Simple columnar epithelium:
• It is composed of one layer of columnar cells (having one oval nucleus). They can be ciliated or non-ciliated.
• The non-ciliated, simple columnar epithelium contains microvilli on the apical surface of its cells. Microvilli increase the surface area of the epithelium, and thus, the non-ciliated type is found mainly lining the digestive tract and is involved in absorption of digested food products and in secretion of mucus, enzymes and other substances. It is also found lining the ducts of some glands.
• The ciliated simple columnar epithelium contains, of course, cilia on its apical surface. It is found in the small bronchi, the uterine tubes and part of the uterus. It is involved in the secretion of mucus and other substances and in moving mucus or female reproductive cells.