Tuesday, July 11, 2017

TYPES OF MUSCLES

Types of Muscles
Muscles can be classified on various criteria namely location, appearance, nature of regulation of their
activities. Based upon location, the muscles can be of following types
(I) Skeletal muscle or striped or striated or voluntary muscles : These muscles are attached to the
skeleton component of the body and are primarily involved in the locomotory actions and changes of the
body Posture. When observed under a rnicroscope, alternate light and dark bands are observed on the
muscle fibres. Due to the striated appearance of the muscle fibres, these muscles are called striated or
striped muscles. These muscles are voluntary as they are under the control of animals will or conscious.
For example, muscles of hind[imbs, forelimbs, body wall, tongue, pharynx and beginning of oesophagus etc.
(ii) Smooth or non-striated or non-striped or involuntary muscles The cells of these muscles are
elongated, spindle-shaped, broad from the middle and have tapering ends. These muscles do not have
alternate hght or dark bands on their muscle fibers and hence give a smooth appearance when observed
under a microscope. Their fibres are not organised into parallel arrays.

These muscles lines the hollow organs and are involuntary-e. g., posterior region of oesophagus, stomach,
intestine, lungs, urinary bladder, urinogenital tract. The transportation of food through the digestive tract
and gametes through the genital tract occurs due to the contraction of smooth muscles.
(iil) Cardiac muscle : Cardiac means heart, hence muscles of the heart are called cardiac muscle. The cells
of cardiac muscle assemble in a branching pattern. These are striated in nature I. e., alternate light and
dark bands could be observed on the muscle fibre when kept under the microscope. These are involuntary
in nature as they generate their own impulse or excitation and hence allow heart to continue its pumping
activity of rhythmic contraction and relaxation. These are meant for increasing and decreasing the rate
of muscular activity.