The Probert Encyclopaedia of Medicine

THE CAUSE OF BLEEDING

Blood may escape from the blood vessels as a result of injury. Capillaries are fractured by simple abrasion, veins with their very fragile walls are easily torn, while arteries are usually injured by a cut, either accidental or intentional. Infective or malignant disease, as it eats its way through tissues, may invade the wall of a blood vessel which subsequently gives way allowing free escape of blood. In the case of capillaries and veins, the inflammatory process involving the vessel usually sets up thrombosis so that haemorrhage does not occur. With arteries, while thrombosis may sometimes occur as the result of the inflammation, severe haemorrhage frequently follows erosion. Perhaps the most common site of such arterial haemorrhage is in the base of a gastric ulcer. Because of the inflammation in the walls of the artery which may be coursing through the base of the ulcer, the vessel is prevented from contracting, and when it bursts the hole is held rigidly open with resultant severe and sometimes fatal haematemesis (vomiting of
blood). High blood pressure is frequently associated with disease of the walls of the arteries, which lose their elasticity. In most parts of the body, the arteries are surrounded by fairly firm tissues which tend to support them, but this is not the case in the brain which is the most common site for the rupture of small arteries. Such cerebral haemorrhage is responsible for one form of apoplexy. The wall of an artery may be weak from injury, from congenital defect or from disease, and instead of it bursting it develops a large bulge which continues to increase in size as the years go by. The surrounding tissues become eroded by the continuous beating of the artery and eventually the stretched-out thin-walled sac bursts. This arterial bulge is known as aneurism. A congenital form occurs near the base of the brain. Aneurism follows gun-shot wounds in the region of arteries and the aorta undergoes a similar change as the result of arterio-sclerosis or syphilis.
Research The Cause of Bleeding