Muscular System

Locomotion and bodily movements are characteristic features of the animals. The movements are effected by various cell organelles such as cilia,flagella and organs like muscles. Muscular movements are more powerful and energetic. The skeletal muscles apart from their role in smarter movements, provide beautiful shapes to the body. The inner smooth muscles of the visceral organs make them work like machines all through the life period. The muscle cells function like small motors to produce the forces responsible for the movement of the arms, legs, heart and other part of the body. Thus the highly specialized muscle tissues are responsible for the mechanical processes in the body. Based on structure, functioning and occurrence three different types of muscle tissues have been identified. They are the skeletal, visceral and cardiac muscles.

1). Skeletal muscles or striped muscles : These muscles are attached to the bones. The muscle cells are long and cylindrical. These voluntary muscles cause body movements.

2). Visceral muscles or Nonstriated muscles: These are found in the walls of the inner organs such as blood vessels, stomach and intestine. The muscle cells are spindle shaped. These are involuntary in nature.

3). Cardiac muscle : These are found in the wall of the heart. The muscle cells are cylindrical and branched. The muscles are involuntary in nature. Skeletal muscles. he skeletal muscles are attached to bones by tendons. The tendons help to transfer the forces developed by skeletal muscles to the bones. These muscles are covered by sheets of connective tissue called fascia. Tendons : These are connective tissue structures showing slight elasticity. They are like cords or straps strongly attached to bones. The tensile strength of tendons is nearly half that of steel. A tendon having 10 mm diameter can support 600 - 1000 kg.

Fascia : These are assemblages of connective tissues lining skeletal muscles as membranous sheets. The fascia may be superficial or deep. The superficial fascia is a layer of loose connective tissue found in between skin and muscles. The deep fascia are collagen fibres found as a tough inelastic sheath around
the musculature. They run between groups of muscles and connect with the bones.

Shapes of muscles:

There is a wide variety of shapes and sizes in muscles. Based on general shape and the orientation or muscle fibres in relation to the direction of pull, they can be grouped into two classes.
1. Parallel : These muscle fibres are parallel to the line of pull. The muscles may be flat, short, quadrilateral or long and strap like. The individual fibres run the entire length of the muscle.
2. Oblique : These muscle fibres are oblique to the line of pull. The muscles may be triangular or pennate (feather-like). The pennate forms may be unipennate, bipennate, multipennate or circumpennate. Some muscles have a spiral or twisted arrangement. Naming of muscles. The muscles are named according to their size, shape, position and action.

Naming of muscles :

Shape                                        Size

deltoid - triangular                 major - large
quadratus - square                minor - small
gracilis - slender                    longus - long
lattismus - broadest

Number of Heads                     Position

biceps - 2 heads                    dorsi - of the back
triceps - 3 heads                    pectoralis - of the chest
quandriceps - 4 heads            brachii - of the arm
                                              anterior, posterior.

Depth                                        Action

superficialis - superficial        extensor
internus - internal, flexor        constrictor
profundus - deep                  Flexor