Small intestine lining. Light micrograph of a section through the finger-like projections (villi) of the duodenum, the uppermost part of the small intestine. These increase the surface area for the absorption of food. Within the columnar epithelium of the outer surface (purple) are goblet cells (light blue), which secrete mucus to lubricate food and prevent self-digestion. The lamina propria (central core, dark blue) contains the blood supply that transports the products of digestion. Magnification: x350 when printed at 10 centimetres wide.