Gall bladder. Coloured scanning electron micrograph (SEM) of the surface of a gall bladder. This mucosa lining is made up of cuboidal epithelial cells (yellow). Each cell of the gall bladder lining has microvilli (tiny projections) that increase its surface area and aid water uptake. Connective tissue (pink) is seen below the epithelial lining where some of the cells have come away in the preparation. The gallbladder is a sac that concentrates and stores bile produced by the liver and releases it into the duodenum (small intestine), where it aids the digestion of fats. Magnification: x2400 when printed at 10 centimetres wide.