Which statement about the trachea is accurate?

• A. It runs down the anterior wall and is composed of cartilage rings throughout.
• B. It is a thick-walled tube with smooth muscle throughout.
• C. It is comprised mainly of skeletal muscle.
• D. It runs down the posterior wall and is composed of smooth muscle.

Answer: (D)

The key idea is the different composition of the trachea’s walls. The trachea is supported by C-shaped rings of hyaline cartilage on the front and sides, which keep the airway open, while the back wall is a flexible, smooth-muscle membrane called the trachealis. This posterior smooth muscle allows slight constriction and plays a role in coughing. The trachea itself runs in front of the esophagus, not along its posterior wall, and it isn’t made up mainly of skeletal muscle or entirely smooth muscle. So the statement that the posterior wall is smooth muscle best reflects the trachea’s structural arrangement.