In
biological morphology and
anatomy, a sulcus (
pl.: sulci) is a furrow or fissure (
Latinfissura,
pl.: fissurae). It may be a groove, natural division, deep furrow, elongated cleft, or tear in the surface of a limb or an organ, most notably on the surface of the
brain, but also in the
lungs, certain
muscles (including the
heart), as well as in
bones, and elsewhere. Many sulci are the product of a surface fold or junction, such as in the
gums, where they fold around the
neck of the tooth.
In the
brain, a sulcus is a groove formed in the stage of
gyrification by the folding of the
cortex. There are many sulci and
gyri formed. A larger than usual sulcus may instead be called a
fissure such as the
longitudinal fissure that separates the two
hemispheres.