Final answer:
In bronchial asthma, the bronchioles are obstructed due to inflammation, bronchospasm, and excessive mucus production, leading to difficulty in breathing.
Step-by-step explanation:
In bronchial asthma, the inflammation obstructs the bronchioles, which are the smaller air passages that branch off from the larger bronchi and lead to the alveoli in the lungs. These bronchioles become inflamed and constrict due to muscle contraction, swelling (edema), and excessive mucus production, making it difficult for air to enter the lungs. Immune system cells, including eosinophils and mononuclear cells, often infiltrate the bronchioles and contribute to the inflammation.