MUSCULAR TISSUES

There are types of muscles:-

- Skeletal muscles fibers.

- Cardiac muscles fibers.

- Smooth muscle fibers.

Skeletal muscles

- They are striated and voluntary muscles.

- Under the microscope, the cells show

transverse dark and light bands.

- They are attached to the skeleton, so, their

contraction move the skeleton.

- Sk. M. formed of elongated cells (muscle fibers)

and connective tissue in between.

- Loose CT arranged around and in between

muscles fibers and bundles.

- CT carries blood vessels, lymphatics, and

nerve fiber to muscle.

The connective tissue component

- The connective tissues are arranged as:-

- Epimysium: the outer coat of the muscle.

- Perimysium: around the muscle bundles and fascicles.

- Endomysium: between each muscle fiber.

The connective tissue component

Skeletal muscle fiber

- The muscle fiber is long and cylindrical in

shape.

- The nuclei are multiple, long and

peripheral.

- The cytoplasm show alternative dark and light

striations.

- The dark band is called anisotropic or

A- band.

- The light band is called isotropic or

I - band.

- In the middle of the dark A band there is

a pale region called H-zone.

- In the middle of the light band there is a

dark line called Z- line.

- The distance between two successive Z lines

is called Sarcomere.

- Sarcomere is the functional unit for muscle

contraction.

Myofibrils

- The cytoplasm or sarcoplasm is full of parallel

myofibrils, which are formed of two types of

fine myofilaments:-

- Thick myosin filaments in the A-bands.

- Thin actin filaments in the both I & A

bands.

-The arrangements of actin and myosin filaments

give the myofibrils their striation.

Motor unit: group of muscle fibers innervated by

collection of individual nerve branches within

muscle.

Neuromuscular junction: required for growth and

determines type of metabolism (red or white

fibers) by frequency of impulses,

any one motor nerve supplies fibers of one type

only; all fibers of particular motor unit are of

same metabolic type.

Neuromuscular junction (motor end plate):

contains concentration of mitochondria and rER

Cardiac muscle

- Cardiac muscle is striated involuntary muscle.

- The sarcoplasm containing a single, oval,

prominent and central nucleus.

- The muscle fibers are shorter than skeletal

muscle fibers and branched.

- The short cardiac muscle fibers are joined

together by intercalated discs.

- These discs appear as dark lines.

Smooth muscles

- Visceral involuntary muscle fibers.

- It is smooth because there are no striation.

- The cytoplasm is full of actin and myosin filament.

- The cytoplasm is acidophilic with central and single nucleus.