in the coelomic cavity. The fluid in the pericardial cavity is reported to be different from the plasma and coelomic fluid (Tota 1999; Shuttleworth 2012). The elasmobranch heart is sometimes considered four‐chambered although that is a misnomer as it is not equivalent to the mammalian model. The heart consists linearly of the sinus venosus, atrium, ventricle, and conus arteriosus (similar to the bulbus arteriosus of teleosts). The sinus venosus is thin‐walled and very compliant. The atrium is flaccid with a volume larger than the ventricle, the thickest of the myocardial tissues. The conus arteriosus is tubular and thick with prominent valvular structures. Detailed circulatory anatomy of elasmobranchs is available (Hoar et al. 1983; Muñoz‐Chápuli and Satchell 1999). There is often a synchrony noted between respiratory and cardiac beat, but this is inconsistent and has no obvious clinical consequence (Shuttleworth 2012). Electrocardiograms are similar to other vertebrates with the exception of a V‐wave (depolarization of the sinus venosus) prior to the PQRS (Shuttleworth 2012).

There is a secondary vascular system (SVS) in elasmobranchs that has different blood values than the primary system (Muñoz‐Chápuli and Satchell 1999; Mylniczenko et al. 2006).