Defining a Sulcus
A sulcus, derived from the Latin word for “furrow,” is an anatomical term describing a groove on a surface. This term is broadly used in anatomy. Its plural form is sulci. While a sulcus refers to a shallow groove, a deeper indentation is often called a fissure.
Sulci in the Human Brain
The cerebral cortex, the brain’s outer surface, has a complex, wrinkled appearance due to its folds. These folds consist of elevated ridges (gyri) and the grooves between them (sulci). These shallow grooves surround gyri, contributing to the brain’s unique folded structure.
These grooves divide the brain’s surface into distinct lobes and regions. For example, the central sulcus separates the frontal lobe from the parietal lobe. It also marks the boundary between the primary motor cortex and the primary somatosensory cortex. The lateral sulcus separates the temporal lobe from the frontal and parietal lobes. The parieto-occipital sulcus further divides the parietal and occipital lobes.
The Role of Sulci in Brain Function
The presence of sulci significantly increases the surface area of the cerebral cortex. This intricate folding allows a much greater amount of neural tissue, including neurons and their connections, to be packed within the confined space of the skull. This expanded surface area is directly associated with the brain’s capacity for higher cognitive functions such as thinking, language, memory, and reasoning.
Specific sulci also function as anatomical landmarks defining functional areas of the brain. Research suggests that the morphology of sulci, such as their width, can correlate with cognitive performance. For instance, some studies indicate that a wider sulcal span in certain brain regions may be associated with diminished cognitive abilities, particularly processing speed, in older individuals.
Sulci in Other Body Parts
The term “sulcus” is a general anatomical descriptor, and while most commonly associated with the brain, it describes grooves in various other body parts. These non-brain sulci serve diverse functions, often accommodating structures or marking divisions.
An example is the intertubercular sulcus, found on the humerus. This groove, located between two bony projections, provides a pathway for the biceps muscle tendon. Another instance is the coronary sulcus, a groove on the surface of the heart that encircles it, separating the atria from the ventricles. This sulcus also contains important blood vessels that supply the heart muscle.