Muscle Tissue:

A muscle tissue arises from the embryonic mesoderm. Structure: All muscles are made up of elongated and thin cells called muscle fibres. The cytoplasm of muscle fibres is known as sarcoplasm that contains a network of membranes called sarcoplasmic reticulum. A muscle fibre may be bounded by a specialized membrane called sarcolemma. Each muscle fibre may contain one or more nuclei. The position of nuclei is variable in different types of muscle fibres. Each muscle fibre may contain numerous thin myofibrils arranged along the long axis of the fibre. Function: Muscle tissue brings about movements of the body parts and helps the organism in locomotion, also responsible for the passage of food through the alimentary canal, Muscles perform important functions such as in ingesting food, in passing urine and in moving the sense organs such as eyes, nose, pinnae and in the maintenance of equilibrium and in posture and play important role in the facial expression and gesture.

Types of Muscle Fibres:

Image showing types of muscle fibres.

Striated/Skeletal muscle

Unstriated/smooth muscle

Cardiac muscle

Location

Attached to the bones, in the head, trunk and limb region and also found in the tongue and pharynx

Located in the walls of visceral organs such as intestinal, genital, urinary and respiratory organs and the walls of the blood vessels

Found in the walls of the heart

Shape

Elongated, narrow, cylindrical, and unbranched fibres with blunt ends, Myofibrils of striated muscle fibre show alternate dark and light cross bands

Spindle shaped cell, tapering at both ends, round or polygonal in cross section, sarcoplasm contains numerous fine longitudinally arranged thread like myofibrils

Elongated, cylindrical, branched. The fibres show faint but regular cross striations due to the presence of myofibrils that contain action and myosin filaments

Sarcolemma

Thin and tough membrane sarcolemma of the fibre (cell). Each muscle fibre is bounded by an elastic sheath, the sarcolemma

Thin cell membrane, muscle cell lacks definite membrane comparable to sarcolemma of striated muscle.

Thin

Nucleus

Multinueated that are peripheral to their fibers

Uninucleated at the center

One nucleus per cell at the center

Blood Supply

Rich

Poor

Rich

Intercalate Discs

Absent

Voluntary controlled

Absent

Involuntary controlled

Present

Involuntary controlled

Responsible

For the movement of the skeleton and muscles

For the movement of substances such as food and blood

For moving blood in the heart

The muscle fibres have the following characteristics: Excitability (respond to stimulus), Extensibility (stretch), Contractility (contract) and Elasticity (move back to the original position).

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