Surface view of tracheal epithelium as seen by scanning electron microscopy (SEM). Some cells have both cilia and microvilli while others only have microvilli. They can be distinguished from one another because of the greater length of cilia versus that of microvilli.
Cilia (purple) - ~8 to 10 µm in length and 250 nm in diameter.
Microvilli (blue) - ~1 µm in length and 100 nm in diameter.
Several red blood cells (red) are seen on the surface of the epithelium.
The morphology of the underlying pseudostratified columnar cells is not visible.