In anatomy, grooves (also called sulci, especially in the brain) are linear depressions or furrows on the surface of an organ or bone. Brain: The cerebral cortex has prominent grooves called sulci* that increase its surface area. The ridges between sulci are called gyri. Bones: Many bones have grooves that accommodate blood vessels, nerves, or tendons. For example, the humerus bone in the arm has a groove for the radial nerve*. Teeth: The chewing surfaces of teeth have grooves that help in grinding food.