MUSCULAR TISSUEMUSCULAR TISSUE-: -: There are three types of muscular tissues in the There are three types of muscular tissues in the

body, these arebody, these are-: -: 11--Skeletal muscleSkeletal muscle..22--Cardiac muscleCardiac muscle..33--smooth musclesmooth muscle..

All these types of muscles consist of the following All these types of muscles consist of the following structuresstructures: :

11--Muscle fibersMuscle fibers..22--Cytoplasm of the muscle is known as Cytoplasm of the muscle is known as

sarcoplasmsarcoplasm..33--Cell membrane is known as sarcolemmaCell membrane is known as sarcolemma..

44--Each sarcoplasm contain numerous myofibrils Each sarcoplasm contain numerous myofibrils which contain two types of contractile protein which contain two types of contractile protein filaments actin &myosinfilaments actin &myosin

1-Skeletal muscle :These are cylindrical long & multi nucleated cells with peripheral nuclei.

*The muscle fibers consist of sub units called myofibrils that extend along the muscle fiber.

*Each myofibrils consist of myofilaments formed by contractile thin protein called Actin & and thick protein called myosin.

*The arrangement of actin &myosin in the skeletal muscle is very regular and appear in the light microscope as a light (I bands) and dark (A bands) in each muscle fiber give the

muscle cross striation appearance.

Therefore it is known as striated muscles.

*Each I band bisected by dense transverse Z line, between each two Z lines there are the smallest contractile unit called the sarcomere.

*Skeletal muscle is surrounded by a dense irregular connective tissue layer called epimysium.

From the epimysium ,less dense irregular C.T. layer called perimysium extends and divides the muscle into smaller bundles called Fascicles, then thin layer of reticular C.T. called endomysium separate the individual fiber, in the C.T. that separate the muscle into fascicles there are the blood & nerves and lymphatics.

*This muscle is voluntary.

Skeletal muscle

Skeletal muscle

muscle fiber

Peripheral nucleus

Skeletal muscle

Cross striation

Skeletal muscle cross section

2-Cardiac muscle:-This also cylindrical, this muscle locate the wall & septa of the heart and the largest blood vessel attached to the heart(aorta & pulmonary trunk).

This muscle also exhibit the cross striation due to regular arrangement of actin and myosin which form the I light bands and a thick bands.

*It contain central nuclei and it is in voluntary muscles.

*The fibers of this muscle shows end to end junction and the site of junction appear dark line known as intercalated disk

Cardiac muscle

Cardiac muscle

Cardiac muscle

Intercalated discs

Cross striation

Central nucleus

Cardiac muscle cross section

Smooth muscles-:These are voluntary muscles present in the hollow organs like intestine,ureters, esophagus…etc.

Unlike the other two types of muscles the arrangement of actin &myosin are irregular in the muscle fiber therefore it appears not striated.

*The muscle fibers are spindle in shape & shows central nuclei.

Smooth muscle

Smooth muscle

Smooth muscle