Small intestine lining. Coloured scanning electron micrograph (SEM) of the lining of the small intestine showing microvilli (purple) and a goblet cell (orange). Microvilli are small projections from the surface of epithelial cells of the gut, which increase the surface area for absorption of nutrients from digested food. Goblet cells secrete mucus, which lubricates the intestinal tract and protects the cells from digestive enzymes. Magnification: x10,500 when printed 10cm wide.