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However, cardiac muscle cells contain a diad, which is a linking of only one sarcoplasmic reticulum with its respective t-tubule. Another notable distinction between all muscle cells and cardiac muscle cells is the presence of intercalated discs. These tight connections between the cardiomyocytes allows for the accelerated sending of action ...
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.
In mammals, triads are typically located at the A-I junction; [1] that is, the junction between the A and I bands of the sarcomere, which is the smallest unit of a muscle fiber. Triads form the anatomical basis of excitation-contraction coupling , whereby a stimulus excites the muscle and causes it to contract.
The unusual microscopic anatomy of a muscle cell gave rise to its terminology. The cytoplasm in a muscle cell is termed the sarcoplasm; the smooth endoplasmic reticulum of a muscle cell is termed the sarcoplasmic reticulum; and the cell membrane in a muscle cell is termed the sarcolemma. [9] The sarcolemma receives and conducts stimuli.
Cardiac muscle cells of the right atrium can be seen to the left of the node, and fat tissue to the right. The cells of the SA node are spread out within a mesh of connective tissue, containing nerves, blood vessels, collagen and fat. Immediately surrounding the SA node cells are paranodal cells. [2]
Cardiac muscle cells generally only contain one nucleus, located in the central region. They contain many mitochondria and myoglobin. [5] Unlike skeletal muscle, cardiac muscle cells are unicellular. [4] These cells are connected to each other by intercalated disks, which contain gap junctions and desmosomes. [5]
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These satellite cells are the main source of most muscle cell formation postnatally, with embryonic myoblasts being responsible for prenatal muscle generation. A single satellite cell can proliferate and become a larger amount of muscle cells. [28] With the understanding that myosatellite cells are the progenitor of most skeletal muscle cells ...