FIGURE 5.

Electron micrographs of rabbit ventricular myocytes. (A) The cross-sectional image shows t-tubules (t) and their relation to z-disks (z) and myofilaments (myo). The image indicates that t-tubules invaginate the outer sarcolemma and are closely associated to z-disks. (B) The freeze fracture shows two t-tubules (t) connected by an anastomosis (a). Furthermore, the freeze fracture gives indications for constrictions (c) of the t-tubules. (C) A cross-sectional cut through three t-tubules is displayed in relation to z-disks, myofilaments, and mitochondria (mito). The cut through t-tubules indicates noncircular cross sections.