Fissure

In anatomy, a fissure (Latin "fissura", plural "fissurae") is a groove, natural division, deep furrow, elongated cleft, or tear in various parts of the body. It is also generally called a sulcus, but this term can also reffer specifically to the analagous brain structure.
Abnormal fissure.
Fissure can also refer to an unnatural tract or ulcer, most commonly found in the anus and called an anal fissure.