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Muscle Muscle TissuesTissues

Prof. Dr. ASHRAF M. Prof. of Histology

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Muscle Muscle TissuesTissuesGeneral

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

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Types of Muscle Types of Muscle TissueTissue

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)

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Muscle Muscle TissuesTissues

Skeletal Muscle Smooth Muscle

Cardiac Muscle

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types 0f the types 0f the musclesmuscles

A- Skeletal, Striated and Voluntary.

B- Cardiac, Striated and Involuntary.

C- smooth non-striated &Involuntary

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Connective Tissue Connective Tissue CoveringsCoverings

• epimysium• perimysium• fascicles• endomysium

• muscle• fascicles• muscle fibers• myofibrils• thick and thin filaments

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Type of skeletal muscle Type of skeletal muscle fibresfibres

Red muscle fibres White muscle fibres : Intermediate muscle fibres

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RedRed muscle muscle fibresfibres

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

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WhiteWhite muscle muscle fibres fibres

•regular striations . •less myoglobin , mitochondria . •quick , short contractions , •easily fatigued .

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InterIntermediate mediate muscle muscle fibres 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 .

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Structure of a Skeletal Structure of a Skeletal MuscleMuscle

Skeletal Muscle

• organ of the muscular system•skeletal muscle tissue

Skeletal muscle is also called voluntary muscle since it is under voluntary control.

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Skeletal muscle Skeletal muscle fibersfibers

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

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Skeletal muscle Skeletal muscle fibersfibers

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.

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Skeletal muscle Skeletal muscle fibersfibers

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Skeletal muscle Skeletal muscle fibersfibers

The dark bands are The dark bands are Anisotropic Anisotropic

( A-bands ( A-bands ) .) .

The light bands are The light bands are IsotropicIsotropic

( ( I – bands I – bands ) .) .

The ( A ) band show a The ( A ) band show a pale pale areaarea in its center in its center = H- zone = H- zone divided by a dark divided by a dark line = M line = M . .

The ( I ) band show a The ( I ) band show a dark dark line line in its center in its center = Z- line = Z- line . .

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Triad of tubular Triad of tubular system 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 .

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Triad of tubular Triad of tubular system 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 .

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Cardiac Cardiac MuscleMuscle

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Cardiac MuscleCardiac 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

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cardiac sarcoplasmic cardiac sarcoplasmic reticulum 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.

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Smooth Smooth musclemuscle

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smooth smooth musclemuscle

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.

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Sites and functions of Sites and functions of smooth musclesmooth 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