Fissure (Latin fissura, Plural fissurae) is a groove, natural division, deep furrow, or cleft found in the brain, spinal cord, and liver; or an unnatural tract found most commonly in the anus. In dentistry, a fissure is a break in the tooth enamel.

Natural Fissure

Various types of fissure are:

• Auricular fissure: found in the temporal bone
• Fissure of Bichat: found below the corpus callosum in the cerebellum of the brain.
• Broca's fissure: found in the third left frontal fold of the brain.
• Burdach's fissure: connects the brain's insula and the inner surface of the operculum.
• Calcarine fissure: extends from the occipital of the cerebrum to the occipital fissure.
• Callosomarginal fissure: found in the mesial surface of the cerebrum.
• Central fissure or Ronaldo's fissure: separates the brain's frontal and parietal lobes.
• Clevenger's fissure: found in the inferior temporal lobe of the brain
• Collateral fissure: found in the inferior surface of the cerebrum.
• Henle's fissure: the connective tissue between the muscle fibers of the heart.
• Hippocampal fissure: a fissure that extends from the brain's corpus callosum to the tip of the temporal lobe.
• Horizontal or Transverse fissure: found between the cerebrum and the cerebellum. Transverse fissure is also found in the liver and lungs.
• Longitudinal fissure: found in the lower surface of the liver, also a fissure that separates the right and left hemispheres of the cerebrum.
• Occipitoparietal fissure: found between the occipital and parietal lobes of the brain.
• Palpebral fissure: separates the upper and lower eyelids.
• Portal fissure: found in the under-surface of the liver.
• Sphenoidal fissure: separates the wings and the body of the sphenoid bone.
• Fissure of Sylvius: separates the frontal and parietal lobes of the brain from the temporal lobe.
• Umbilical fissure: found in front of the liver.
• Wernicke's fissure: separates the brain's temporal and parietal lobes from the occipital lobe.
• Zygal fissure: found in the cerebrum.

Abnormal Fissure

Fissure can also mean unnatural tract or ulcer, most commonly found in the anus. One of the most common types of fissure is anal fissure.