MUSCLE TISSUE

Muscle Tissue 

• If it contracts, it's muscle:• Muscle tissue is categorized on the basis of a

functional property: the ability of its cells to contract.

• consists of the contractile protein fibrils actin and myosin. Muscle is responsible for movement of the body and changes in the size and shape of internal organs.

• Muscle cells are generally referred to as muscle fibres.

• Muscle fibres are typically arranged in parallel arrays allowing them to work together effectively

The three types of muscle:

Three types of muscle tissue can be identified histologically:

1.1. skeletal muscle skeletal muscle (striated muscle, voluntary),

2.2. cardiac musclecardiac muscle3.3. smooth muscle smooth muscle (non-

striated muscle, involuntary).

Skeletal muscle

• Skeletal muscle constitutes the muscle that is attached to the skeleton and controls motor movements and posture.

Skeletal Muscle

• Skeletal muscle fibres (cells) are multinucleated

• They are filled with longitudinally arrayed subunits called myofibrils.

• The myofibrils are made up of the myofilaments myosin (thick filaments) and actin (thin filaments).

• The striations reflect the arrangement of actin and myosin filaments and support structures.

• The individual contractile units are called sarcomeres.

Skeletal Muscle Summary

Summary: Skeletal muscle fibres bear obvious striations, have many peripherally located nuclei, are of the same thickness throughout their length and do not branch.

Skeletal Muscle

Skeletal Muscle

Cardiac Muscle

• Cardiac muscle is the type of muscle found in the heart

• Cardiac muscle is intrinsically contractile but is regulated by autonomic (unconscious) and hormonal stimuli.

Cardiac Muscle Summary

• Striations are present (actin and myosin)• Greater number of mitochondria present• Cardiac muscle cells have only one or two

nuclei, which are centrally located. • Cardiac muscle cells are joined to one

another in a linear array. The boundary between two cells abutting one another is called an intercalated disc.

• Cardiac muscle fibres are branched

Cardiac Muscle

Cardiac Muscle

Smooth Muscle

• Smooth muscle is the intrinsic muscle of the internal organs, iris of the eye and blood vessels.

• Like cardiac muscle, smooth muscle fibres are intrinsically contractile but responsive to autonomic and hormonal stimuli. They are specialized for slow, prolonged contraction.

Smooth Muscle

• Smooth muscle fibres are generally arranged in bundles or sheets (no striations)

• A single nucleus is located in the central part of the fibre.

• Fibres do not branch. • Smooth muscle fibres lie over one another

in a staggered fashion • Fusiform Shape with tapered ends

Smooth Muscle

Musclel Tissue Summary

Muscle Tissue Summary