Orbital part of frontal bone

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Orbital part of frontal bone
Frontal bone. Outer surface. (The Pars orbitalis is the bottom third.)
Frontal bone. Inner surface. (The Pars orbitalis is the bottom third.)
Latin pars orbitalis ossis frontalis
Gray's subject #33 137
Dorlands/Elsevier p_07/12617384

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


The orbital or horizontal part of the frontal bone (pars orbitalis) consists of two thin triangular plates, the orbital plates, which form the vaults of the orbits, and are separated from one another by a median gap, the ethmoidal notch.


  • In front of the ethmoidal notch, on either side of the frontal spine, are the openings of the frontal air sinuses.
    • These are two irregular cavities, which extend backward, upward, and lateralward for a variable distance between the two tables of the skull; they are separated from one another by a thin bony septum, which often deviates to one or other side, with the result that the sinuses are rarely symmetrical.
    • Absent at birth, they are usually fairly well-developed between the seventh and eighth years, but only reach their full size after puberty.
    • They vary in size in different persons, and are larger in men than in women.
    • They are lined by mucous membrane, and each communicates with the corresponding nasal cavity by means of a passage called the frontonasal duct.

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This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.