The zygomatic bone is nearly quadrangular in shape and it features three surfaces, five borders and two processes. Besides forming the prominence of the cheek, the zygomatic bone also contributes to the formation of the zygomatic arch, the walls of the temporal and infratemporal fossae, and the floor and lateral wall of the bony orbit.
This article will discuss the anatomy and function of the zygomatic bone.
|Definition||A quadrangular bone of the skull that participates in the formation of the skeletal framework of the orbit and cheeks|
|Surfaces||Lateral, posteromedial, orbital|
|Borders||Anterosuperior, anteroinferior, posterosuperior, posteroinferior, posteromedial|
|Processes||Frontal process, temporal process, maxillary process|
|Foramina||Zygomaticotemporal foramen, zygomatico-orbital foramen|
|Joints||Zygomaticomaxillary suture, zygomaticofrontal suture, sphenozygomatic suture|
The zygomatic bone has three surfaces: lateral, posteromedial and orbital.
- The lateral (facial) surface faces towards the outside. It is smooth and convex, and it features a small opening called the zygomaticofacial foramen. This foramen transmits the zygomaticofacial nerve, artery and vein between the orbit and the face. The lateral surface also serves as the attachment area of the zygomaticus major muscle on its anterior half, and the zygomaticus minor muscle on its posterior half.
- The posteromedial (temporal) surface faces towards the temporal and infratemporal fossae. Its anteriormost portion is rough and serves for the articulation with the zygomatic (malar) process of maxilla via the zygomaticomaxillary suture. The posteromedial surface spreads over the medial side of the temporal process, comprising a part of the lateral wall of the infratemporal fossa. Near the base of the frontal process, the posteromedial surface features the zygomaticotemporal foramen which transmits the zygomaticotemporal nerve from the orbit to the temporal fossa.
- The orbital surface is smooth and concave. It faces towards the orbit and forms the anterolateral part of its floor and the anterior part of its lateral wall. It features the zygomatico-orbital foramen, which is a gateway to the bony canal found within the zygomatic bone. This canal branches into the zygomaticofacial and zygomaticotemporal canals, which open on the corresponding surfaces of the zygomatic bone (explained above). The former transmits the zygomaticofacial nerve and vessels, while the latter is traversed by the zygomaticotemporal nerve and vessels.
The zygomatic bone has five borders:
- The anterosuperior (orbital) border is concave and smooth. It is the border between the lateral and orbital surfaces of the zygomatic bone.
- The anteroinferior (maxillary) border is the articular surface for the zygomaticomaxillary suture. It also serves as an attachment site for the levator labii superioris muscle.
- The posterosuperior (temporal) border is continuous with the superior border of zygomatic arch and the posterior border of the frontal process. It serves as an attachment point for the temporal fascia.
- The posteroinferior border is rough and serves as the attachment site for the masseter muscle.
- The posteromedial border is serrated and articulates with the greater wing of sphenoid bone superiorly via the sphenozygomatic suture, and with the orbital surface of maxilla inferiorly. Between the articular surfaces, there is a small free surface of the posteromedial margin that comprises the lateral border of the inferior orbital fissure.
Temporal process of zygomatic bone
The temporal process originates from the lower half of the zygomatic bone. It is oriented posteriorly and slightly superiorly towards the temporal bone. The terminal tip of the temporal process is oblique and jagged and it articulates with the zygomatic process of temporal bone with which it comprises the zygomatic arch.
Frontal process of zygomatic bone
The frontal process originates from the upper margin of the zygomatic bone. It is oriented superiorly, comprising the lateral outline of the orbit. It articulates with the zygomatic process of frontal bone superiorly via the zygomaticofrontal suture, and with the greater wing of sphenoid bone posteriorly via the sphenozygomatic suture.
The frontal process features a bony tubercle on its orbital surface called the Whitnall’s tubercle, which serves as an attachment site for the lateral palpebral ligament, suspensory ligament of the eye, and the aponeurosis of levator palpebrae superioris muscle.
Maxillary process of zygomatic bone
The maxillary process arises from the anterosuperior angle of the zygomatic bone. It extends anteriorly, comprising the inferolateral margin of the orbit. The inferior margin of this process participates in the joint with the maxilla. Posteriorly, it is continuous with the orbital surface of the bone.
The second most common area of fracture in the face is the fracture of the zygomatic bone, especially of the left frontal process. This kind of injury often happens during a car accident or due to being punched in the face with a fist. Depending on the severity of the dislocation, the bone can either move slightly along its sutures or more severely in an anterior, medial, lateral or posterior direction.
Clinically, one should check for the following symptoms:
- A flattened cheek bone
- A subconjunctival hemorrhage
- None displacement and mobility
- A lowered lateral portion of the palpebral fissure due to the downward displacement of the lateral canthal ligament and ecchymosis.