MUSCLES

The red flesh of our body:

- Is called the skeletal muscles because anatomically they are attached to the skeleton.

The fleshy part of the muscle is called belly. It has

two ends which are called attachments.

Skeletal muscles as the name implies are attached mainly to bones. They may be also, attached to cartilage, ligaments, skin or other muscles.

Their attachment may be:

a)    Directly through the muscular tissue itself.

b)   Through fibrous structures called tendon or aponeurosis

A tendon is the ribbon-like, rounded, or short stout white fibrous tissue.

Aponeurosis is the flattened, expanded, sheet-like white fibrous tissue.

c)   Through a combination of both fleshy and fibrous
structures.

Each muscle is attached at both of its ends. The relatively fixed attachment is called the origin while the relatively movable one is called the insertion.

Some muscles cross only one joint and so act on only this joint. They are called uni-articular.

Some muscles cross two joints and so act on two joints. These are called bi-articular.

Some muscles cross more than two joints. These are called multi-articular.

Movements Produced by Muscle Contraction:

(Figs. 7,8)

Flexion is the approximation of two surfaces or the bending or the making of an angle. (- Extension is the opposite (straightening). It is the return

back from flexion. – Abduction is the movement away from the central axis of

the body or of a limb. -Adduction  is  the opposite to abduction.  It  is the movement towards the central axis of the body or of a limb.

-  Medial rotation is the rotation towards the median plane.

-  Lateral rotation is the rotation away from the median plane.

But in the forearm these medial and lateral rotations are known respectively as pronation and supination. And in the foot thev are known respectively as. inversion and tversion.

-  Circumduction is the circular combination of the above movements.

Classification of muscles according to the arrangement their muscle fibres (form of muscles):

According to the arrangement of their fibres, muscles are classified into three main types.

1. parallel type (Fig. 9): in which the muscle fibres are long parallel fibres extending along the whole length of the tnuscle from one end to the other.