Functions1.Movement -Whole body or

parts of the body2.Maintenance of body

posture.3.Separates body cavities.4. Respiration.

Muscular Tissue

In animals there are two principle types of muscles:

1.Striated muscles –their cells exhibit cross striations under light microscopy. Based on the location striated muscles are further divided into:

a. Skeletal muscle

b. Cardiac

2. Smooth muscle. These cells have no cross striations.

Myocytes / Muscle cells

These are the cells of the muscle tissue.

They are elongated cells whose primary role is contraction.

Skeletal Muscle• Skeletal muscles are anchored

by tendons or by aponeurosis to bone.

• Responsible for movement of the skeleton, maintenance of body posture.

• Voluntary-control of will.• Components of skeletal muscle

tissue.a. Muscle cells. These are long

unbranched cells (run parallel) or myofibres. Have several peripherally located nuclei.

b.Supportive connective tissue.

• The skeletal muscle cells are multinucleated. Their nuclei are located in the cytoplasm immediately beneath the plasma membrane=sarcolema

• Each myofibre appears striated.

• That is, they have periodic transverse bands.

• Within a myofibre are myofibrils.

Skeletal muscle-longitudinal and transverse sections.

MyofibrilsThis is the basic contractile unit.

Several myofibrils are located within a muscle fibre.

They give the muscle fibre the appearance of cross striations.

• They are made up several sarcomeres each of which runs from one z band to the next.

• They extend the entire length of a muscle cell.

• When muscle contracts each sarcomere shortens and thickens.

Myofilaments• These are the actual contractile elements

of skeletal muscle. Bundle of myofilaments make a myofibril.

• Two types of myofilaments are associated with muscle contraction.

• 1. Thin filaments. Composed of protein actin

• 2. Thick filaments. Composed of protein myosin II.

• The two myofilaments occupy most of the cytoplasm =sarcoplasm.

Cross striations• Arrangement of thick and thin

filaments results in the different densities in the sarcomere=cross striations.

• Under the light microscope, they appear as alternate light and dark bands=termed as A band and I bands.

• The A and I bands are bisected by narrow regions of contrasting density.

• The light I band is bisected by the Z line while the thick A band is bisected by the M band.

Skeletal muscle cells- Longitudinal section

Connective tissue in Muscle

Several myofibres are grouped together to form a fasciculus (bundle).

• Myofibre- endomysium

• Fasciculus- perimysium

• Whole muscle- epimysium

Cardiac muscle tissue• It is found in the heart.

• Controlled by the autonomic nervous system (ANS)-involuntary.

• 1. Muscle has short striated cells.

• 2. Fibres branch and anastomose with adjacent fibres.

3. Each cell has 1-2 nuclei

which are centrally

located unlike the skeletal

muscles where the cells are

multinucleated with their

nuclei located below the plasma membrane.

4. Have intercalated discs which are specialized intercellular junctions where one cell touches another cell. They appear densely staining under the light microscope.

–During Increased demand the cardiac cells can hypertrophy.

–During decreased demand the muscle undergoes atrophy

Cardiac muscle tissue

Intercalated discs

Intercalated discs

PURKINJE FIBERS• Specialized cardiac fibers.

• Involved in impulse conduction to the various parts of the myocardium.

• Larger than the cardiac muscle cells.

• Myofibrils in these fibres are fewer than in the typical cardiac muscle. They are star-like in shape.

• They are lighter staining when compared with normal cardiac cells.

PURKINJE FIBERS (cross-section)

Cardiac cells

Purkinje fibres

Smooth Muscle Tissue• Location

• They line blood vessel walls, the stomach, the intestines and urinary bladder.

• They are involuntary.

• They have no cross striations.

• They are referred to as either;

– Smooth, un-striped , visceral or plain muscles.

Structure

-Smooth muscle is formed by union of spindle shaped cells. The cells are elongated and taper on both ends.

- The nuclei are centrally located.

-The cells are interconnected by gap junctions.

Smooth Muscle cells -Longitudinal section

a).

b).

Smooth Muscle cells – Longitudinal & cross section

Skeletal muscle cardiac muscle smooth muscle

Location

Muscles of the skeleton, tongue, oesophagus and diaphragm.

Heart, superior and inferior vena cava, pulmonary veins.

Blood vessels, intestines, stomach.

Fiberslong and unbranched

Short and branching

spindle

NucleiFew and peripheral

Single and central

Single and central

Sarcomeres present present None

Cell to cell junctions

NoneIntercalated discs.

Gap junctions