Scanning electron microscopical study of human mitral valve chordae tendineae.

Scanning electron microscopy was used to examine the surface and internal structure of adult human mitral valve chordae tendineae. The endocardial cell surface of the tissue was found to be relatively smooth and even. Just beneath the endocardial surface, widely spaced collagen fibers were found. These were observed to be aligned at an angle to the chordal long axis and to wrap themselves around the central collagen core. The chordal core consisted of relatively straight collagen fibers that were arranged with their axis parallel to the long axis of the chordae. At the microstructural level, these collagen fibers were observed to consist of a network of collagen fibrils. This architectural arrangement is an advantageous feature for a tissue that is under constant dynamic stress. The scanning observations were confirmed by transmission electron microscopy.