The mandibular fossa is a curved depression of the skull’s temporal bone. There are two of such cavities, with one on each side of the skull, thus making the phrase “mandibular fossae” more appropriate. The mandibular fossa is so named because it is a depression found at the mandible, which is commonly known as the lower jaw. It is also called glenoid fossa due to its shallowness, or lack of depth.
Located at the base and sides of the skull, and consequently supporting the sides of the head and eyes, known as the temples, the temporal bone is superior, or physically placed above, the mandible. Part of it, on each side of the skull, combines with the mandible to form the temporomandibular joint (TMJ). To form the joint, a thin and oval plate composed of fibrous and cartilaginous tissue called the articular disk joins the temporal bone and the mandible.
The mandibular fossa in particular functions as the part of the temporal bone that attaches to the articular disk’s upper surface. Attached to the under surface of the articular disk is a projection of the lower jaw called the mandibular condyle, which is separated from the coronoid process in front by a concave feature referred to as the mandibular notch. Thus, the mandibular fossa is specifically responsible for uniting, or articulating, with the mandibular condyle and plays an essential part in joining the temporal bone with the lower jaw bone.
In its front, the mandibular fossa’s boundary is a rounded projection filled with cartilage called the articular tubercle, or eminentia articularis. The mandibular fossa’s rear boundary is the tymapanic part of the temporal bone. A curved bony feature, it separates the mandibular fossa from the external auditory meatus, or external acoustic meatus, which is better known as the ear canal. A fissure of the temporal bone called the petrotympanic fissure — also known as the Glaserian fissure or the squamotympanic fissure — splits the fossa in half.
As part of the TMJ, the mandibular fossa is indirectly involved with the two types of movement associated with the joint via the union between the temporal bone and lower jaw bone. The temporal bone forms part of the joint’s upper region, and it is involved in the wide opening of the jaw as it glides; this is referred to as translational movement. The mandible, forming part of the lower TMJ compartment, assists in the initial opening of the jaw — a type of movement referred to as rotational movement.