Icardo J M, Colvee E
Department of Anatomy and Cell Biology, University of Cantabria, Santander, Spain.
Anat Rec. 1998 Dec;252(4):509-18. doi: 10.1002/(SICI)1097-0185(199812)252:4<509::AID-AR2>3.0.CO;2-O.
The papillary muscles (PM) of the heart have been the subject of numerous structural and functional studies. However, despite the importance of the collagenous compartment of the heart in the mechanical and electrical properties of the myocardium, little information is available on the structural organization of collagen within the PM. We study here the structural organization of collagen within the mitral papillary muscles (PM) of the human heart. Fragments of human mitral PM from normal and hypertensive subjects were macerated in NaOH to eliminate the cellular components. Macerated and nonmacerated samples were then studied with the scanning electron microscope (SEM). SEM shows that cardiac myocytes and endomysial capillaries are ensheathed in a layer of collagenous tissue. The myocyte sheath wall is formed by thin collagen fibers oriented at right angles to the main cell axis. These sheaths are open structures, collagen fibers continuing into adjacent sheaths at the points of lateral communications. Thick perimysial septa do not divide the PM tissue into separate compartments. Hypertensive hearts show perivascular and interstitial fibrosis. In addition, the lumen of the coronary vessels is reduced or obliterated, and large areas of the myocardium are substituted by densely packed collagen. Endomysial sheaths constitute a continuous collagenous layer that replicates the myocyte network. The endomysium should play a complex role in myocardial mechanics, assuring the equal distribution of force during the cardiac cycle. The absence of insulating boundaries should facilitate lateral propagation of excitation. Fibrosis in hypertensive hearts appears to be both reactive and reparative. The increase in the amount of collagen should greatly impair contractile capabilities and electrical conductance, severely compromise heart function, and contribute to development of heart failure.
心脏的乳头肌（PM）一直是众多结构和功能研究的对象。然而，尽管心脏的胶原成分在心肌的机械和电学特性中具有重要意义，但关于乳头肌内胶原的结构组织却知之甚少。我们在此研究人类心脏二尖瓣乳头肌（PM）内胶原的结构组织。将来自正常和高血压受试者的人类二尖瓣PM片段在NaOH中浸软以去除细胞成分。然后用扫描电子显微镜（SEM）研究浸软和未浸软的样本。SEM显示心肌细胞和肌内膜毛细血管被一层胶原组织包裹。心肌细胞鞘壁由与细胞主轴线成直角排列的细胶原纤维形成。这些鞘是开放结构，胶原纤维在横向连通点处延续到相邻的鞘中。粗大的肌束膜间隔并未将PM组织分隔成独立的隔室。高血压心脏表现出血管周围和间质纤维化。此外，冠状血管腔变窄或闭塞，大片心肌被密集堆积的胶原所取代。肌内膜鞘构成一个连续的胶原层，复制了心肌细胞网络。肌内膜在心肌力学中应发挥复杂作用，确保在心动周期中力的均匀分布。缺乏绝缘边界应有助于兴奋的横向传播。高血压心脏中的纤维化似乎兼具反应性和修复性。胶原量的增加应会极大地损害收缩能力和电传导，严重损害心脏功能，并促成心力衰竭的发展。
