Muscle Tissue

General Characteristics Muscle tissue is composed of muscle cells, with CT between them. Muscle tissue is composed of muscle cells, with CT between them. property of contractility. property of contractility. Muscle cells are often termed muscle fibers (myofibres) Muscle cells are often termed muscle fibers (myofibres)

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. 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 of muscle tissue  Functionally Voluntary Voluntary Involuntary Involuntary  Structurally Striated Striated Smooth (unstriated) Smooth (unstriated)

Two principal types: Type Type Striated muscle Striated muscle Smooth muscle Skelet al muscle Visceral striated muscle Cardiac muscle contraction volunt ary involunt ary Location Limbs body wall Soft tissue HeartViscera

Combining 2 types of Classification Combining 2 types of Classification 1.Skeletal Muscle (Striated voluntary) 2.Cardiac Muscle (Striated Involuntary) 3.Smooth Muscle (Unstriated Involuntary) Involuntary)

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

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

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

Skeletal muscle-connective tissue The skeletal muscle fibers are held by connective tissue named as: endomysium, perimysium and epimysium. 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. Two types of myofilaments are associated with cell contraction. They are thin filaments and thick filaments. They are thin filaments and thick filaments.

Myofibrils EM reveals that myofibrils consists of bundles of thread like elements termed myofilaments. EM reveals that myofibrils consists of bundles of thread like elements termed myofilaments. 2 types of myofilaments a)Thick filaments - Myosin filaments, 1.5um long & 10nm in diameter b) Thin filaments - Actin filaments (Actin, Tropomyosin & Troponin) 1um in length & 5nm in diameter

Skeletal muscle-contraction When a muscle contracts, each sarcomere shortens and becomes thicker, but the myofilaments remain the same length. 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. A series of networks around the myofibrils. At the junction between A and I bands, they forms the terminal cisterna. 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. It consists of numerous tubular invaginations of the plasma membrane, each one is called a T tubule. They located between adjacent terminal cisternae. They located between adjacent terminal cisternae. The complex of T tubule and the two adjacent terminal cisternae is called a triad. The complex of T tubule and the two adjacent terminal cisternae is called a triad.

Skeletal muscle-characters There are three types of skeletal muscle fibers: red fibers, white fibers and intermediate fibers. There are three types of skeletal muscle fibers: red fibers, white fibers and intermediate fibers.

2. Cardiac Muscle Involuntary striated muscle Involuntary striated muscle Cells are Short column in shape about 100um long & 15um in diameter. Cells are Short column in shape about 100um long & 15um in diameter. Cross-striated with A-I-Z-M & H bands are less distinct than skeletal muscle. Cross-striated with A-I-Z-M & H bands are less distinct than skeletal muscle. Intercalated discs Intercalated discs Contracts rhythmically Contracts rhythmically

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

Differences between cardiac muscle and skeletal muscle The fibers branch and anastomose with each other fibers to form a network. The fibers branch and anastomose with each other fibers to form a network. Each cardiac muscle cell possesses only one or two centrally located nucleus. Each cardiac muscle cell possesses only one or two centrally located nucleus. Myofibrils and striations are not distinct. Myofibrils and striations are not distinct. The sarcoplasmic reticulum is less prominent. The sarcoplasmic reticulum is less prominent.

Differences between cardiac muscle and skeletal muscle The T tubule lie at the level of the Z-line rather then at the A-I junction. The T tubule lie at the level of the Z-line rather then at the A-I junction. It possesses diads composed of one T tubule and one terminal cisterna. It possesses diads composed of one T tubule and one terminal cisterna. A unique and distinguishing characteristic is the presence of intercalated disks. A unique and distinguishing characteristic is the presence of intercalated disks. Intercalated disks represent junctional complexs. Intercalated disks represent junctional complexs.

3.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 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. 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. 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. Smooth muscle cells have a membrane system of sarcolemmal invaginations, vesicles, and SER but lack a T system.

4. Contraction Mechanism Sliding Filament Hypothesis During construction of skeletal muscle, A-band remained constant in length. Whilst the I-band & H-band both decreased. Both thick and thin filaments retained their original length during contractions.

Contraction Mechanism Sliding Filament Hypothesis Contraction results from an increase in amount of overlap between the thick and thin filaments. Free ends of actin filaments are inserted further into the A-band.

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

Homework Review the characteristics of muscle tissue. Review the characteristics of muscle tissue.