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A muscle cell, also known as a myocyte, is a mature contractile cell in the muscle of an animal. [1] In humans and other vertebrates there are three types: skeletal, smooth, and cardiac (cardiomyocytes). [2]
Cardiac muscle histology 400x. Myocytes are incredibly specialized cells with only a select number of different organelle types. A myocyte is composed of multiple myofibrils, which contain the “contractile units” of the muscle known as a sarcomere. [3] These sarcomeres are arranged in adjacent formations along the myofibrils.
Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart .
Basic cardiac action potential. Unlike the action potential in skeletal muscle cells, the cardiac action potential is not initiated by nervous activity.Instead, it arises from a group of specialized cells known as pacemaker cells, that have automatic action potential generation capability.
Intercalated discs or lines of Eberth are microscopic identifying features of cardiac muscle. Cardiac muscle consists of individual heart muscle cells (cardiomyocytes) connected by intercalated discs to work as a single functional syncytium. By contrast, skeletal muscle consists of multinucleated muscle
Cardiomyocytes, are considerably shorter and have smaller diameters than skeletal myocytes. Cardiac muscle (like skeletal muscle) is characterized by striations – the stripes of dark and light bands resulting from the organised arrangement of myofilaments and myofibrils in the sarcomere along the length of the cell.
T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.
Finally, the muscle fibers that form later arise from satellite cells. [3] Two genes significant in muscle fusion are Mef2 and the twist transcription factor. Studies have shown knockouts for Mef2C in mice lead to muscle defects in cardiac and smooth muscle development, particularly in fusion. [13] The twist gene plays a role in muscle ...