Yesterday in histology we started our study of epithelium. Here is a false color SEM image of tracheal epithelium. Notice the pseudostratified columnar ciliated epithelium. The green extensions are the cilia. The yellow bumps are microvilli present on the goblet cells. These cilia move mucus up the trachea in what is known as the mucus elevator. Smokers cough can be attributed in part to damaged cilia, thus mucus is left to accumulate in the trachea causing coughing with sputum.