Disorders of the respiratory system

Disorders of the respiratory system

In plain words: breathing well needs open airways, a huge surface of thin alveolar walls, and lung tissue that is soft and stretchy. Asthma narrows the airways, emphysema destroys the alveolar walls, and inhaled hazardous dust can inflame and scar lung tissue.

Asthma

Asthma is a difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles.

NCERT Biology (Class 11), Section 14.6, page 190

• The problem is in the conducting airways: the bronchi and bronchioles are inflamed (page 190).
• Wheezing is “a whistling sound when you breathe out” (beyond the NCERT text; the US National Heart, Lung, and Blood Institute, “Asthma: Symptoms”, public domain).

Emphysema

Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased.

NCERT Biology (Class 11), Section 14.6, page 190

• The problem is in the exchange part: with the alveolar walls damaged, there is less surface for the diffusion of O_₂ and CO_₂ (page 190).
• One of the major causes is cigarette smoking (page 190).

Occupational respiratory disorders

• In certain industries, especially those involving grinding or stone-breaking, so much dust is produced that the body’s defence mechanism cannot fully cope (NCERT page 191).
• Long exposure can cause inflammation leading to fibrosis, the proliferation of fibrous tissue, and so serious lung damage (page 191).
• NCERT advises protective masks (page 191). Beyond NCERT, effective prevention first controls dust at its source with methods such as wet cutting and extraction; where respiratory protection is needed, it must be an appropriate, correctly fitted respirator. An ordinary loose mask does not reliably prevent harmful dust exposure (CDC/NIOSH, “Safe Work Practices” and “A Guide to Respirators Used for Dust in Construction”).

Beyond the NCERT text, two well-known examples:

• Silicosis is “a lung disease caused by inhaling excessive amounts of respirable crystalline silica”. Cutting, grinding, polishing and drilling can raise such dust, as in stonecutting and quarry work. Silicosis is not reversible, but it is preventable (CDC, National Institute for Occupational Safety and Health, “Silica and Worker Health”).
• Asbestosis is “a diffuse interstitial fibrosis of lung tissue resulting from inhalation of asbestos fibers”, and the fibrosis can progress even after exposure ends (Agency for Toxic Substances and Disease Registry, ATSDR, “Asbestos Toxicity”).

(NCERT pages 190–191.)

Solved examples

Common mistakes to avoid

Quick revision summary

• Asthma: difficulty in breathing with wheezing, from inflammation of the bronchi and bronchioles.
• Emphysema: a chronic disorder in which alveolar walls are damaged and the respiratory surface decreases; cigarette smoking is a major cause.
• Occupational respiratory disorders: dust from grinding or stone-breaking causes inflammation and fibrosis; prevention uses dust controls and suitable fitted respiratory protection when required.

Questions students ask

Is asthma the same as emphysema, and can asthma lead to emphysema?

Asthma is not the same as emphysema: asthma inflames the airways, the bronchi and bronchioles, while emphysema is a chronic disorder that damages the alveolar walls and so reduces the respiratory surface (NCERT page 190). In asthma the airways become inflamed and narrowed at times (NHLBI, “Asthma”), whereas emphysema causes lasting alveolar damage and can worsen over time (MedlinePlus, “COPD”); treatment can control asthma and help manage COPD symptoms and progression, although neither currently has a cure (NHLBI, “Asthma” and “COPD”). Beyond the NCERT text, asthma does not usually turn into emphysema: people with asthma have a higher risk of COPD, the group of diseases that includes emphysema, but most people with asthma will not get it (MedlinePlus, “COPD”).

Is emphysema the same as COPD?

Emphysema is one type of COPD, not another name for it: COPD, chronic obstructive pulmonary disease, is a group of lung diseases that make it hard to breathe and get worse over time, and its two main types are emphysema and chronic bronchitis (MedlinePlus, “COPD”). In emphysema the walls between many of the air sacs are damaged (NHLBI, “COPD”), as in NCERT’s damaged alveolar walls (NCERT page 190), while in chronic bronchitis the lining of the airways is repeatedly irritated and inflamed (NHLBI, “COPD”). The term COPD is beyond the NCERT text, which names asthma, emphysema and occupational disorders.

Why does cigarette smoking cause emphysema?

Cigarette smoking causes emphysema because smoke breathed in over many years damages the lungs: the walls between many air sacs are destroyed and the air sacs lose their elastic quality (NHLBI, “COPD: Causes and Risk Factors”). NCERT names cigarette smoking as one of the major causes of emphysema, the disorder in which damaged alveolar walls decrease the respiratory surface (NCERT page 190). Beyond the NCERT text, smoking is the main risk factor for COPD, and long exposure to other lung irritants, such as air pollution, chemical fumes and dust at work, and smoke from cooking or heating fuels in unventilated homes, also raises the risk (same source).

Are silicosis and asbestosis in NCERT and the NEET syllabus?

Silicosis and asbestosis are not named in NCERT or in the NEET (UG) 2026 syllabus, whose list of disorders ends with “Occupational respiratory disorders”, but they are two well-known examples of that group. Both are pneumoconioses, lung diseases caused by the lung’s reaction to breathing in certain dusts: silicosis comes from silica dust and asbestosis from asbestos fibres (CDC, NIOSH, “Pneumoconioses”). They fit NCERT’s account of industrial dust that, over long exposure, causes inflammation and then fibrosis (NCERT page 191); they cannot be cured but can be prevented by controlling the dust (CDC, NIOSH, as above), and NCERT advises protective masks, with the practical respirator/source-control distinction explained above.

Practice questions

Try each question first, then open the answer to check your working.

1. Q1. What is one of the major causes of emphysema?

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   Cigarette smoking (NCERT page 190).

2. Q2. What is fibrosis?

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   The proliferation of fibrous tissue, which seriously damages the lungs (NCERT page 191).

3. Q3. Inflammation of which structures causes asthma?

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   The bronchi and bronchioles (NCERT page 190).