Diagram of GI wall to show various kinds of glands -- some within the wall and some without (like the liver). These glands have ducts that empty into the lumen of the gut. In all cases, the epithelium lining the ducts and glands is continuous with the epithelium lining the lumen (cavity) of the gut. (Note: the test-tube-like glands, labeled "crypts of Lieberkuhn" here, are the same kind as the intestinal glands you saw under the microscope in the appendix in lab.)