Anatomy of a Muscle Cell

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Anatomy of Muscle Cells

There are three types of muscle tissue in the human body. These muscle tissues are skeletal muscles, smooth muscles and cardiac muscles. Each of these muscle tissues has it very own anatomical makeup, which vary from muscle to muscle. The muscle cells in a muscle are referred to as muscle fibers, these fibers are skeletal muscle fibers, smooth muscle fibers and cardiac muscle fibers. The anatomy of a skeletal muscle fiber is formed during embryonic development. Skeletal muscle fibers arise from a hundred or more small mesodermal cells called myoblasts. The mature skeletal muscle fiber has a hundred or more nuclei. Once fusion occurs the skeletal muscle fiber will lose the ability to undergo cell division. This means that the number of muscle fibers is set before birth and most of these fibers will last a lifetime. The muscle growth that occurs after birth is a result of the enlargement of these existing muscle fibers. The mature muscle fibers have a few myoblasts, which remain as satellite cells. These myoblasts retain the capacity to join with one another or with damaged muscle fibers in order to regenerate these muscle fibers.

John Centore2
Dr. Jain
Anatomy & Physiology

The many nuclei of skeletal muscle fiber are located underneath the sarcolemma, which is the fiber's plasma membrane. Thousands of invaginations of the sarcolemma, which are called T Tubules, Tunnel from the surface to the center of the muscle fiber. These T Tubules are open to the outside of the fiber and are filled with extra-cellular fluid. Muscle action potentials propagate along the sarcolemma and through the T tubules and quickly spread through the muscle fiber. This process ensures that all parts of the muscle fiber become excited by an action potential virtually simultaneously. The sarcoplasm is located inside the sarcolemma. Sarcoplasm is the cytoplasm of a muscle fiber, it contains a good amount of glycogen,...
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