The walls of bronchioles contain

Appeared in: UPUMS Nsg.Officer-2024

Explanation

Bronchioles are small airways in the lungs that branch off from the larger bronchi.
Their walls are characterized by a prominent layer of smooth muscle and an inner lining of respiratory epithelium.
Crucially, bronchioles lack cartilage. The absence of cartilage is the primary histological feature that distinguishes them from bronchi.
The smooth muscle allows the diameter of the bronchioles to be regulated, controlling airflow resistance and distribution within the lungs.

Option A: This option is incorrect because it includes cartilage. Cartilage is found in the walls of the trachea and bronchi, but not in bronchioles.
Option C: This option is incorrect because it includes cartilage and omits smooth muscle. Bronchioles lack cartilage but have a significant layer of smooth muscle.
Option D: This option is incorrect because it includes cartilage and omits the respiratory epithelium lining. All airways are lined with some form of epithelium.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Histology of the Lower Respiratory Tract as background academic context rather than a clinical decision trigger.
The prominent smooth muscle in bronchioles is clinically significant in conditions like asthma. During an asthma attack, this muscle contracts excessively (bronchospasm), narrowing the airways and causing difficulty in breathing.
Bronchodilator medications, such as albuterol, work by relaxing this smooth muscle, which opens up the airways and relieves asthma symptoms.
What if the question asked about bronchi instead of bronchioles? The correct answer would then be 'Cartilage, smooth muscle and respiratory epithelium', as bronchi require cartilage plates for structural support to prevent collapse during breathing.

How to Approach the Question

First, identify the key term in the question: 'bronchioles'.
Recall the basic structure of the respiratory tract, from the trachea down to the alveoli.
Focus on the key structural difference between bronchi and bronchioles. The defining feature is the presence or absence of cartilage.
Remember the mnemonic: Bronchi have cartilage; Bronchioles are smaller and lack cartilage but have significant smooth muscle.
Evaluate the options. Eliminate any option that includes 'cartilage' for bronchioles.
The remaining option will be the correct composition of a bronchiole's wall.

Concept Tested & Keywords

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E6 Histology Inderbir 11e p. 16-18

E6 Physiology Guyton 4SAE Part 2A p. 58-60

Practise the full UPUMS Nsg.Officer-2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.