Golgi apparatus consists of a stack of sacs called cisternae. It modifies a number of cell products delivered to it, often enclosing them in vesicles to be secreted. such products include trypsinogen (from pancreatic acinar cells), insulin (from beta-cells of the islets of Langerhans) and mucin (from goblet cells in the trachea), the Golgi is also involved in lipid modification in cells of the ileum, and plays a part in the formation of lysosomes.