Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:
- a vertical portion, the squama frontalis, corresponding with the region of the forehead.
- an orbital or horizontal portion, the pars orbitalis, which enters into the formation of the roofs of the orbital and nasal cavities.
Borders
The border of the squama frontalis is thick, strongly serrated, bevelled at the expense of the inner table above, where it rests upon the parietal bones, and at the expense of the outer table on either side, where it receives the lateral pressure of those bones; this border is continued below into a triangular, rough surface, which articulates with the great wing of the sphenoid. The posterior borders of the orbital plates are thin and serrated, and articulate with the small wings of the sphenoid.
Structure
The squama and the zygomatic processes are very thick, consisting of diploic tissue contained between two compact laminæ; the diploic tissue is absent in the regions occupied by the frontal air sinuses.
The orbital portion is thin, translucent, and composed entirely of compact bone; hence the facility with which instruments can penetrate the cranium through this part of the orbit; when the frontal sinuses are exceptionally large they may extend backward for a considerable distance into the orbital portion, which in such cases also consists of only two tables.
Additional images
See also
External links
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 As such, some of the information contained herein may be outdated.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.
The Bones which form the Orbit |
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![The seven orbital bones of the skull](/2009-wikipedia_en_wp1-0.7_2009-05/I/250px_Orbital_bones.png) |
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Bones of head and neck: the cranium of the skull |
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Occipital |
Squama
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external (Inion/External occipital protuberance, Nuchal lines) - planes (Occipital, Nuchal) - internal (Cruciform eminence, Internal occipital protuberance, Sagittal sulcus, Internal occipital crest)
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Lateral parts
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Condyle (Condyloid fossa, Condylar canal) - Hypoglossal canal - jugular (Jugular process, Jugular tubercle)
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Basilar part
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Pharyngeal tubercle
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Other
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Foramen magnum
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Parietal |
Parietal eminence - Temporal line - Parietal foramen
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Frontal |
Squama
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Frontal suture - Frontal eminence - external (Superciliary arches, Glabella) - foramina (Supraorbital, Cecum) - Zygomatic process - internal (Sagittal sulcus, Frontal crest)
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Orbital part
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Ethmoidal notch - Lacrimal fossa - Trochlear fovea - Frontal sinus - Frontonasal duct
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Temporal |
Squama
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Articular tubercle - Suprameatal triangle - Mandibular fossa - Petrotympanic fissure - Zygomatic process
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Mastoid part
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Mastoid foramen - Mastoid process (Mastoid cells) - Mastoid notch - Occipital groove - Sigmoid sulcus - Mastoid antrum (Entrance)
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Petrous part
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Carotid canal - Facial canal (Hiatus) - Internal auditory meatus - Aqueduct of cochlea - Stylomastoid foramen
fossae (Subarcuate fossa, Jugular fossa) - canaliculi (Inferior tympanic, Mastoid) - Styloid process - Petrosquamous suture
(note: ossicles in petrous part, but not part of temporal bone)
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Tympanic part
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Suprameatal spine
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Sphenoid |
Surfaces
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Superior surface: Sella turcica (Dorsum sellae, Tuberculum sellae, Hypophysial fossa, Posterior clinoid processes) - Ethmoidal spine - Chiasmatic groove - Middle clinoid process - Petrosal process - Clivus
Lateral surface: Carotid groove - Sphenoidal lingula
Anterior surface: Sphenoidal sinuses
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Great wings
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foramina (Rotundum, Ovale, Vesalii, Spinosum) - Spine - Infratemporal crest - Sulcus for auditory tube
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Small wings
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Superior orbital fissure - Anterior clinoid process - Optic canal
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Pterygoid processes
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fossae (Pterygoid, Scaphoid) - pterygoid plates (Lateral, Medial) - Pterygoid canal - Hamulus
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Other
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Body - Sphenoidal conchae
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Ethmoid |
Plates
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Cribriform plate (Crista galli, Olfactory foramina) - Perpendicular plate
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Surfaces
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Lateral surface Orbital lamina - Uncinate process
Medial surface Superior nasal concha - Superior meatus - Middle nasal concha - Middle meatus
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Labyrinth
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Ethmoid sinus - ethmoidal foramina (Posterior, Anterior)
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