Diverticulum

A diverticulum is an outpouching of a hollow or fluid-filled structure in the body. Depending on which layers of the wall of that structure are involved, diverticula are described as either true or false. In medicine the word usually implies a structure that is not normally present, whereas in embryology it is also used for some normal structures that arise from others, such as the thyroid diverticulum, which grows out of the tongue. The word comes from the Latin diverticulum, meaning a bypath or byway, an apt picture for a small side pocket that branches from the main channel of an organ.