Sans-Coma V, Gallego A, Muñoz-Chápuli R, De Andrés A V, Durán A C, Fernández B
Department of Animal Biology, Faculty of Science, University of Málaga, Spain.
Anat Rec. 1995 Apr;241(4):496-504. doi: 10.1002/ar.1092410407.
Knowledge of the structural arrangement of the cardiac conal valves in Elasmobranchs is scarce. The present study was designed to assess the anatomical and histological features of the conal valves of the dogfish as a starting point for further investigation of the mechanical properties of these valves.
The sample examined consisted of 31 adult dogfishes. The study was carried out using scanning electron microscopy and histological techniques for light microscopy.
In the dogfish, the conus arteriosus contains two transverse rows of valves. The anterior row lies at the level of the conus-ventral aorta junction and is composed of three valves of similar size. The posterior row is near the conus-ventricular junction and consists of four valves, one of them very reduced in size. Each valve shows two components, namely, the leaflet and its supporting structure, the sinus. In the anterior valves, the length of the leaflets between their lateral attachments to the sinus wall is remarkably longer than the straight-line distance between the points of attachment. This allows each leaflet to close against the other two leaflets of the same row, even when the conus is relaxed. The leaflets of the posterior valves are anchored to the conus wall by means of tendinous cords and cannot practically bridge the lumen of the relaxed conus. Each leaflet has a stout central body in which the connective tissue is stratified in three layers: outer fibrosa, spongiosa, and inner fibrosa. The lateral parts of the leaflet mainly consist of a single fibrous layer that bifurcates into the outer and inner fibrosa layers of the central body. The sinus walls of the posterior valves are entirely made up of conal tissue, whereas those of the anterior valves incorporate an aortic component.
The present findings suggest that the inner fibrosa and the fibrous lateral portions of the leaflets mainly bear the stress of pressure generated by blood backflow. The stretching of the leaflets in the radial direction may basically depend on the spongiosa, whereas the outer fibrosa determines the radial stiffness of the leaflets.
关于板鳃亚纲动物心脏圆锥瓣膜结构排列的知识匮乏。本研究旨在评估角鲨圆锥瓣膜的解剖学和组织学特征，作为进一步研究这些瓣膜力学特性的起点。
所检查的样本包括31条成年角鲨。研究采用扫描电子显微镜和光学显微镜组织学技术进行。
在角鲨中，动脉圆锥包含两排横向瓣膜。前排位于圆锥 - 腹主动脉交界处水平，由三个大小相似的瓣膜组成。后排靠近圆锥 - 心室交界处，由四个瓣膜组成，其中一个瓣膜尺寸非常小。每个瓣膜有两个组成部分，即瓣叶及其支撑结构窦。在前瓣膜中，瓣叶在其与窦壁的侧向附着点之间的长度明显长于附着点之间的直线距离。这使得每个瓣叶即使在圆锥松弛时也能与同一排的其他两个瓣叶闭合。后瓣膜的瓣叶通过腱索固定在圆锥壁上，实际上无法在松弛的圆锥腔内形成桥接。每个瓣叶有一个粗壮的中央体，其中结缔组织分为三层：外层纤维层、海绵层和内层纤维层。瓣叶的侧向部分主要由单层纤维层组成，该纤维层分叉形成中央体的外层和内层纤维层。后瓣膜的窦壁完全由圆锥组织构成，而前瓣膜的窦壁包含主动脉成分。
目前的研究结果表明，瓣叶的内层纤维层和纤维侧向部分主要承受血液回流产生的压力应力。瓣叶在径向方向上的伸展可能主要取决于海绵层，而外层纤维层决定瓣叶的径向刚度。
