Icardo J M, Colvee E
Departamento de Anatomía y Bilogía Celular, Facultad de Medicina, Universidad de Cantabria, Santander, Spain.
Anat Rec. 1995 Nov;243(3):367-75. doi: 10.1002/ar.1092430311.
The leaflet tissue of the mouse atrioventricular (AV) valves contains a system of wavy collagen bundles that organize like tendons, orientate along lines of tension, and constitute an essential component of the valve tissue. The organization of these bundles is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Further insights into this kind of organization are needed to gain a complete understanding of the functional anatomy of the mouse AV valves.
The endocardial covering of the mouse AV valves (from 21 days to 1 year of age) was eliminated by the sonication or the maceration method. This allowed us to study in situ the organization of the collagenous valve skeleton, as well as the structure of the myotendinous junction.
The leaflets of the two AV valves are formed by a fibrous layer (on the ventricular side) and a spongy layer (on the atrial side). The fibrosa is formed by undulating collagen bundles that organize and orientate differently on the right and left sides. The spongiosa is formed, on both sides, by a loose network of thin collagen fibers with no apparent orientation. Myocardial cells in the papillary muscles of the tricuspid valve are elongated and show cone-shaped tips. Collagen fibers attach to the myocyte surface. Collagen struts and thin septa can also be recognized. On the other hand, the collagenous components of the mitral leaflets attach tangentially to the mitral papillary muscles. On the two sides, the myocytes appear to be ensheathed in a layer of collagenous tissue. The sheaths are formed by circularly arranged fibers and appear to be tightly interconnected.
The differences in the collagenous organization between the two AV valves reflect differences in the gross anatomy of the valves. The attachment of collagen to the papillary myocytes in the tricuspid valve resembles that of a typical myotendinous junction. However, the collagen-muscle junction in the mitral valve is more similar to the structure of a pennate muscle. The collagen matrix of the heart has been divided into endomysial, perimysial, and epimysial components. The presence of sheaths housing individual myocytes and capillaries, struts, and thin septa, corresponds to the endomysium. The absence of perimysial septa, which aggregate myocytes into groups, is striking, but this may just be a species difference. The appropriateness of the term epimysium, as applied to the heart, is discussed.
小鼠房室（AV）瓣的瓣叶组织包含一个波浪状胶原束系统，这些胶原束像肌腱一样组织起来，沿张力线排列，是瓣膜组织的重要组成部分。这两个房室瓣中这些束的组织方式不同，反映了整个瓣膜复合体解剖结构的差异。需要对这种组织方式有更深入的了解，才能全面理解小鼠房室瓣的功能解剖结构。
通过超声处理或浸软法去除小鼠房室瓣（21天至1岁）的心内膜覆盖物。这使我们能够在原位研究胶原瓣膜骨架的组织以及肌腱连接的结构。
两个房室瓣的瓣叶由纤维层（心室侧）和海绵层（心房侧）组成。纤维层由起伏的胶原束形成，左右两侧的排列和方向不同。海绵层两侧均由薄胶原纤维的疏松网络形成，无明显方向。三尖瓣乳头肌中的心肌细胞细长，尖端呈锥形。胶原纤维附着于心肌细胞表面。还可识别出胶原支柱和薄间隔。另一方面，二尖瓣瓣叶的胶原成分与二尖瓣乳头肌呈切向附着。两侧的心肌细胞似乎被一层胶原组织包裹。这些鞘由环形排列的纤维形成，似乎紧密相连。
两个房室瓣胶原组织的差异反映了瓣膜大体解剖结构的差异。三尖瓣中胶原与乳头肌心肌细胞的附着类似于典型的肌腱连接。然而，二尖瓣中的胶原 - 肌肉连接更类似于羽状肌的结构。心脏的胶原基质已被分为肌内膜、肌束膜和肌外膜成分。存在包裹单个心肌细胞和毛细血管的鞘、支柱和薄间隔，对应于肌内膜。明显缺乏将心肌细胞聚集在一起的肌束膜间隔，但这可能只是物种差异。讨论了将肌外膜一词应用于心脏的恰当性。
