View source for Orbital part of frontal bone

{{Infobox Anatomy |
  Name         = {{PAGENAME}} |
  Latin        = pars orbitalis ossis frontalis |
  GraySubject  = 33 |
  GrayPage     = 137 |
  Image        = Gray134.png |
  Caption      = Frontal bone. Outer surface. (The Pars orbitalis is the bottom third.) |
  Image2       = Gray135.png |
  Caption2     = Frontal bone. Inner surface. (The Pars orbitalis is the bottom third.) |
  System       = |
  MeshName     = |
  MeshNumber   = |
  DorlandsPre  = p_07 |
  DorlandsSuf  = 12617384  |
}}
{{CMG}}
__NOTOC__


==Overview==

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]].

=== Surfaces ===
* The '''inferior surface''' of each orbital plate is smooth and concave, and presents, laterally, under cover of the [[Zygomatic process of frontal bone|zygomatic process]], a shallow depression, the [[lacrimal fossa]], for the [[lacrimal gland]]; near the nasal part is a depression, the [[fovea trochlearis]], or occasionally a small trochlear spine, for the attachment of the cartilaginous pulley of the [[obliquus oculi superior]]. 
* The '''superior surface''' is convex, and marked by depressions for the convolutions of the [[frontal lobes]] of the [[brain]], and faint grooves for the meningeal branches of the [[ethmoidal vessels]]. 
** The [[ethmoidal notch]] separates the two [[orbital plate]]s; it is quadrilateral, and filled, in the articulated skull, by the [[cribriform plate]] of the ethmoid. 
*** The margins of the notch present several half-cells which, when united with corresponding half-cells on the upper surface of the ethmoid, complete the [[ethmoidal air cells]]. 
** Two grooves cross these edges transversely; they are converted into the anterior and posterior ethmoidal canals by the [[ethmoid]], and open on the medial wall of the [[orbit]]. 
*** The [[anterior canal]] transmits the [[nasociliary nerve]] and [[anterior ethmoidal vessels]], 
*** the posterior, the posterior [[ethmoidal nerve]] and vessels. 

* 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]].

==Additional images==
<gallery>
 Image:Orbital_bones.png|The seven bones which articulate to form the orbit.
 Image:Gray192.png|Medial wall of left orbit.
</gallery>

==External links==
* {{SUNYAnatomyLabs|29|st|02|02}} (orbital plate)
* {{RocheLexicon|34256.000-1}}

{{Gray's}}
{{Cranium}}

[[Category:Eye]]
[[Category:Anatomy]]

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