Maximum amount of smooth muscle, in relation to wall thickness, is present in:
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.
Trachea
Bronchi
Terminal bronchioles
Respiratory bronchioles
Respiratory System Pa 1