sphenoid bone


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Related to sphenoid bone: palatine bone

sphenoid bone

n.
A compound bone with winglike processes, situated at the base of the skull.

sphe·noid bone

(sfē'noyd bōn)
A bone of irregular shape occupying the base of the skull; it is described as consisting of a central portion, or body, and six processes: two greater wings, two lesser wings, and two pterygoid processes; it articulates with the occipital, frontal, ethmoid, and vomer, and with the paired temporal, parietal, zygomatic, palatine, and sphenoidal concha bones.
Synonym(s): sphenoid (2) .

sphenoid bone

The wedge-shaped, bat-like central bone of the base of the skull.

orbit 

A rigid bony cavity in the skull which contains an eyeball, orbital fat, the extraocular muscles, the optic nerve, nerves and blood vessels, lacrimal system and fibrous tissue of various kinds. This packing serves to keep the eyeball reasonably well fixed in place as it rotates. The orbital cavity has the approximate form of a pyramid. The walls of the orbital cavity are formed by seven bones. The medial wall of the orbit consists of: (1) the frontal process of the maxilla (maxillary); (2) the lacrimal bone; (3) the lamina papyracea of the ethmoid; and (4) a small part of the body of the sphenoid. The floor of the orbit consists of: (1) the orbital plate of the maxilla; (2) the orbital surface of the zygomatic (malar) bone and (3) the orbital process of the palatine bone. The lateral wall of the orbit consists of (1) the orbital surface of the greater wing of the sphenoid, and (2) the orbital surface of the zygomatic. The roof of the orbit is made up mainly by the frontal bone and behind this by the lesser wing of the sphenoid. The orbit is lined with a membrane of tissue called the periorbita (or orbital periosteum) which extends to the orbital margin (anterior rim of the orbit) where it becomes continuous with the periosteum covering the facial bones. The periorbita is loosely attached to the bones except at sutures, foramina and the orbital margin where it is firmly attached. The bones are much thicker at the margin (rim) than they are along the walls of the orbital cavity. There are many apertures and gaps in the orbit through which blood vessels and nerves pass (see Table O4). See orbital axis; optic canal; inferior orbital fissure; superior orbital fissure; orbital fracture; cavernous haemangioma; lamina papyracea.
Table O3 Bones forming the walls of the orbit
roofmedial wall
1. frontal1. maxilla
2. lesser wing of sphenoid2. lacrimal
3. ethmoid
4. sphenoid
floorlateral wall
1. maxilla1. greater wing of sphenoid
2. zygomatic
3. palatine2. zygomatic

Table O4 Orbital apertures
aperturelocationcontents
optic canalat the apex (in lesser sphenoid)optic nerve
ophthalmic artery
sympathetic nerve fibres
superior orbital fissureat the apex (gap between greater and lesser sphenoid)III, IV, V, VI nerves
sympathetic nerve fibres
ophthalmic vein
recurrent lacrimal artery
inferior orbital fissurebetween lateral wall and posterior part of the floorinfraorbital nerve
zygomatic nerve
branch of inferior ophthalmic vein
nerve fibres from the
pterygopalatine (sphenopalatine)
ganglion to orbital periosteum
ethmoidal foramina (anterior and post.)medial wall (frontal/ethmoidal suture)ethmoidal vessels
ethmoidal nerve/external nasal nerve
zygomatic foramenlateral wallzygomatic nerve and vessels
nasolacrimal canalmedial wall (maxilla/lacrimal)nasolacrimal duct

sphe·noid bone

(sfē'noyd bōn)
A bone of irregular shape occupying the base of the skull.
Synonym(s): sphenoid (2) .
References in periodicals archive ?
The optic strut represents a bony formation that connects the body of sphenoid bone and its lesser wing.
Tumors invaded the greater wing of the sphenoid bone in one case, anterior clinoidal process in one case, olfactory groove or sphenoidal platinum in ten cases, cavernous sinus in two cases, and the third ventricle in eight cases.
When 3D imaging is required to visualise anatomic structures, such as processes of sphenoid bone, hard/soft palate, and oropharynx, CBCT should be preferred over a CT image.16 These images are an excellent aid to rule out skeletal pathology, but they cannot confirm a hamulus pain syndrome.
Giant cell tumor of the sphenoid bone. Skull Base Surg 1998;8(2):93-7.
It also articulates with the ethmoid bone, the lacrimal bones and the sphenoid bone. In addition, the frontal bone forms a large portion of the superior aspect of the orbit, articulating with the zygoma at the frontozygomatic suture to form the lateral aspects of the orbital walls.
On the other hand, lateral pterygoid muscle presents a superior fascicle originated in the horizontal part of the greater wing of sphenoid bone, including the infratemporal crest where it reach the sphenoidal tubercle (Rouviere & Delmas).
The optic strut represents a bony formation that connects the body of sphenoid bone and its lesser wing and separates optic canal from the medial part of the superior orbital fissure.
Isolated lesion of sphenoid bone is a rare entity,!6!
Then the surface area of each of the sixbony components--the perpendicular plate of the ethmoid bone, the vomer, the sphenoid bone, the nasal process of the frontal bone, the nasal bone, and the palatine crest--was measured with a transparent grid calibrated in square millimeters, Then we calculated the contributions that each of these bones made to the total osseous surface area and the contribution that the total bony component made to the total chondro-osseous septal surface area.
Aneurysmal bone cyst of sphenoid bone and clivus misdiagnosed as chordoma: a case report.
It was postulated that the mechanism of septal involvement was direct subperiosteal extension from the anterior portion of the sphenoid bone as described by Collins.