肺结核.doc

PULMONARY TUBERCULOSIS General Considerations: Tuberculosis isa chronic infection ,potantially of lifelong duration,caused by two species of mycobacteria and, rarely, . Which causes nodular, caseating granuloms called tubercles that fibrose,ulcerate or calcify. The disease is confined to the lungs in most patients but may spread to almost any part of the body. Etiology: The tubercle bacillus () is aerobic, non-motile,non-spore-forming, high in lipid content, and acid and alcohol-fast. It grows slowly and differs form other mycobacteria by its ability to produce niacin. Pathogenesis: Tuberculosis is transmitted by airborne droplet nuclei (containing tubercle bacilli) Many droplet nuclei are capable of floating in the immediate environment for several hours. Large particles may be inhaled bya person breathing the same air and impact on the trachea or wall of the upper airway As the bacilli multiply, they spread through lymphatic channels to regional lymph nodes, and through the blood stream to the rest of the body Immunity and Tuberculin Hypersensitivity: The bacilli within 4 to8 weeks after infection cellular immunity develop, so that the macrophages are "activated" and are capable ofnot only phagocytizing but also killing anisms. Coincident with tfae development of cellular immunity, the delayed type of skin hypersensitivity to tuberculoprote