. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Fig. 292. Evolution of the heart, a, elasmobranchs; b, teleosts; c, amphj bians; d, lower reptiles; e, alligators; f, birds and mammals; a, atrium or auricle; v, ventricle; , aorta; b, bulbus arteriosus; c, conus; , duct of Cuvier; h, hepatic veins; ,, pulmonary artery; , post-caval vein; , pulmonary vein; s, sinus venosus; t, truncus arteriosus. (After Kingsley.) aeration must make the grand tour of the body and become again non- aerated
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Fig. 292. Evolution of the heart, a, elasmobranchs; b, teleosts; c, amphj bians; d, lower reptiles; e, alligators; f, birds and mammals; a, atrium or auricle; v, ventricle; , aorta; b, bulbus arteriosus; c, conus; , duct of Cuvier; h, hepatic veins; ,, pulmonary artery; , post-caval vein; , pulmonary vein; s, sinus venosus; t, truncus arteriosus. (After Kingsley.) aeration must make the grand tour of the body and become again non- aerated before it is returned to its starting point in the heart. Beginning posteriorly the four chambers in the heart of elasmobranch fishes are the sinus venosus, atrium, ventricle, and conus arteriosus (Fig. 291b). The first two belong to the re- ceiving region of the heart and are reservoirs with elastic rather than thick muscular walls, while the ventricle is thick-walled and muscular, as befits the forwarding pump of the blood. The conus has a muscular wall of moderate thickness, which by its elas- ticity aids in regulating the back pres- sure of the blood as it is forced through the ventral aorta into the nearby capil- laries of the gills. In elasmobranchs the single atrium receives the blood that has been poured into the sinus venosus from the ducts of Cuvier and the hepatic veins (Fig. 292). A row of cup-like valves, with their concavities in front, guard the atrio-ventricular opening permitting the blood to go into the ventricle but filling with blood to block the opening when the ventricle contracts to force the blood through the conus (Fig. 293). Several rows of semilunai. Ventral Aorta --Afferent Branchial Artery 3 — Conus Arteriosus Atrio-Ventricular Opening Sinu-Atrial Cpenina Fig. 293. Heart and ventral aorta of Squalus acanthias, from the dorsal side. with the atrium cut open. (After Rose.). Please note that these images are extracted from scanned page images that ma
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Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
