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Hemorrhage (i.e. bleeding) is a discharge of blood from the vascular compartment to the exterior of the body or into nonvascular body spaces. The most common and obvious cause is trauma - usually accidental, but often by the surgeon's scalpel. A blood vessel may be ruptured in ways other than laceration. For instance, severe atherosclerosis may so weaken the wall of the abdominal aorta that it balloons to form an aneurysm, which then bleeds into the retroperitoneal space. The aneurysm may complicate a congenitally weak cerebral artery (berry aneurysm) and lead to cerebral (subarachnoid) hemorrhage. Certain infections - for example, pulmonary tuberculosis erode blood vessels ; a similar vascular injury is caused by invasive tumours.
Hemorrhage also results from damage at the level of the capillaries - for instance, the rupture of capillaries by blunt trauma. Increased venous pressure also causes extravasation of blood from capillaries in the lung. Pulmonary Hemorrhage (Eg. Goodpasture's Syndrome) Vitamin C deficiency is associated with capillary fragility and bleeding, owing to a defect in the supporting structures. It is important to recognize that the capillary barrier by itself is not sufficient to contain the blood within the intravascular space. The minor trauma imposed on small vessels and capillaries by normal movement requires an intact coagulation system to prevent hemorrhage. Thus, a severe decrease in the number of platelets (thrombocytopenia) or a deficiency of a coagulation factor (Eg: Factor VIII in hemophilia) is associated with spontaneous hemorrhages unrelated to any apparent trauma. An individual may exsanguinate into an internal cavity, as in the case of gastrointestinal hemorrhage from a peptic ulcer (arterial hemorrhage) or esophageal varices (venous hemorrhage). In such case large amounts of fresh blood fill the entire gastrointestinal tract. When a large amount of blood accumulates in soft tissue, it is known as hematoma. Such a collection of blood can be merely painful, as in a muscle bruise, or fatal, if located in the brain. Diffuse superficial hemorrhages in the skin are termed purpura or ecchymoses. Following a bruise or in association with a coagulation defect, an initially purple discoloration of the skin turns green and then yellow before resolving, a sequence that reflects the progressive oxidation of bilirubin released from the hemoglobin of degraded red blood cells. A good example of an ecchymosis is a "black eye". A minute punctuate hemorrhage, usually in the skin or conjunctiva, is labelled a petechia. This lesion represents the rupture of a capillary or arteriole and is seen in conjunction with coagulopathies or vasculitis ,the latter is classically associated with bacterial endocarditis. ( Visit: INFECTIVE ENDOCARDITIS )
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FUNCTIONAL ANATOMY OF THE HEART |