Cilia and stereocilia are similar filament-like structures projecting from the apical cell surfaces.  Cilia beat in rhythmic motions to propel substances across the apical surfaces of cells.  In this way, cilia act as an important cleansing mechanism for the respiratory tract.  In the female reproductive tract, cilia also play a role in directing released eggs into the fallopian tubes and moving these to the uterus.  Note that stereocilia are longer and not uniform in length.  They also do not beat like cilia.  These structures appear to have nutritive/supportive roles in the male reproductive tract or sensory functions in the special senses.

Microvilli

In contrast to cilia and stereocilia, microvilli are uniform folds of the membrane on the apical cell surfaces.  This repeated folding increases surface area for more efficient absorption, secretion, or excretion.  Microvilli form the "brush border" of the small intestine where most absorption in our bodies occurs.  Microvilli are also found on some kidney tubule cells and on osteoclasts, a cell involved in bone resorption.

Let's see cilia and microvilli!