ISSN:
1432-0878
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Electron micrographs of the conducting system of the sheep heart show it to be strictly cellular in nature. All protoplasmic components are restricted to areas defined by the individual plasma membranes of the cells. The individual cells are surrounded by a common interspace and groups of cells are separated from neighboring connective tissue by a common, longitudinal basement membrane. The extracytoplasmic interspace shows occasional enlargements, probably corresponding to the “intracytoplasmic vacuoles” visualized in the light microscope. The apposing plasma membranes, along which ephaptic thickenings may occur, and their interspace form the intercalated discs of the system. Myofibrils are few and are situated preferentially immediately beneath the plasma membrane. Chains of myofibrils, interrupted at the intercalated discs, appear to course through the whole tissue. In some myofibrils the pattern of long periods may be interrupted by a small-period pattern for several sarcomeres. The cytoplasmic matrix consists mainly of fine filaments of unknown composition. The relatively scarce mitochondria are found near the nucleus, myofibrils and cell surface. The endoplasmic reticulum is poorly developed and its arrangement is a comparatively loose one. The above results and their physiologic consequences are discussed, particularly with regard to the core conduction theory in conducting tissue.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00398655
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