Disorders of the respiratory system

When the lungs go wrong

A lung that works well has a large and clean surface for gas exchange, and open tubes that carry the air. Anything that damages the surface, or narrows the tubes, makes breathing hard. This lesson covers three disorders.

Asthma

Asthma is a difficulty in breathing that causes wheezing. It is caused by the inflammation of the bronchi and the bronchioles. The inflamed tubes become narrow, so the air does not move freely, and a whistling sound is heard when the person breathes out.

Emphysema

Emphysema is a chronic disorder. The walls of the alveoli are damaged. Many small alveoli join into a few big air spaces, and the respiratory surface decreases. Less oxygen can cross, so the person has trouble even in quiet breathing.

A major cause is cigarette smoking.

Occupational respiratory disorders

Some industries, especially those that involve grinding or stone-breaking, make so much dust that the defence mechanism of the body cannot cope. Recall that the hairs and mucus of the nasal chamber catch dust.

If a worker is exposed for a long time, the lungs become inflamed. This leads to fibrosis, which is the growth of too much fibrous tissue. The fibrous tissue damages the lungs seriously.

Workers in such industries need to wear protective masks. Other books name particular diseases, such as silicosis from silica dust and asbestosis from asbestos dust.

The three at a glance

• Asthma. The bronchi and bronchioles are inflamed. Wheezing and difficulty in breathing follow.
• Emphysema. The walls of the alveoli are damaged. The respiratory surface becomes smaller.
• Occupational disorders. Dust damages the lung tissue. Inflammation and fibrosis follow.

You should find that the oxygen taken up falls in step with the surface that is lost. A healthy adult has about 130 square metres. This figure is beyond the textbook. Measurements on human lungs give 120 to 140 square metres, and older books quote about 70 square metres. The model is only a teaching tool, so the exact area does not matter for the idea.

Try it in Python

The program follows a person whose respiratory surface falls by a few per cent each year.

Practise with new numbers

Common mistakes

• Saying that emphysema is an inflammation of the bronchi. It is damage to the walls of the alveoli. The bronchi are inflamed in asthma.
• Calling emphysema an acute disorder. It is chronic.
• Forgetting that smoking is a major cause of emphysema.
• Saying that fibrosis is the loss of tissue. It is the growth of too much fibrous tissue.
• Thinking that asthma damages the alveoli. It inflames the bronchi and the bronchioles.

Remember these

• Asthma: wheezing and difficulty in breathing, from inflammation of the bronchi and the bronchioles.
• Emphysema: chronic, the alveolar walls are damaged, the respiratory surface is smaller, and cigarette smoking is a major cause.
• Occupational disorders: dust from grinding or stone-breaking, inflammation, then fibrosis. Workers need protective masks.

Check yourself

Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.

1. What is asthma, and what causes it?

2. What is damaged in emphysema?

3. Name a major cause of emphysema.

4. Why do some workers get lung damage from dust?

5. What should workers in a stone-breaking industry wear?

References

• NCERT (2023). Biology, Textbook for Class XI, chapter 14, Breathing and Exchange of Gases.
• Knudsen L., Hummel B., Wrede C., Zimmermann R., Perlman C. E. and Smith B. J. (2023). Acinar micromechanics in health and lung injury: what we have learned from quantitative morphology. Frontiers in Physiology, 14, 1142221. DOI 10.3389/fphys.2023.1142221 (the surface of the human blood-gas barrier).