Color enhanced transmission electron micrograph showing section of ileum, goblet cell between columnar epithelial cells. Magnification 5000x Goblet cell, any of the specialized epithelial cells, such as those found in the mucous membrane of the stomach, intestines, and respiratory passages, that secrete mucus. The goblet cells distend with mucin before secretion and collapse to a goblet shape after secretion. Ileum, the third and lowest division of the small intestine, extending from the jejunum to the cecum.