📚 Lung Diseases | 肺部疾病
Lung diseases are a major topic in A-Level Biology because they show how the structure of the gas exchange system is linked to its function. This article explains the main lung diseases required by the Cambridge International AS and A Level Biology specification, including COPD, chronic bronchitis, emphysema, asthma, lung cancer, tuberculosis and pulmonary fibrosis. For each condition, we focus on causes, pathological changes, symptoms and links to smoking or infection.
肺部疾病是 A-Level 生物的重要主题，因为它们展示了气体交换系统的结构如何与功能相联系。本文解释剑桥国际 AS 与 A Level 生物大纲要求的主要肺部疾病，包括慢性阻塞性肺病（COPD）、慢性支气管炎、肺气肿、哮喘、肺癌、肺结核和肺纤维化。每种疾病都重点介绍病因、病理变化、症状以及与吸烟或感染的关系。
1. Gas Exchange and Lung Structure | 气体交换与肺结构
The lungs provide a large, moist gas exchange surface. Air travels through the trachea, bronchi and bronchioles before reaching the alveoli. Alveolar walls are only one cell thick and are surrounded by a dense capillary network, elastic fibres and a thin liquid lining containing surfactant. Oxygen diffuses from alveolar air into the blood, while carbon dioxide diffuses in the opposite direction.
肺提供大面积、潮湿的气体交换表面。空气经过气管、支气管和细支气管后到达肺泡。肺泡壁仅一个细胞厚，周围有密集的毛细血管网、弹性纤维和含表面活性物质的薄液层。氧从肺泡气扩散进入血液，二氧化碳则向相反方向扩散。
The airways are lined by ciliated epithelial cells and goblet cells. Goblet cells secrete mucus that traps dust and pathogens. Cilia beat rhythmically to move mucus upwards towards the throat, where it can be swallowed or expelled. This mucociliary escalator is a key defence mechanism.
气道内衬有纤毛上皮细胞和杯状细胞。杯状细胞分泌黏液以黏附灰尘和病原体。纤毛有节律地摆动，将黏液向上推至咽喉，再被吞咽或排出。这种黏液纤毛清除系统是重要的防御机制。
2. Smoking and Main Risk Factors | 吸烟与主要风险因素
The main risk factors for lung disease include tobacco smoking, air pollution, occupational exposure to dusts such as silica and asbestos, respiratory infections and genetic predisposition. Tobacco smoke is the most significant preventable cause of lung disease worldwide.
肺部疾病的主要风险因素包括吸烟、空气污染、职业性接触二氧化硅和石棉等粉尘、呼吸道感染以及遗传易感性。烟草烟雾是全球最可预防的肺部疾病原因。
Tobacco smoke contains tar, nicotine, carbon monoxide and many carcinogens. Tar damages cilia and stimulates goblet cells to produce excess mucus. Carcinogens such as benzopyrene can cause mutations in DNA, increasing the risk of lung cancer.
烟草烟雾中含有焦油、尼古丁、一氧化碳和多种致癌物。焦油损伤纤毛并刺激杯状细胞产生过量黏液。苯并芘等致癌物可引起 DNA 突变，增加肺癌风险。
3. COPD: Definition and Spirometry | 慢性阻塞性肺病：定义与肺量计
Chronic obstructive pulmonary disease (COPD) is a progressive obstructive lung disease mainly caused by smoking. It includes chronic bronchitis and emphysema. The airflow obstruction in COPD is not fully reversible, which distinguishes it from asthma.
慢性阻塞性肺病（COPD）是一种进行性阻塞性肺病，主要由吸烟引起，包括慢性支气管炎和肺气肿。COPD 的气流阻塞不完全可逆，这一点与哮喘不同。
Spirometry measures forced expiratory volume in one second (FEV₁) and forced vital capacity (FVC). In obstructive diseases, narrowed airways reduce FEV₁ more than FVC, so the FEV₁/FVC ratio falls. A ratio less than 0.7 is commonly used to support a diagnosis of COPD.
肺量计测定第一秒用力呼气容积（FEV₁）和用力肺活量（FVC）。在阻塞性疾病中，气道变窄使 FEV₁ 下降超过 FVC，因此 FEV₁/FVC 比值降低。FEV₁/FVC 比值小于 0.7 常支持 COPD 的诊断。
FEV₁/FVC < 0.7 → obstructive lung disease
Common symptoms of COPD include breathlessness, chronic cough, wheezing and frequent chest infections. As the disease progresses, patients may find even mild exercise difficult.
COPD 的常见症状包括呼吸困难、慢性咳嗽、喘息和反复肺部感染。随着病情进展，患者即使轻微活动也会感到困难。
4. Chronic Bronchitis | 慢性支气管炎
Chronic bronchitis is inflammation of the bronchi. It is clinically defined as a productive cough that lasts for at least three months in two consecutive years. Smoking is the most common cause because cigarette smoke irritates the airway lining.
