Comissuras

Comissuras are anatomical connections that link corresponding structures on opposite sides of the body or organ, providing cross-communication and coordination between bilateral elements. In a broad sense, a commissure refers to a midline bridge through which neural or tissue fibers cross from one side to the other.

In the central nervous system, commissures are prominent pathways that enable interhemispheric communication and integration of sensory and motor information. The corpus callosum is the largest and most well known commissural tract, connecting the cerebral hemispheres to coordinate complex cognitive and motor functions. Additional cerebral commissures include the anterior commissure, which connects parts of the temporal lobes and carries a portion of the olfactory tract, and the posterior commissure, whose fibers influence the pretectal area and participate in aspects of the pupillary light reflex and visual processing.

The spinal cord also contains commissural elements. The anterior white commissure is a midline bundle where crossing fibers of the spinothalamic tract traverse to convey pain and temperature information to the opposite side of the body. In some references, a gray commissure is described as a midline connection within the gray matter that helps coordinate left-right activity of spinal neurons.

Outside the nervous system, the term is used for various tissue junctions at the body’s midline, such as labial commissures at the corners of the mouth (comissuras labiorum) and palpebral or canthal commissures at the corners of the eyelids (comissura palpebrarum). The word originates from Latin comissura, meaning “a bringing together.”

Comissuras vary across species and contexts, ranging from essential neural pathways to superficial anatomical landmarks.