Zygomatic bone

The zygomatic bone (also known as zygoma or malar bone) is an important facial bone that forms the prominence of the cheek. It is roughly quadrangular in shape.

Gross anatomy

Zygoma has three surfaces, five borders, and two processes.

Surfaces

• anterolateral surface is convex, pierced at its orbital border by the zygomaticofacial foramen, through which the zygomaticofacial nerve and vessels pass

• temporal (posteromedial) surface articulates with the maxilla, its smooth concave posteriorly forms an incomplete wall of the infratemporal fossa

• orbital surface forms the anterolateral part of the orbital floor and bears the zygomatic-orbital foramina, openings of the canals leading to the zygomaticofacial and zygomaticotemporal foramina.

Borders

• orbital (anterosuperior) border forms the inferolateral circumference of the orbital margin

• maxillary (anteroinferior) border articulates with the maxilla, and tapers just above the infraorbital foramen; the zygomaticomaxillary suture joins the maxillary margin of the zygomatic bone and the zygomatic process of the maxilla

• temporal (posterosuperior) border is of sinuous shape, convex above and concave below, and continuous with the posterior border of the frontal process and upper border of the zygomatic arch, bears the zygomaticotemporal foramen

• posteromedial border articulates with the greater wing of the sphenoid above and the orbital surface of the maxilla below and serves as an attachment for masseter muscle

• there is also a posteroinferior border

Processes

The zygomatic bone has three processes:

• frontosphenoidal process: articulates with the frontal bone above and the greater wing of the sphenoid posteriorly, and terminates at the frontozygomatic suture

• temporal or zygomatic process: is directed backwards, has an oblique, serrated end articulating with the zygomatic process of the temporal bone, forming the zygomatic arch at the temporozygomatic suture

• maxillary process: extends medially and inferiorly forming the floor of the orbit

Articulations

The zygoma articulates with the greater wing of the sphenoid, orbital surface and lateral border of the maxilla, the zygomatic process of the temporal bone (completing the zygomatic arch), and the zygomatic process of the frontal bone

Attachments

• lateral surface attaches zygomaticus minor and major muscles

• posteroinferior border - masseter muscle

• tubercle of frontal process (of Whitnall) - lateral palpebrae ligament, a suspensory ligament and part of the aponeurosis of levator palpebrae superioris

• maxillary border gives origin to part of levator labii superioris

Ossification

The zygoma ossifies from one center, appearing in fibrous tissue around the eighth week of life. Sometimes it may be divided by a horizontal suture into a larger upper and small lower division.

Variants

• the zygomaticofacial foramen can often be double or sometimes be absent

• the tubercle attaching the lateral palpebrae ligament from the frontal process of the zygoma is absent in 5-10% of skulls