慢性支气管炎是支气管的炎症。临床定义为连续两年中每年至少三个月的咳痰性咳嗽。吸烟是最常见病因，因为香烟烟雾会刺激气道内壁。
In chronic bronchitis, goblet cells increase in number and size, producing excessive mucus. Ciliated epithelial cells are damaged by tar, so mucus is not cleared effectively. The accumulated mucus narrows the airways and creates a site for bacterial growth, leading to recurrent infections.
在慢性支气管炎中，杯状细胞数量和体积增加，产生过多黏液。焦油损伤纤毛上皮细胞，因此黏液不能被有效清除。积聚的黏液使气道变窄，并成为细菌滋生的场所，导致反复感染。
The main symptoms are a persistent cough with sputum, shortness of breath and wheezing. Over time, chronic bronchitis contributes to the airflow limitation seen in COPD.
主要症状为持续咳嗽并伴有痰液、呼吸困难和喘息。随着时间推移，慢性支气管炎导致 COPD 中出现的气流受限。
5. Emphysema | 肺气肿
Emphysema is the destruction of alveolar walls. Inflammatory cells such as macrophages and neutrophils release protease enzymes, including elastase, which digest elastin in the alveolar walls. Smoking increases protease release and also inactivates α₁-antitrypsin, a protective enzyme inhibitor.
肺气肿是肺泡壁的破坏。巨噬细胞和中性粒细胞等炎症细胞释放蛋白酶，包括弹性蛋白酶，消化肺泡壁中的弹性蛋白。吸烟增加蛋白酶释放，同时使保护性酶抑制剂 α₁-抗胰蛋白酶失活。
When elastin is destroyed, alveoli lose their elasticity and may merge to form larger air spaces. This reduces the total surface area for gas exchange and decreases elastic recoil, making it difficult to exhale fully.
当弹性蛋白被破坏时，肺泡失去弹性并可能融合形成更大的气腔。这减少了气体交换的总表面积，并降低弹性回缩力，使完全呼气变得困难。
Patients with emphysema suffer from severe breathlessness, rapid breathing and a barrel-shaped chest caused by over-inflation of the lungs. Because gas exchange is less efficient, the blood may become poorly oxygenated.
肺气肿患者会出现严重呼吸困难、呼吸急促和因肺部过度充气造成的桶状胸。由于气体交换效率降低，血液可能出现低氧。
6. Asthma | 哮喘
Asthma is a chronic inflammatory disease characterised by reversible airway obstruction. Common triggers include allergens such as pollen and house dust mites, cold air, exercise and respiratory infections.
哮喘是一种慢性炎症性疾病，特点为可逆性气道阻塞。常见诱因包括花粉、尘螨等过敏原、冷空气、运动和呼吸道感染。
During an asthma attack, mast cells release histamine and leukotrienes. These mediators cause bronchial smooth muscle contraction, swelling of the airway mucosa and increased mucus secretion. The result is narrowing of the bronchioles, which increases resistance to airflow.
哮喘发作时，肥大细胞释放组胺和白三烯。这些介质引起支气管平滑肌收缩、气道黏膜肿胀和黏液分泌增加。结果是细支气管变窄，增加气流阻力。
Symptoms include wheezing, coughing, chest tightness and shortness of breath. Spirometry during an attack shows a reduced FEV₁ with often normal FVC, but the obstruction improves after using a bronchodilator such as salbutamol.
症状包括喘息、咳嗽、胸闷和呼吸困难。发作时的肺量计显示 FEV₁ 降低，FVC 常正常，但使用沙丁胺醇等支气管扩张剂后阻塞可改善。
7. Lung Cancer | 肺癌
Lung cancer is the uncontrolled division of epithelial cells in the bronchi or bronchioles. Carcinogens in tobacco smoke, such as benzopyrene and nitrosamines, cause mutations in proto-oncogenes and tumour suppressor genes.
肺癌是支气管或细支气管上皮细胞不受控制的分裂。烟草烟雾中的苯并芘和亚硝胺等致癌物引起原癌基因和抑癌基因突变。
A malignant tumour invades surrounding lung tissue and can metastasise through lymph or blood to other organs. Symptoms may include a persistent cough, coughing up blood, chest pain, weight loss and recurrent pneumonia.
恶性肿瘤侵袭周围肺组织，并可通过淋巴或血液转移至其他器官。症状可能包括持续咳嗽、咯血、胸痛、体重下降和反复发作的肺炎。
Epidemiological evidence shows a strong dose-response relationship between smoking and lung cancer. The longer a person smokes and the more cigarettes they smoke per day, the greater the risk.
流行病学证据显示吸烟与肺癌之间存在强烈的剂量-反应关系。一个人吸烟时间越长、每天吸烟数量越多，风险就越大。
8. Tuberculosis | 肺结核
Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis. It is transmitted through airborne droplets when an infected person coughs or sneezes. The bacteria are inhaled and reach the alveoli.
