Illustrated Encyclopedia of Human Anatomic Variation: Opus V: Skeletal Systems: Cranium
Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed
The foramina of the zygomatic bone that transmit branches of the zygomatic nerve are often subject to variation in number and position.
A bipartite zygomatic (os japonicum or os ainoicum) has frequently been observed. The incidence in Japanese is 7%, hence the name, and in other ethnic groups 2.5-6.5%.
A zygomatic bone may also be tripartite, possessing extra sutures and accessory bones.
An orbital tubercle, in the orbital surface of the zygomatic bone and inferior to the frontozygomatic suture, provides an attachment site for the lacertus of the lateral rectus muscle (about 90% of cases - 89.12% of 285 skulls) (Whitnall). It was more developed in males than in females; no racial differences.
The zygomatic bone may or may not, with equal frequency, participate in forming the inferior orbital fissure.
A processus marginalis is found arising from the posterior edge of the facies lateralis in about 50% of skulls, and may serve as the insertion to part of the temporal fascia.
The opening of the zygomaticotemporal and zygomaticofacial canals may be increased in number.
Numerous cases have been reported in which the zygomatic bone does not contribute to the formation of the inferior orbital fissure as a result of the articulation of the greater wing of the sphenoid with the maxilla, or by the intervention of a wormian bone. The maxilla may be directly joined to the zygomatic process of the temporal bone by a dorsal extension of the zygomatic process of the maxilla. The maxillary process may articulate with the lacrimal hamulus.
Bipartite Os Zygomaticum.
Supernumerary Bones of the Zygomatic Arch.
Bipartite Os Zygomaticum
References
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DiDio, L.J.A. (1942) Observações sobre o "tuberculo orbitario" de Whitnall no ossa zigomético do Homem (compesquisas no vivo). Ann. Fac. Med. Univ. São Paulo 18:43-69.
DiDio, L.J.A. (1962) The presence of the eminentia orbitalis in the os zygomaticum of Hindu skulls. Anat. Rec. 142:31-39.
Gruber, W. (1873) Über den an der Schläfenfläche des Jochbeines gelagerten Kiefer-Schläfenbogen - Arcus maxillo-temporalis intra-juglais - beim Menschen; nebst Nachträgen zum zweigetheilten Jochbeine - Os zygomaticum bipartitum - ohne oder mit Vorkommen des Kiefer-Schläfenbogens. Arch. Anat. Physiol. Wissen. Med. 1873:208-240.
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Gruber, W. (1876) Ein Nachtrag zum Vorkommen des zweigetheilten Jochbeines - Os zygomaticum bipartitum -, bei Anwesenheit des Kiefer-Schläfenbogens - Arcus maxillo-temporalis intrajugalis. Arch. Anat. Physiol. Wissen. Med. 1876:230-235.
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Marro, G. (1907) Contribution à la casuistique et la interprétation des anomalies de l'arcade zygomatique. Arch. Ital. Biol. 47:476-477.
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Nicola, B. (1903) Sur la suture zygomatico-frontalis. Arch. Ital. Biol. 40:313-314.
Nicola, B. (1905) Sur la suture zygomatico-frontalis. Arch. Ital. Biol. 43:315-316.
Nicola, B. (1907) Division verticale totale de l'os zygomaticum. Arch. Ital. Biol. 47:478.
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