James T N, Kawamura K, Meijler F L, Yamamoto S, Terasaki F, Hayashi T
Department of Medicine, University of Texas Medical Branch, Galveston 77555-0129, USA.
Anat Rec. 1995 Jul;242(3):355-73. doi: 10.1002/ar.1092420309.
Atrioventricular (AV) conduction time in large whales is only slightly greater than in smaller mammals even though their hearts are enormously larger. Little is known of the detailed histology or cytology of the conduction system of large whales. Such knowledge could be useful in defining the nature of cardiac rhythm and conduction of the whale as well as smaller mammals including humans.
We studied hearts from seven sperm whales. After fixation in formaldehyde and later dissection, specimens were prepared for histological examination.
Cell size, histological organization, and innervation of the sperm whale's sinus node, AV node, and His bundle are similar to most mammalian hearts, except the sinus node is substantially larger. There is no central fibrous body between the atrial and ventricular septa, and the whale has no os cordis. Only the upper quarter of the interventricular septum is fully formed; below that there is only a thin layer of fatty connective tissue between the two ventricles.
Given our morphological findings, we believe that the whale's comparatively short AV conduction time may be best explained by the sinus node and AV node functioning as coupled relaxation oscillators. Absence of an os cordis or central fibrous body or strong attachment between the two ventricles may pose both electrophysiological and hemodynamic hazards when the whale is no longer in its normally buoyant aquatic environment.
大型鲸鱼的房室传导时间仅略长于小型哺乳动物，尽管它们的心脏要大得多。关于大型鲸鱼传导系统的详细组织学或细胞学知之甚少。这些知识有助于明确鲸鱼以及包括人类在内的小型哺乳动物的心律和传导特性。
我们研究了7头抹香鲸的心脏。在甲醛固定并随后解剖后，制备标本用于组织学检查。
抹香鲸的窦房结、房室结和希氏束的细胞大小、组织学结构和神经支配与大多数哺乳动物的心脏相似，只是窦房结明显更大。心房和心室间隔之间没有中央纤维体，鲸鱼也没有心骨。只有室间隔的上四分之一完全形成；在其下方，两个心室之间只有一层薄薄的脂肪结缔组织。
根据我们的形态学发现，我们认为鲸鱼相对较短的房室传导时间可能最好用窦房结和房室结作为耦合弛豫振荡器来解释。当鲸鱼不再处于正常漂浮的水生环境中时，没有心骨或中央纤维体或两个心室之间的牢固连接可能会带来电生理和血液动力学风险。
