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The sarcolemma (sarco (from sarx) from Greek; flesh, and lemma from Greek; sheath), also called the myolemma, is the cell membrane surrounding a skeletal muscle fibre or a cardiomyocyte. [ 1 ] [ 2 ] It consists of a lipid bilayer and a thin outer coat of polysaccharide material ( glycocalyx ) that contacts the basement membrane .
The cell membrane of a cardiac muscle cell has several specialized regions, which may include the intercalated disc, and transverse tubules. The cell membrane is covered by a lamina coat which is approximately 50 nm wide. The laminar coat is separable into two layers; the lamina densa and lamina lucida.
A group of muscle stem cells known as myosatellite cells, also satellite cells are found between the basement membrane and the sarcolemma of muscle fibers. These cells are normally quiescent but can be activated by exercise or pathology to provide additional myonuclei for muscle growth or repair.
It overlies the muscle fiber's cell membrane: the sarcolemma. Endomysium is the deepest and smallest component of muscle connective tissue. This thin layer helps provide an appropriate chemical environment for the exchange of calcium, sodium, and potassium, which is essential for the excitation and subsequent contraction of a muscle fiber.
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.
The sarcoplasmic reticulum is a network of the tubules that extend throughout muscle cells, wrapping around (but not in direct contact with) the myofibrils (contractile units of the cell). Cardiac and skeletal muscle cells contain structures called transverse tubules (T-tubules), which are extensions of the cell membrane that travel into the ...
The cell membrane has different lipid and protein compositions in distinct types of cells and may have therefore specific names for certain cell types. Sarcolemma in muscle cells: Sarcolemma is the name given to the cell membrane of muscle cells. [46] Although the sarcolemma is similar to other cell membranes, it has other functions that set it ...
A classic example of a syncytium is the formation of skeletal muscle.Large skeletal muscle fibers form by the fusion of thousands of individual muscle cells. The multinucleated arrangement is important in pathologic states such as myopathy, where focal necrosis (death) of a portion of a skeletal muscle fiber does not result in necrosis of the adjacent sections of that same skeletal muscle ...