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Circulatory Anatomy, Physiology and Regulation Diagram showing Capillary System and Mechanisms of Edema Formation Diagram showing Sources of Arterial Emboli |
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Visit: Silicosis ; Silicone granulomas Silicosis, also encountered in coal miners, is caused by fine (10 micrometer or smaller) silica dust particles, which after inhalation are phagocytosed and carried through lymphatics to lymphoid tissues in the lung and hilar lymph nodes. Fibrosis develops in areas of tissue injury and inflammation wherever the silica particles reside. The fibrosis is quite extensive, leading to crippling pulmonary insufficiency and right-sided heart failure. Cardiac Path Online The persistence of fibrosis even when the patient has left the dust-laden environment responsible for this disease indicates that the silica already present perpetuates the development of fibrosis. The current popular theory concerning pathogenesis involves the ingestion of silica by macrophages, which lead to their cytolysis and release of a fibroblast-stimulating factor. The silica is reingested by macrophages and the cycle is repeated again and again. The sustained stimulation of fibroblasts leads to increased synthesis and deposition of collagen, and the formation of dense silicotic nodules and diffuse scarring. A second hypothesis holds that an immunologic mechanism based on abnormal and increased serum immunoglobulins capable of reacting with nuclear antigens may be responsible. Visit: Environmental Pathology Online ; Pulmonary Pathology Online .
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