Zygomatic bone

At a glance

English

Zygomatic bone

Latin (TA2)

Os zygomaticum

System

Bone

Region

Head

Side

Paired, left and right

About the zygomatic bone

The zygomatic bone, or cheekbone, is a paired irregular bone of the facial skeleton. It sits at the upper and outer part of the face, where it forms the point of the cheek and much of the bony rim around the outer and lower edge of the eye socket. Roughly diamond-shaped, it is braced against four neighbours: the frontal bone above, the greater wing of the sphenoid behind the orbit, the maxilla in front and below, and the temporal bone at the side.

Three of its corners run out as processes named after the bones they reach. The frontal process climbs to meet the frontal bone and forms the outer margin of the orbit. The temporal process points backwards and joins the temporal bone's zygomatic process to complete the zygomatic arch. The maxillary process runs forwards and down to the maxilla, contributing to the lower orbital rim. From the inner side, a thick orbital plate turns back into the socket and helps build its lateral wall and floor, meeting the sphenoid and maxilla; a short free edge between those contacts usually forms the front end of the inferior orbital fissure.

The bone has a convex outer face, a concave temporal face looking backwards and inwards, and an orbital face. Small foramina carry branches of the zygomatic nerve: the zygomaticofacial foramen opens on the cheek surface and the zygomaticotemporal foramen on the temporal surface. Its borders give attachment to soft tissues: the temporal fascia to the curved upper-posterior border, the masseter to the rough lower-posterior border, and the zygomaticus muscles to the outer face. A small orbital tubercle on the inner rim anchors the lateral palpebral ligament of the eyelids.

Because it projects, the cheekbone takes blows in falls, assaults and sports. A fracture commonly separates it at its sutures as a unit, flattening the cheek, disturbing the orbital floor and sometimes numbing the skin of the cheek. Ossification starts in membrane around the eighth fetal week, and the parts are united by about the fifth month.

Function and supply

Function

Acts as a strong buttress that carries chewing forces from the upper jaw up to the skull and back along the zygomatic arch, and gives origin to the masseter.

Nerve supply

Not innervated as a muscle is; the zygomatic nerve, from the maxillary division of the trigeminal, sends its zygomaticofacial and zygomaticotemporal branches through the bone to the skin of the cheek and temple.

Blood supply

Small branches accompany the zygomatic nerve branches through its foramina, and the transverse facial and infraorbital arteries supply the overlying tissues and periosteum.