3.7
肺结核 II:病理生理学
结核病（TB）是一种由结核分枝杆菌引起的细菌性传染病。虽然结核病主要影响肺部，导致肺结核，但它也可能影响其他各种器官，这种情况称为肺外结核病。
以下是其病理生理的详细解释:
传播:当人吸入含有结核分枝杆菌的飞沫核时，传播过程就开始了。当患有肺结核或喉结核的人咳嗽、打喷嚏或说话时，这些飞沫核通常会释放…
结核病的发病机制始于易感宿主吸入含有结核分枝杆菌的气溶胶滴。
这些微滴到达肺部的肺泡，在此处细菌大量繁殖，并与肺泡巨噬细胞相遇，后者会吞噬这些细菌。
然而，巨噬细胞并未杀死这些细菌，而是允许其在细胞内存活并进行复制。
经过2至6周后，机体启动细胞介导的免疫反应，形成一种称为肉芽肿的特殊结构，以限制细菌的扩散。
肉芽肿由免疫细胞、活的和死亡的细菌细胞、T细胞以及巨噬细胞组成。
细菌可在肉芽肿内保持休眠状态，不引起任何症状，且不具传染性。此阶段称为潜伏性结核感染。
如果免疫系统受损，潜伏性结核病可通过干酪样坏死过程发展为活动性结核病，此时肉芽肿的中心发生坏死，形成一种称为干酪样物质的奶酪样物质。
这种干酪样物质随后侵蚀支气管，形成空洞，从而促进细菌快速增殖，并可能通过血液或淋巴传播感染。
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Q1: How does Mycobacterium tuberculosis survive inside alveolar macrophages?
When susceptible hosts inhale aerosolized droplets containing Mycobacterium tuberculosis, the bacteria reach the lungs' alveoli where alveolar macrophages engulf them. However, instead of destroying the bacteria, the macrophages allow them to survive and replicate within. This intracellular survival mechanism enables the infection to establish and persist in the host.
Q2: What is a granuloma and why does the body form one?
A granuloma is a specialized immune structure that forms 2-6 weeks after infection when the body initiates a cell-mediated immune response. It comprises immune cells, live and dead bacterial cells, T-cells, and macrophages clustered together. The granuloma's primary function is to contain and prevent the spread of Mycobacterium tuberculosis throughout the body.
Q3: What is the difference between latent and active tuberculosis infection?
In latent tuberculosis infection, bacteria remain dormant within the granuloma, causing no symptoms and being non-contagious. Active tuberculosis disease develops when the immune system is compromised, allowing bacteria to multiply and spread, causing tissue damage and symptoms. About 5-10% of individuals with latent TB infection progress to active disease, particularly if their immune system becomes weakened.
Q4: How does caseation lead to cavity formation in tuberculosis?
Caseation occurs when the center of a granuloma becomes necrotized, forming a cheese-like substance called caseum. If this caseous material erodes into a bronchus, it creates a cavity that facilitates rapid bacterial proliferation. This cavitation process worsens symptoms and increases the potential for bacterial spread through blood or lymph.
Q5: How is tuberculosis transmitted from one person to another?
Tuberculosis transmission begins when a person inhales droplet nuclei containing Mycobacterium tuberculosis. These droplets are typically released into the air when an individual with pulmonary or laryngeal TB coughs, sneezes, or speaks. The inhaled bacteria then reach the alveoli in the lungs, where the infection cycle begins.
Q6: What role does the cell-mediated immune response play in tuberculosis infection?
Approximately 2-6 weeks post-infection, the body mounts a cell-mediated immune response where T cells recognize mycobacterial antigens presented by infected macrophages. This triggers cytokine release, activating other immune cells and processes that lead to granuloma formation. This immune response aims to contain bacterial spread and is essential for controlling the infection.
Q7: Can tuberculosis spread to organs outside the lungs?
Yes, from the lungs, Mycobacterium tuberculosis can spread through the bloodstream, causing miliary TB, or through the lymphatic system to other organs, resulting in extrapulmonary tuberculosis. This dissemination occurs when bacteria escape the primary infection site and establish secondary infections in various body systems, complicating the disease presentation and nursing management and prevention strategies.