Which structures are specialized for gas exchange in the lungs?

The structures specialized for gas exchange in the lungs are the alveoli. These tiny, balloon-like sacs are located at the end of the bronchial tubes and provide a vast surface area for the exchange of oxygen and carbon dioxide between the air and the bloodstream. The alveolar walls are extremely thin and are surrounded by a network of capillaries, allowing for efficient diffusion of gases. This is crucial for maintaining proper oxygen levels in the body and removing carbon dioxide, a waste product of metabolism.

The other structures listed serve different functions; the pleurae are membranes that surround the lungs and help reduce friction during breathing, the intercostal muscles are involved in the mechanics of breathing by facilitating chest expansion and contraction, and the trachea is the windpipe that conducts air to and from the lungs but is not involved in gas exchange. Thus, alveoli are the specific structures that facilitate this vital process.