The mandible, commonly known as the lower jawbone, is a prominent and movable bone in the human skull. It forms the lower part of the facial skeleton, providing structure to the chin and housing the lower teeth. Located inferior to the maxilla, or upper jaw, it is the largest and strongest bone of the facial skeleton. This bone is unique in the skull as it is the only one capable of significant movement, aside from the tiny bones within the middle ear.
The Mandible’s Bone Classification
The mandible is classified as an irregular bone, a category for bones with complex, non-uniform shapes that do not fit into the typical classifications of long, short, or flat bones. Irregular bones often have multiple projections, ridges, or other features that enable specialized functions, such as articulating with other bones, providing muscle attachment sites, or protecting internal organs. This classification reflects the mandible’s intricate form, which includes a curved body and two vertical extensions with various processes.
While primarily considered irregular, the mandible also exhibits characteristics of a flat bone due to its broad, somewhat flattened body. Flat bones are typically thin, often curved, and serve to protect internal organs or provide broad surfaces for muscle attachment. However, the mandible’s overall complexity, with its distinct U-shape, multiple processes for articulation, and muscle attachments, distinguishes it from a simple flat bone.
Unique Features of the Mandible’s Structure
The mandible’s distinctive structure features a horseshoe-shaped body, which forms the horizontal lower jaw and holds the lower teeth in place. Extending upwards from the posterior ends of the body are two vertical portions called rami. The junction where the body and rami meet is known as the angle of the mandible.
Each ramus terminates superiorly in two processes: the coronoid process and the condylar process. The coronoid process is an anterior, triangular projection that serves as an attachment point for chewing muscles like the temporalis. Posterior to this, the condylar process features a rounded head that articulates with the temporal bone of the skull, forming the temporomandibular joint (TMJ).
Primary Functions of the Mandible
The mandible plays a role in several oral functions, especially mastication, or chewing. Its mobility, facilitated by the temporomandibular joints, allows for diverse movements, including opening and closing the mouth, as well as side-to-side and forward-and-backward motions. These movements enable the precise grinding and tearing of food.
Beyond eating, the mandible aids speech articulation. Its controlled movements are important for forming various sounds and words. The mandible contributes to the overall structure and appearance of the lower face and chin. It provides support for the lower teeth and helps define facial contours.