Small intestine section. Light micrograph of a vertical section through the illeum, part of the small intestine. The upper layer (the digestive surface) consists of the fingerlike villi that increase the area of the intestine for absorption of digested food. The nutrients from the food pass into the blood capillary network under the villi. Below these are the muscular mucosa (red band) and the submucosa of blood vessels. The bottom half of the image consists of blocks of the circular and longitudinal muscles that line the outer surface of the intestines. Magnification: x100 when printed at 10 centimetres across.