Illustration of a section through the wall of the duodenum, the first part of the small intestine showing Brunners glands (blue, bottom). These glands are found throughout the lining of the duodenum. They secrete an alkaline mucus that protects the duodenum from stomach acids passed into it with food from the stomach, lubricates the intestinal walls and provides an alkaline environment for intestinal enzymes. From Traite dAnatomie Humaine (1905) by French anatomist Leo Testut (1849-1925).