Respiratory, cardiovascular and abdominal anatomy of the ringed seal (Phoca hispida) [electronic resource] / Hrvoje Smodlaka.

Thesis (Ph. D.) -- University of Tennessee, Knoxville, 2004.

Document formatted into pages (xii, 155 p. : ill. (chiefly col)).

Title from title page screen (viewed on Sept. 30, 2004).

This study investigated the anatomy the ringed seal (Phoca hispida) cardiovascular system (heart and large vessels) and lower respiratory tract (lung), as well as the topographic anatomy of the seal abdomen. The ringed seal heart is dorsoventrally flattened, with each ventricle residing on its respective side within the thoracic cage. The heart lies horizontal, parallel to the sternum. The right ventricle is long, spacious and thin walled. The right coronary artery continues as the subsinuosal interventricular branch, making it different from domestic carnivores. The aortic bulb is a large structure in comparison to the equivalent structure in terrestrial mammals, which is hardly noticeable. It lies in contact with the cranioventral aspect of the thoracic cavity. The aortic arch gives rise to three major blood vessels; brachiocephalic trunk, left common carotid and left subclavian artery. The paired caudal vena cavae continue the pelvic venous plexus as paired vessels through the caudal abdominal cavity. At the level of the third lumbar vertebral body the two separate limbs converge into a single vena cava. Soon after this junction as the hepatic veins join the vena cava, they expand into a large hepatic sinus. As the caudal vena cava passes through the diaphragm, muscle fibers of the diaphragm form a caval sphincter. The azygos veins are paired and join into a common trunk before emptying into the cranial vena cava as it enters the right atrium. Intercostal arteries perforate the right azygos vein. There are also communications between left and right azygos veins via short anastomosing branches. The pericardial venous plexus is present in the mediastinal pleura as a loop encompassing the apex of the heart. It is comprised of convoluted veins that eventually drain into the caudal vena cava as a single trunk. Pulmonary arteries are paired vessels that divide into caudal and cranial branches at the level of the principal bronchi. Three common pulmonary veins drain the lung lobes into the left atrium. The lungs are subdivided into seven lung lobes. The right lung is divided into cranial, middle, caudal and accessory lung lobes. The left lung is divided into cranial, middle and caudal lobes. The pulmonary trunk upon reaching the atrial face of the heart divides into the left and right pulmonary arteries that lie adjacent to and follow the dichotomy of the bronchial tree. Three common pulmonary veins are formed by merging of the lobar veins. The common left and right veins drain their respective cranial and middle lobes while the caudal common vein drains both left and right caudal lobes and the accessory lobe. The ringed seal has three major tracheobronchial lymph nodes.