Zygoma

The zygoma (also known as zygomatic bone or malar bone) is an important facial bone which 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 zygomatico-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, 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
• posteromedial border articulates with greater wing of sphenoid above and orbital surface of maxilla below and serves as attachment for masseter muscle

Processes

• frontal process articulates with the frontal bone above and greater wing of sphenoid posteriorly, and terminates at the frontozygomatic suture
• temporal process is directed backwards, has an oblique, serrated end articulating with the zygomatic process of temporal bone, forming the zygomatic arch at the temporozygomatic suture

Articulations

The zygoma articulates with the greater wing of sphenoid, orbital surface and lateral border of maxilla, zygomatic process of the temporal bone (completing the zygomatic arch), and 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 lateral palpebrae ligament from frontal process of zygoma is absent in 5-10% of skulls