CARDIAC MUSCLE

Cardiac Muscle (LM, H&E) [#16, 28]- Cardic muscle, which is an involuntary, striated muscle, is peculiar to the heart and to the roots of large veins entering the heart (in particular, pulmonary veins). The cardiac muscle is distinguished by the presence of striations, intercalated disks, branching, and single nuclei which are centrally located within the cell.

This type of muscle tissue is found in the walls of the heart as sheets of muscle fibers arranged spirally or as loops in the middle layer of the wall of the heart (i.e. the myocardium). Therefore, a section in this layer will cut the muscle fibers in various planes and thus fibers in cross, oblique and longitudinal sections will be seen. Note the central location of the nuclei within the cells and the fine transverse striations and compare these with the nuclei and striations in the skeletal muscle fibers. Also note that the individual muscle fibers are smaller in diameter than skeletal muscle fibers. They branch and anastomose with each other but they do not form a continous protoplasmic mass or "syncytium" because the cells (fibers) are separated at the intercalated disks. The intercalated discs can be seen as slightly darker staining lines parallel to the transverse striations.

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	Slide Text CARDIAC MUSCLE Cardiac Muscle (LM, H&E) [#16, 28]- Cardic muscle, which is an involuntary, striated muscle, is peculiar to the heart and to the roots of large veins entering the heart (in particular, pulmonary veins). The cardiac muscle is distinguished by the presence of striations, intercalated disks, branching, and single nuclei which are centrally located within the cell. This type of muscle tissue is found in the walls of the heart as sheets of muscle fibers arranged spirally or as loops in the middle layer of the wall of the heart (i.e. the myocardium). Therefore, a section in this layer will cut the muscle fibers in various planes and thus fibers in cross, oblique and longitudinal sections will be seen. Note the central location of the nuclei within the cells and the fine transverse striations and compare these with the nuclei and striations in the skeletal muscle fibers. Also note that the individual muscle fibers are smaller in diameter than skeletal muscle fibers. They branch and anastomose with each other but they do not form a continous protoplasmic mass or "syncytium" because the cells (fibers) are separated at the intercalated disks. The intercalated discs can be seen as slightly darker staining lines parallel to the transverse striations.