Maximum amount of smooth muscle, in relation to wall thickness, is present in:: (A) Trachea, (B) Bronchi, (C) Terminal bronchioles, (D) Respiratory bronchioles
Answer is C. The trachea and upper respiratory passages (first 7 generations) have cailage & glands in their walls but little smooth muscle. They are lined by ciliated epithelium. Intermediate-sized and small-sized bronchi and bronchioles do not contain cailage. Cilia are present till respiratory bronchioles Terminal bronchioles have maximum amount of smooth muscle.