Muscle Tissue Li dongmei

Muscle function contraction for locomotion and skeletal movement contraction for propulsion contraction for pressure regulation

Overview of muscle tissue Composition: muscle cells + connective 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.

Classification

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

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

Endomysium perimysium epimysium.

Skeletal muscle Long, cylindrical fibers, multinucleated syncytium. The nuclei are located in the cytoplasm beneath the sarcolemma.

Skeletal muscle-myofibrils The structural and functional subunit of the muscle fiber. They contribute to the formation of cross-striation. Cross-striations: composed of alternating dark (A) and light (I) bands.

Skeletal muscle-sarcomere The sarcomere is the segment of the myofibril between two adjacent Z lines. It is the basic contractile unit of striated muscle. It consists of 1/2 I band + A band + 1/2 I band.

Light band: I band Z line: I band is Intersected by a thin dark line Dark band： A band H band： a pale thin H-band bisects the A-band M line： a very fine dark stripe is present in the middle of the H-band.

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. ---Network of smooth endoplasmic reticulum At the junction between A and I bands, they fused to form 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. Responsible for rapid conduction of impulses

Skeletal muscle -transverse tubule system The complex of T tubule and the two adjacent terminal cisternae is called a triad.

Cardiac muscle The cardiac muscle cell present short rod with branch, which links with each other. There is only one nucleus in the centre of the cardiac muscle cell. The present of dark staining transverse or steplike lines at the interface between adjacent cardiac muscle cells are called intercalated disks. The cross-striation of cardiac muscle cells is less obvious than striated skeletal muscle.

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 centrally located nucleus. Myofibrils and striations are not distinct. The sarcoplasmic reticulum is less prominent.

Differences between cardiac muscle and skeletal muscle It possesses diads composed of one T tubule and one terminal cisterna. A unique and distinguishing characteristic is the presence of intercalated disks.

intercalated disks diads

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.

Exercise 3 for Histology 1.What do blood cells include? 2.The structure of sarcomere.