Precentral Gyrus

ANATOMY AIIMS, GROSS ANATOMY, EMBRYOLOGY, NEUROANATOMY, MICROANATOMY, APPLIED/ CLINICAL ANATOMY

The Precentral Gyrus: A Key Player in Motor Control

The precentral gyrus, also known as the primary motor cortex, is a critical structure located in the frontal lobe of the cerebral cortex. Let’s delve into its anatomy, function, and significance.

Anatomy and Location

1. Position: The precentral gyrus lies on the surface of the posterior frontal lobe of the brain¹. It is situated in front of the postcentral gyrus and is mostly found on the lateral (convex) side of each cerebral hemisphere.
2. Borders:
   • Anterior Border: Represented by the precentral sulcus.
   • Inferior Border: Borders to the lateral sulcus (Sylvian fissure).
   • Medial Continuity: It is contiguous with the paracentral lobule.
3. Neurons:
   • The internal pyramidal layer (layer V) of the precentral cortex contains giant pyramidal neurons called Betz cells. These cells send long axons to the contralateral motor nuclei of the cranial nerves and to the lower motor neurons in the ventral horn of the spinal cord. These axons form the corticospinal tract.
   • Betz cells, along with their long axons, are referred to as upper motor neurons (UMN).

Function

1. Motor Control: The precentral gyrus is specialized for sending signals down to the spinal cord for movement¹.
2. Somatotopic Representation:
   • There is a precise somatotopic representation of different body parts in the primary motor cortex.
   • The leg area is located medially (close to the midline), while the head and face area are located laterally on the convex side of the cerebral hemisphere (cortical homunculus).
   • The arm and hand motor area is the largest and occupies the part of the precentral gyrus located between the leg and face area.

Blood Supply

• Branches of the middle cerebral artery provide most of the arterial blood supply for the primary motor cortex. The medial aspect (leg areas) is supplied by branches of the anterior cerebral artery.

Clinical Significance

Lesion- Paralysis of contra lateral side of the body.

In summary, the precentral gyrus plays a fundamental role in planning, executing, and controlling voluntary movements of the body. Its intricate neural architecture and precise organization contribute to our ability to move and interact with the world around.