d. Trauma. Trauma may be defined as injury sustained by the body as the
result of a physical agent or force. The physical agents that may produce trauma or
injury of the body are:
Light. In excessive amounts, light can cause temporary blindness.
(2) Heat. Excessive heat can cause burns of the body, heat cramps, heat
(3) Cold. Cold is absence or deficiency of heat. Exposure to low
temperatures can result in frostbite and other cold injury.
Electricity. One can sustain burns, electric shock, or both when exposed
to this agent.
(5) Ionizing radiation. Excessive exposure to x-rays or to radioactive
elements can produce burns, radiation sickness, malignancies, cataracts of the eye,
and genetic changes.
(6) Mechanical forces. These agents produce contusions, abrasions,
lacerations, fractures, sprains, and strains.
(7) Sound. Exposure to excessive noise can cause temporary or permanent
e. Circulatory Disturbances. Any interference with the blood flow to a portion
of the body results in a circulatory disturbance.
(1) Ischemia. A decrease in the normal diameter of an artery supplying a
portion of the body results in a decrease in the amount of blood that flows to the part.
The area becomes more pale and colder than normal, and is said to be ischemic.
(2) Thrombosis. Whenever a vessel wall becomes diseased, the blood
tends to collect at the diseased or injured site and form a thrombus (clot). The presence
of an intravascular blood clot is called thrombosis.
(3) Embolism. Portions of a thrombus may break loose, and then travel
freely in the bloodstream until stopped by a vessel too small for the particle to pass
through; or foreign particles, such as air bubbles or fat globules, may be introduced into
the bloodstream and travel freely until stopped by a smaller vessel. These foreign
particles are known as emboli. The process of obstruction or occlusion of a blood vessel
by a transported foreign material is known as embolism.
(4) Gangrene. When an extremity or portion thereof loses its arterial blood
supply as the result of thrombosis, embolism, trauma, or from any other cause, a