肺结核由结核分枝杆菌引起，通过感染者咳嗽或打喷嚏时产生的飞沫传播。细菌被吸入后到达肺泡。
Macrophages engulf the bacteria, but M. tuberculosis can survive and multiply inside them. The immune system forms tubercles, which are small masses of infected macrophages surrounded by lymphocytes. In many people, the infection remains dormant or primary TB is mild.
巨噬细胞吞噬细菌，但结核分枝杆菌可在其内部存活并繁殖。免疫系统形成结核结节，即由淋巴细胞包围的受感染巨噬细胞小团。许多人的感染保持潜伏状态，或原发性结核症状较轻。
Active TB destroys lung tissue and forms cavities. Symptoms include a persistent cough, coughing up blood, fever, night sweats, fatigue and weight loss. Treatment requires a long course of several antibiotics to prevent resistance.
活动性结核会破坏肺组织并形成空洞。症状包括持续咳嗽、咯血、发热、盗汗、疲劳和体重下降。治疗需长期使用多种抗生素以防止耐药。
9. Pulmonary Fibrosis | 肺纤维化
Pulmonary fibrosis is the formation of scar tissue in the alveolar walls. Causes include long-term exposure to asbestos or silica dust, certain drugs, autoimmune diseases and an unknown cause called idiopathic pulmonary fibrosis.
肺纤维化是肺泡壁形成瘢痕组织。病因包括长期接触石棉或二氧化硅粉尘、某些药物、自身免疫病，以及原因不明的特发性肺纤维化。
Fibrous tissue is thick, stiff and less elastic than normal lung tissue. This increases the diffusion distance for oxygen and carbon dioxide and reduces lung compliance, making the lungs harder to expand.
纤维组织比正常肺组织厚、僵硬且缺乏弹性。这增加了氧和二氧化碳的扩散距离，并降低肺顺应性，使肺部更难扩张。
The main symptoms are a dry cough and progressive shortness of breath, especially during exercise. Spirometry typically shows a restrictive pattern: both FEV₁ and FVC are reduced, and the FEV₁/FVC ratio remains normal or may even increase.
主要症状为干咳和进行性呼吸困难，尤其运动时。肺量计通常显示限制性模式：FEV₁ 和 FVC 均降低，而 FEV₁/FVC 比值保持正常甚至升高。
10. Comparing Lung Diseases | 肺部疾病比较
The table below summarises the main lung diseases, their pathology, key symptoms and typical spirometry patterns.
下表总结了主要肺部疾病的病理、主要症状和典型肺量计模式。
| Condition 疾病 | Main pathology 主要病理 | Key symptoms 主要症状 | Spirometry 肺量计模式 |
|---|---|---|---|
| Chronic bronchitis 慢性支气管炎 | Mucus hypersecretion and airway inflammation 黏液分泌过多与气道炎症 | Chronic productive cough, wheeze 慢性咳痰、喘息 | Obstructive 阻塞型 |
| Emphysema 肺气肿 | Alveolar wall destruction and loss of elastin 肺泡壁破坏与弹性蛋白丢失 | Severe breathlessness, barrel chest 严重呼吸困难、桶状胸 | Obstructive 阻塞型 |
| Asthma 哮喘 | Reversible bronchoconstriction and inflammation 可逆性支气管收缩与炎症 | Wheezing, chest tightness 喘息、胸闷 | Obstructive, reversible 阻塞型，可逆 |
| Lung cancer 肺癌 | Malignant tumour from epithelial mutations 上皮突变形成的恶性肿瘤 | Persistent cough, haemoptysis, weight loss 持续咳嗽、咯血、体重下降 | Variable 不一定 |
| Tuberculosis 肺结核 | Bacterial infection, tubercles, tissue destruction 细菌感染、结核结节、组织破坏 | Cough, fever, night sweats, weight loss 咳嗽、发热、盗汗、体重下降 | Variable 不一定 |
| Pulmonary fibrosis 肺纤维化 | Scar tissue in alveolar walls 肺泡壁瘢痕组织 | Dry cough, breathlessness on exertion 干咳、活动时呼吸困难 | Restrictive 限制型 |
11. Prevention and Treatment | 预防与治疗
Prevention focuses on reducing exposure to risk factors. Avoiding smoking is the single most effective way to prevent COPD and lung cancer. Reducing occupational exposure to dust and irritants, ensuring good ventilation, and vaccinating against TB with the BCG vaccine are also important.
预防的重点是减少危险因素暴露。避免吸烟是预防 COPD 和肺癌最有效的方法。减少职业性粉尘和刺激物暴露、保证良好通风以及接种卡介苗预防结核也非常重要。
Treatment depends on the disease. Bronchodilators and anti-inflammatory corticosteroids are used in asthma and COPD.
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