Describe the arrangement of terminal airways
Terminal bronchioles branch into respiratory which have a transitional role and are identical to terminal bronchioles except the smooth muscle is discontinuous and they have alveoli in their walls. Alveolar ducts have an increased number of alveoli in their walls and communicate with alveolar sacs. They have no smooth muscle and are supported by elastic. Several alveoli can be associated with an alveolar sac. It is lined by simple squamous epithelium and has no smooth muscle.