GENERAL HISTOLOGY

Detailed explanation-1: -Airway smooth muscle (ASM), an important tissue involved in the regulation of bronchomotor tone, exists in the trachea and in the bronchial tree up to the terminal bronchioles. The physiological relevance of ASM in healthy airways remains unclear.

Detailed explanation-2: -Phasic or tonic. Smooth muscle may contract phasically with rapid contraction and relaxation, or tonically with slow and sustained contraction. The reproductive, digestive, respiratory, and urinary tracts, skin, eye, and vasculature all contain this tonic muscle type.

Detailed explanation-3: -Smooth muscle fibers are located in walls of hollow visceral organs (such as the liver, pancreas, and intestines), except the heart, appear spindle-shaped, and are also under involuntary control.