What Are Muscles? Functions and Types of the Muscular Tissues

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muscular system
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Muscles

Motion (i.e., capability to move) is an essential body function of all animal organisms. Movements of the body as a whole, brought about by muscles because they possess the property of contraction and relaxation. The muscles composed of mainly of muscular tissue which, like other tissues of the body, consists of cells and intercellular substance. The cells of the muscular tissue are very much elongated. Therefore, generally refers to as muscle fibers. The muscle cells are also sometimes referring to as myocytes.

Functions of Muscles

By their contraction, the muscles of body perform three important functions:

1. Production of movements

2. Maintenance of posture

3. Heat production

Production of movements.

motion is an essential body function. Contraction (end relaxation) of muscles leads to locomotive movements of whole of the body like walking and running. Many other movements produced by muscles are less noticeable, e.g., beating of the heart, pushing of the faces through the intestine, and contraction of the urinary bladder to expel the urine.

Maintenance of posture.

 Contraction of the muscles holds the body in stationary positions like standing and sitting.

Heat production.

Muscle contractions produce heat and thus play an important role in maintaining normal body temperature.

Types of Muscular Tissues

Generally, the muscular tissue is classified into three main types: (1) skeletal muscle, (2) smooth muscle, and (3) cardiac muscle.

It must however, be noted that there is no common basis for the classification of muscular tissue.

The name of first variety (skeletal muscles) is on the basis of its attachment to the skeleton. The name of the second type (smooth muscle) is based upon its microscopic structure. The third variety (cardiac muscle) is titled on the basis of its location in the body (cardiac is a Greek word meaning pertaining to heart). Developmentally, all the three varieties of muscle tissue, i.e., skeletal, smooth and cardiac, derived from the mesoderm except the smooth muscle of the iris, which develops from the ectoderm.

Skeletal Muscles

This type of muscle tissue is the most abundant of all varieties and constitutes about 40% of the total body weight. As indicated by their title. muscles of this type attaches to different component of the skeleton (bones and cartilages). When examined under microscope, the skeletal muscle fibers seen as elongated, non-branching, multinucleated cells that show transversely arranged alternating dark and light bands which give these cells a conspicuously striated appearance. Although the cardiac muscle shows cross striations (vide infra), the striated appearance regarded to a characteristic feature of the skeletal muscle. This generally, the term striated muscle regards to analogous with skeletal muscle.

Functionally, the skeletal muscle also titled as voluntary muscle because it can make to contract by conscious control. However, some skeletal muscles involves in production of movements that operates at an unconscious level, e.g., breathing, blinking and swallowing, etc. However, some skeletal muscles of the head and neck region which develop from the branchial (pharyngeal) arches designate as special visceral muscles, e.g., muscles of mastication, muscles of facial expression, and muscles of larynx, etc.

Smooth Muscle

As indicated by its name, the smooth muscle tissue is not striated and, therefore appears “smooth” under the microscope. Each smooth muscle fiber is a long, slender, spindle-shaped cell containing a single nucleus, which is located in the central wider part of the cell. As mentioned above, no cross-striations are visible in the smooth muscle cells; hence this variety of muscle tissue is also known as non-striated muscle. Unlike skeletal muscle, the smooth muscle is not connecting to bones. Instead, the smooth muscle fibers usually form sheets in the walls of the hollow organs, e.g., blood vessels, gastrointestinal tract, respiratory tract and urogenital tract. Because of its location in the walls of the hollow viscera, the smooth muscle is also titled as visceral muscle.

Cardiac Muscle

Cardiac muscle tissue is found only in the wall of the heart where it is known as myocardium. The cardiac muscle fibers are made up of short, cylindrical segments (cells) joined end to end by intercellular junctions.

Each segment contains one nucleus located in the central region of the cell. The cardiac muscle cells also show cross-striations due to the presence of alternating dark and light bands. However, the striations are not as distinct as those of the skeletal muscle. A special feature of the cardiac muscle cells is that they give off branches which make junctions with the branches of the neighboring cells and, thus, convert the whole myocardium into a network. Like the smooth muscle, the cardiac muscle is also involuntary and receives its nerve supply from the autonomic nervous system.

Sajid Saleem
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Sajid Saleem

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5 thoughts on “What Are Muscles? Functions and Types of the Muscular Tissues

  1. good

  2. NYC work

  3. Good

  4. · May 26, 2021 at 5:38 pm

    capability to move is an essential body function of all animal organisms.👍👍

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