3. simple columnar epithelium Description: Single layer of columnar cells with oval nuclei often have an apical border of microvilli Many contain goblet cells(mucus-secreting unicellular glands) Function: absorption of nutrients secretion of mucus enzymes Locations: digestive tract, etc3. simple columnar epithelium Description: Single layer of columnar cells with oval nuclei ; often have an apical border of microvilli; Many contain goblet cells (mucus-secreting unicellular glands). Function: absorption of nutrients; secretion of mucus & enzymes. Locations: digestive tract,etc