Muscle Tissues Prof. Dr. ASHRAF M. Prof. of Histology

Muscle Tissues muscle cells called muscle fibers three types skeletal General characteristics muscle cells called muscle fibers contractile three types skeletal smooth cardiac Skeletal muscle attached to bones striated voluntary Smooth muscle walls of organs skin walls of blood vessels involuntary not striated Cardiac muscle heart wall involuntary striated intercalated discs

Types of Muscle Tissue Cardiac: only in the wall of the heart Skeletal Attach to and move skeleton 40% of body weight Fibers = multinucleate cells (embryonic cells fuse) Cells with obvious striations Contractions are voluntary Cardiac: only in the wall of the heart Cells are striated Contractions are involuntary (not voluntary) Smooth: walls of hollow organs Lack striations Contractions are involuntary (not voluntary)

Muscle Tissues Skeletal Muscle Smooth Muscle Cardiac Muscle

types 0f the muscles A- Skeletal, Striated and Voluntary. B- Cardiac, Striated and Involuntary. C- smooth non-striated &Involuntary

Connective Tissue Coverings epimysium perimysium fascicles endomysium muscle fascicles muscle fibers myofibrils thick and thin filaments

Type of skeletal muscle fibres Red muscle fibres White muscle fibres : Intermediate muscle fibres

Red muscle fibres irregular striations . abundant cytoplasm . rich in myoglobin , mitochondria . can contract for long time without fatigue

less myoglobin , mitochondria . quick , short contractions , White muscle fibres regular striations . less myoglobin , mitochondria . quick , short contractions , easily fatigued .

Intermediate muscle fibres : have intermediate characters between red and white fibres . *Skeletal muscle contain the 3 type but usually the white fibres predominate . * The diaphragm muscle of mastication contain red fibres only .

Structure of a Skeletal Muscle organ of the muscular system skeletal muscle tissue Skeletal muscle is also called voluntary muscle since it is under voluntary control.

Skeletal muscle fibers 1-The skeletal muscle is formed of elongated cells with two rounded ends and usually termed muscle fibers.

Skeletal muscle fibers The myofibrils appear as deep acidophilic dots within the fiber. -Each muscle fibers is about 1-40 mm in length and 10-100 um in diameter. -The muscle fiber is surrounded by delicate embrane known as Sarcolemma, which enclose the sarcoplasm of the fiber. -Each muscle fiber contain multiple, flat and peripheral nuclei.

Skeletal muscle fibers

Skeletal muscle fibers

The dark bands are Anisotropic ( A-bands ) . The light bands are Isotropic ( I – bands ) . The ( A ) band show a pale area in its center = H- zone divided by a dark line = M . The ( I ) band show a dark line in its center = Z- line .

Triad of tubular system It plays an important role in conducting the nerve impulse during muscle contraction . It includes : T-tubule : Formed by a invagination of thes arcolemma in to sarcoplasm , its cavity is continuous with the extensor . It extends transversely into sarcoplasm at the level between the A and I bands .

Triad of tubular system Sarcoplasmic reticulum : Modified longitudinal parts of sarcoplasmic reticulum and continuous slit . Each 2 sarcoplasmic tubules surround one t.v. T . tubule forming a triad . As the nerve impulse reaches the sarcolemma , it passes through T.tubules then sarcoplasmic tubules which pump Ca++ + E , ATP , ADP gliding of actin over myosin Muscle contraction .

Cardiac Muscle

Cardiac Muscle located only in the heart muscle fibers joined together by intercalated discs fibers branch network of fibers contracts as a unit self-exciting and rhythmic longer refractory period than skeletal muscle

cardiac sarcoplasmic reticulum Cardiac T-tubules are present at the Z lines and not at the A band, I band junctions. -The cardiac sarcoplasmic reticulum is not well developed, and consequently Diads and not Triads are common in cardiac muscle. -Cardiac T-tubules are associated with only one expanded terminal sarcoplasmic reticulum cisterna.

Smooth muscle

smooth muscle 1-Smooth muscle cells are fusiform or spindle-shaped, large at the middle part and taper towards the ends. 2-Each smooth muscle cell has a centrally located elongated nucleus which becomes cork screw-shaped during contraction. 3-The smooth muscle is surrounded by an external lamina and reticular fibers.

Sites and functions of smooth muscle 1-In the walls of hollow viscera such as the uterus, vas deferens and ureters, smooth muscle regulate the size of the lumen. 2-In the walls of the intestine, smooth muscle generate rhythmic peristaltic movements 3- In the iris of the eye, smooth muscle produce precise and graded contractions. 4-In the blood vessels, smooth muscle can synthesize collagen, elastin and proteoglycans