This low mag EM shows three columnar ciliated cells. The dark staining structures at the base of the cilia are the basal bodies in the apical cytoplasm. Among the cilia, microvilli can be seen. The basement membrane is located at the bottom of this image. The cytoplasm of each cell contains a nucleus and many mitochondria which supply energy for the movement of the cilia. Apical modifications such as cilia, microvilli and stereocilia (long microvilli) are found on simple and pseudostratified epithelia but not on stratified epithelia (HA13-HA15), which function mainly as barriers.