The glabella is a key anatomical landmark on the face, important for understanding facial expressions and relevant in cosmetic discussions.
Locating the Glabella
The glabella is the smooth skin area on the forehead, located between the eyebrows and directly above the nose. It corresponds to the underlying bony elevation connecting the two brow ridges. To locate it, place a finger at the center point between the eyebrows, just above where the bridge of the nose begins. This region is typically hairless, a characteristic from which its Latin name, glaber (meaning “smooth” or “hairless”), is derived. The glabella is considered a key landmark in craniofacial measurements, helping to assess facial proportions.
Underlying Structures and Function
Beneath the surface of the glabella lie several muscles that contribute to facial movements and expressions. The primary muscles in this area include the procerus and the corrugator supercilii. The procerus muscle is a small, pyramid-shaped muscle located centrally, pulling the skin between the eyebrows downwards. This action contributes to expressions like frowning.
The corrugator supercilii muscles are paired, small, and triangular, situated deep to the procerus and frontalis muscles. These muscles draw the eyebrows together and downward, creating vertical wrinkles above the glabella. Their contraction is associated with frowning or concentration. The motor nerve supply for these muscles comes from branches of the facial nerve. Sensory innervation to the skin over the glabella is provided by branches of the trigeminal nerve.
Common Appearances and Clinical Significance
The repeated contraction of the procerus and corrugator supercilii muscles in the glabella area frequently leads to the formation of visible lines. These lines are commonly known as “frown lines” or “eleven lines,” appearing as vertical creases between the eyebrows or horizontal lines across the bridge of the nose. Such lines become more pronounced over time due to persistent muscle activity.
Beyond its role in facial expressions and appearance, the glabella is significant in neurological assessments. The glabellar reflex, also known as the “glabellar tap sign,” is a primitive reflex elicited by repetitive tapping on the glabella. In a typical response, an individual blinks a few times initially but then suppresses further blinking, a process called habituation. However, if blinking persists with continued tapping, known as Myerson’s sign, it can indicate certain neurological conditions, such as Parkinson’s disease. This reflex is a tool in neurological examinations.