Identifying Smooth Muscle in Bronchus Histology

Steps:

• Recall bronchus structure: inner ciliated epithelium, submucosal glands, circular smooth muscle layer, and outer cartilage.
• Examine photomicrograph for layered tissues: look for dense, spindle-shaped cell bundles indicating involuntary muscle.
• Match labels to features: epithelium is columnar, cartilage is hyaline rings, glands are mucous/sebaceous.
• Confirm smooth muscle as the contractile ring controlling airway diameter, typically mid-wall.

Why C is correct:

• Label C shows bundles of elongated, nucleated cells without striations, matching the definition of smooth muscle as non-striated, involuntary tissue in bronchial walls.

Why the others are wrong:

• A identifies ciliated pseudostratified epithelium, the inner lining for mucociliary clearance.
• B marks hyaline cartilage rings, providing structural support.
• D points to submucosal glands, secreting mucus.

Final answer: C