Top: example of a mucosoid with cells (the plasma membrane is labelled in green) producing protective mucins (MUC5AC) labelled in red (the yellow is where the two labels overlap creating the mucus layer). Bottom: example of a mucosoid with cells (the plasma membrane is labelled in red and the nuclei in blue) showing one cells producing Pepsinogen (in green) the precursor of pepsin, the main digestive enzyme.