ELECTRON MICROSCOPY: GASTROINTESTINAL: GI: COLON: Colonic gland (crypt of Lieberkuhn). (EM-labeled); RCH/P&SC9, transverse section of one crypt showing release of secretion (mucus) from a goblet cell into the lumen of the crypt. 1-15-absorptive epithelial cells, L-lumen of crypt, G-goblet cell