How is the structure of the lung adapted for respiratory function?

The lung can be divided into different sections regarding its function. The tube that connects the airway to the lungs is called the trachea, which is made of cartilage rings. These are flexible, and allow smooth transition of air. They are adapted by having tiny cilia, which are like tiny hairs that trap dust and woft it upward the respiratory tract, preventing dust entering the lungs. The trachea links to bronchi, tubes that connect the trachea to the lobes of the lungs, of which humans have 2 lobes, one on each side. Bronchi spread out and the diameter of the tubes decrease, creating structures called bronchioles. Bronchioles end in alveoli. Alveoli are highly folded sacs covered in blood capillaries that allow fast diffusion of gases, adapted as the folds increase surface area and they have a very thin membrane for rapid diffusion.