A structure that forms a junction or bridge between two anatomical areas, especially in the two cerebral hemispheres or the halves of the spinal cord, is called commissures. It is located in various anatomical regions of the human body. 

Commissural neurons are the neuronal cells that can grow their axons all through the midline of the nervous system inside the brain and the spinal cord. 

In the cardiac anatomy of heart valves, the leaflet areas are the commissures. It could be the areas of temporal contact between the upper and lower eyelids. 

Commissures in mitral valve

The mitral valve is in the middle of the left ventricle and the left atrium. It is known as a bicuspid valve. 

• It comprises the papillary muscles, mitral annulus, chordae tendineae, anterior leaflet, and posterior leaflet. 
• These elements organise the valve apparatus that arrests the backflow of blood from the left ventricle to the left atrium at the systole.

Anterolateral commissure

• The anterior leaflet is positioned at the posterior region of the aortic root and is also bound. 
• The anterior leaflet is semicircular and has a free side without indentations. It is larger and denser compared to the posterior leaflet. 
• It has two sectors, including the rough zone and clear zone, disconnected by a ridge on the atrium.
• This ridge is situated from the corner of the anterior leaflet about a length of 1 cm. 
• During systole, the rough area of the anterior leaflet moves close to the posterior leaflet. 

Posteromedial Commissure

We can enumerate the posterior leaflets from anterolateral to posteromedial commissures, and these have indentations called scallops. 

The posterior leaflets consist of two-thirds of the annular border, and it has the name called ventricular or mural leaflets. These leaflets are present in the posterior region of the two commissural areas. 

• Unlike the anterior leaflet, the posterior leaflet divides into three parts or segments, including the basal, the rough, and the clear zones. 
• The rough zone is farthest to the ridge and wide at the scallops. 
• Like the anterior leaflet, the clear zone in the posterior leaflet has clear transillumination. The clear zone is in the middle of the basal and rough zone. 
• The basal zone exists only in the posterior leaflet and is present at the centre scallop in the middle of the mitral annulus and clear zone. 

Commissure eye

Canthus or palpebral commissure is the corner of the eye where there is a meeting of the upper and lower eyelids. These regions have two commissures, including a lateral palpebral commissure and a medial palpebral commissure.  

• The lateral palpebral commissure is more severe than the medial; here, the eyelids lie in close connection with the bulb of the eye.
• The medial palpebral commissure extends for a short distance about the nose, and the two eyelids dissociate by a triangular space called the lacus lacrimal. 

Cerebral commissure meaning

We can define cerebral commissures as the connection between the right and left cerebral hemispheres by three extents of fibres or axons. 

These commissures are transverse, and the nerve fibres clumps join the homologous areas of each hemisphere. They are known as the anterior commissure, the posterior commissure, and the corpus callosum.  

Anterior commissure 

It is a smaller bundle of nerve fibres that are conjugated parts of the temporal lobes. 

Posterior commissure

The posterior commissure is one of the fibre bundles that intersect, extending the pineal gland to link the midbrain areas of the cerebral hemispheres. 

Corpus callosum

The corpus callosum is the largest portion; we can call it the great cerebral commissure. It couples the considerable areas of the cerebral hemispheres, allowing the cerebral cortex to direct. 

The corpus callosum is the site for surgical dissection and commissurotomy to handle defined psychiatric disorders and epilepsy. 

Conclusion

Commissural systems are present all over vertebrate and invertebrate species. During the evolution of vertebrate organisms, numerous brain developmental events have been saved from lampreys to humans, possibly explaining the broad anatomical similarity of adult forebrain commissures all through the species. 

The body has various anatomical commissures, such as commissures in the mitral valve, eyelids, lips, spinal cord, and cerebral regions. Specifically, the corpus callosum commissure is the common greatest commissure of the hemisphere. 

We can conclude that cerebral commissure plays a vital role in the term of the commissure.