Lymphatics of the cardiac chordae tendineae with particular consideration of their origin

We traced the origin of lymphatic capillaries of the chordae tendineae by serial ultrathin sections and electron microscopy of lymphatics identified first by light microscopy at the base of the chordae tendineae. Most of the lymphatics appear flattened in cross section, approximately 15 to 20 microns and 3 to 5 microns in greater and lesser diameters, respectively. Spiny (thorn-like) branchlets (about 10 microns in length) randomly projected from the sides of straight lymphatic capillaries and each was composed of a single endothelial cell with marginal zones in apposition to one another. The extreme end of a straight lymphatic capillary terminated blindly and consisted of a single endothelial cell with an ultrastructural appearance that resembled that of the spiny branchlets.