Find each of these structures on your slide 46, using the following photos as a guide. The larger bronchioles are lined with an epithelium that is pseudostratified columnar with or without cilia. However, the Goblet cells are no longer present. Also, there are no more cartilage plates. As the bronchioles become smaller, the epithelium becomes cuboidal.
Most bronchioles show a pronounced smooth muscle coat.
In this slide, the smooth muscle is red, embedded in green connective tissue. The bronchioles are also accompanied by pulmonary arteries, seen in the photograph to the left. Note that the bronchiole is easily distinguished from the thin walled alveoli. As you study these sections, you can appreciate the extent of the capillary bed in the lung. All blood vessels are filled with red blood cells, which delineate the capillary spaces.