Types of Muscles and Their Functions

Muscles are the [tag-tec]contractile tissues[/tag-tec] that are responsible for performing various voluntary and involuntary functions. We would have a general discussion about different muscle types in this article.Muscles are so named because, many of them resemble a mouse, with their tendons representing the tail. In Latin Mus stands for mouse.

By definition Muscle is a contractile tissue which brings about [tag-tec]movements[/tag-tec]. Muscles can be regarded as motors of the body.

Types of Muscles

The muscles are of three types, skeletal, smooth and cardiac. The characters of each type are summarized below.

Skeletal muscles

They are also called striped, striated, somatic, or voluntary muscles. These muscles are most abundant, found attached to skeleton.

They exhibit cross-striations under microscope, and are considered to be the best differentiated form of muscle.They are supplied by somatic (cerebrospinal) nerves, and, therefore, are under voluntary control, with certain exceptions

They respond quickly to stimuli, being capable of rapid contractions, and, therefore, get fatigued easily and help in adjusting the individual to external environment.

Skeletal muscles are under highest nervous control of cerebral cortex and Each muscle fibre is a multinucleated cylindrical cell, containing groups of myofibrils (Cohnheim’s areas) which, in turn, are made up of myofilaments of three types (myosin, actin and tropomyosin), the actual contractile elements.

uscles of limbs and body wall, and bronchial muscles are examples of skeletal muscles.

Smooth Muscles

They are also called plain, unstriped, non-striated, visceral, or involuntary muscles. These muscles often encircle or surround the viscera

Smooth muscles do not exhibit cross-striations under microscope, being plain and smooth in form

They are supplied by autonomic nerves, and, therefore, are not under voluntary control and respond slowly to stimuli.

Smooth muscles are capable of sustained contraction, and, therefore, do not fatigue easily.

They provide motor power for regulating the internal environment related to digestion, circulation, secretion and excretion.

Smooth muscles are less dependent on nervous control, being capable of contracting automatically, spontaneously, and often rhythmically and each muscle fibre is an elongated, spindle-shaped cell, with a single nucleus placed centrally; the myofibrils show longitudinal striations.

Muscles of the blood vessels, and the arrector pili muscles of the skin are examples of smooth muscles.

Cardiac Muscle

Cardiac muscle fibers form myocardium of the heart. It is intermediate in structure, being striated and at the same time involuntary. It is meant for automatic and rhythmic-contractions and each muscle fibre, having a single nucleus placed centrally centrally branches and anastomoses with the neighbouring fibres at intercalated discs (apposed cell membranes); the cross-striations are less prominent than those in the skeletal muscle.

Myoepithelial Cells

These are present at the bases of secretary acini of sweat gland, etc. These help in expulsion of secretion from the acini.

Out of the four kinds of muscles, the skeletal muscles are most abundant in the body. These are the only muscles which are dissected out in the dissection hall and studies individually.