Muscle Tissue Li-Dongmei

Overview of muscle tissue The myocytes is also called muscle fibers. The cytoplasm is called sarcoplasm, and the smooth endoplasmic reticulum is called sarcoplasmic reticulum. The sarcolemma is the cell membrane.

Two principal types: Type Striated muscle Smooth muscle Skeletal muscle Cardiac muscle contraction voluntary involuntary Location Limbs body wall Heart Viscera

Skeletal muscle Long,cylindrical fibers,multinucleated syncytium. The nuclei are located in the cytoplasm beneath the sarcolemma. Muscle fibers show transverse-striation (cross-striation).

Skeletal muscle-myofibrils The structural and functional subunit of the muscle fiber. They contribute to the formation of transverse-striation. They have A bands(darker bands), H bands, M lines, I bands(lighter bands) and Z lines.

Skeletal muscle-sarcomere The sarcomere is the segment of the myofibril between two adjacent Z lines. It is the basic contractive unit of striated muscle.

Skeletal muscle-connective tissue The skeletal muscle fibers are held by connective tissue named as: endomysium, perimysium and epimysium.

Skeletal muscle-myofilaments Two types of myofilaments are associated with cell contraction. They are thin filaments and thick filaments.

Skeletal muscle-contraction When a muscle contracts, each sarcomere shortens and becomes thicker, but the myofilaments remain the same length.

Skeletal muscle -sarcoplasmic reticulum A series of networks around the myofibrils. At the junction between A and I bands, they forms the terminal cisterna.

Skeletal muscle -transverse tubule system It consists of numerous tubular invaginations of the plasma membrane, each one is called a T tubule. They located between adjacent terminal cisternae. The complex of T tubule and the two adjacent terminal cisternae is called a triad.

Similarities between cardiac muscle and skeletal muscle Made up of elongated fibers. Myofibrils show transverse- striations. Myofibrils also made up of thin and thick filament.

Differences between cardiac muscle and skeletal muscle The fibers branch and anastomose with other fibers to form a network. Each cardiac muscle cell possesses only one or two centrally located nucleus. A unique and distinguishing characteristic is the presence of intercalated disks. Intercalated disks represent junctional complexs.

Differences between cardiac muscle and skeletal muscle Myofibrils and striations are not distinct. The sarcoplasmic reticulum is less prominent. The T tubule lie oppsite the z-lines. It possesses diads composed of one T tubule and one terminal cisterna.

Smooth muscle Smooth muscle cells are fusiform. Each cell has a single nucleus located in the center of the broadest part of the cell.

Smooth muscle In smooth muscle cells, bundles of myofilaments crisscross through the cell, forming a latticelike work. The cytoskeleton contains cytoplasmic densities or dense bodies,intermediate filaments. Smooth muscle cells have a membrane system of sarcolemmal invaginations, vesicles, and SER but lack a T system.

Summary The structure of skeletal muscle. The structure of cardiac muscle. The structure of smooth muscle.