Page 28 - ASOP ROT Study Guide

means "joint disease" but has come to mean a wearing of the joint. It is commoner in old age, but
not all old people have arthritis. Therefore arthritis is not inevitably caused by joints ageing. The
truth is that we do not know why arthritis occurs in most cases. In general, as wear is the same in
those with arthritis as those without, then the problem must lie with the repair process. Despite
much research in this field, the cause of this breakdown of normal repair is still obscure.

When the cause of arthritis is unknown it is termed PRIMARY arthritis. There are, of course,
known physical and pathological factors that contribute to arthritis. These factors are generally
related to damage, where wear is more easily recognized and understood. Such arthritis is known
as SECONDARY arthritis. Secondary arthritis may be caused by:

♦ birth abnormalities - e.g.. congenital dislocation of the hip,
♦ inflammatory changes - e.g.. tuberculosis; untreated infection; rheumatoid arthritis,
♦ metabolic upsets - e.g.. gout, and trauma - e.g.. a badly united fracture involving a joint.

5. THE MUSCULAR SYSTEM

The muscular system consists of the muscles and their associated tissues such as tendons. If
any part of your body moves, muscle moves it. The main function of the muscular system is to
cause movement.

5 . 1 Types of Muscle Tissue

Muscle tissue may be classified into three types depending on the structure of its cells and its
function.

1. Smooth muscle tissue is not involved with locomotion. Its main action is to provide low
power rhythmic contractions over long periods of time. For example, in the digestive
system smooth muscles are found in the walls of the gut providing the contractions
needed to push food materials along its length. In the cardiovascular system, smooth
muscle is found in the walls of blood vessels where it plays a part in controlling blood
flow.

2. Skeletal muscle tissue is found in skeletal muscles. Skeletal muscles make up 30-40%
of body weight and are responsible for movement and controlling body posture. It is
also called striated muscle because the cells appear striped under the microscope due
to the alignment of the filaments (tiny fibers) within the cells. Smooth muscle does not
have these "stripes".

3. Cardiac muscle tissue is found in the wall of the heart. It is striated but the shape and
arrangement of the muscle cells is different from skeletal muscle tissue. The function of
cardiac muscle is to contract regularly causing the heart to pump.

We do not have voluntary control over the actions of smooth muscle and cardiac muscle in the
same way as we control the actions of skeletal muscles.