In this pdf-note, we will learn the structure of the sphenoid bone (os sphenoidale). It is located in the central part of the cranial base and is the bottom of the middle cranial fossa. The bone contains many different foramina and cnals, in which many blood vessels and nerves pass.

The sphenoid bone consists of several parts:

• Body of the sphenoid bone (corpus ossis sphenoidalis)

• Greater wing (ala major) – paired

  

• Lesser wing (ala minor) – paired

  

• Pterygoid process (processus pterygoideus) – paired

  

  There are 6 surfaces of the body of the sphenoid bone:

• Superior (cerebral) surface (facies superior)

• Posterior surface (facies posterior), which fuses with the basilar part of the occipital bone

• Anterior surface (facies anterior)

• Inferior surface (facies inferior)

• Lateral surface (facies lateralis) – paired

  Inside the body of the sphenoidal bone, there is a pneumatized cavity called sphenoidal sinus (sinus sphenoidalis). It is separated by a septum into left and right parts and communicates with the superior nasal meatus of the nasal cavity.

  

  On the superior surface of the body, there is a rather large recess called sella turcica (sella turica).

  

  The hypophysial fossa (fossa hypophysialis), which contains the endocrine gland called the pituitary gland, is located in the center of this sella.

  

  The sella turcica is delimited by the tuberculum sellae (tuberculum sellae) anteriorly, and by the dorsum sellae (dorsum sellae) posteriorly.

  

  

  Anteriorly to the tubercle of the sella, there is a prechiasmatic sulcus (sulcus prechiasmaticis). The optic chiasm lies posteriorly to it.

  

  From each side, the dorsum continues to the lateral side into the posterior clinoid process (processus clinoideus posterior).

  

  In addition, there is a recess on the flanks of the dorsum, in which the internal carotid artery passes. This is the carotid sulcus (sulcus caroticus).

  

  Closer inferiorly, the groove is slightly delimited by the socalled sphenoidal lingula (lingula sphenoidalis) on the outside.

  

  Sometimes, on the medial side of the carotid sulcus, there is a small middle clinoid process (processus clinoideus medius). However, this is more of an anatomical feature than a rule.

  On the anterior surface of the body, a sphenoidal crest (crista sphenoidalis) passes along the median line, which connects to the perpendicular plate of the ethmoidal bone.

  

  The crest expands inferiorly and forms a so-called sphenoidal rostrum (rostrum sphenoidale).

  

  Together with the wings of the vomer, it forms a vomerorostral canal (canalis vomerorostralis).

  On the flanks of the crest on each side there is a sphenoidal concha (concha sphenoidalis), which separates the opening of the sphenoidal sinus (aperture sinus sphenoidalis).

  

  

  The greater and lesser wings arise from the lateral surfaces of the body of the sphenoidal bone. Let’s learn more about them.

  There are three critical foramina on the base of the greater wing. In the top-down and anterior-posterior order, these are:

• Foramen rotundum (foramen rotundum), through which the maxillary nerve passes

  

• Foramen ovale (foramen ovale), through which the mandibular nerve passes

  

• Foramen spinosum (foramen spinosum), through which the middle meningeal artery and the meningeal branch of the mandibular nerve pass

  

  There may also be some irregular foramina in this region, which are individual anatomical features.

• These include the sphenoidal emissary foramen (foramen venosum), which contains the emissary vein.

• As well as the petrosal foramen (foramen petrosum), which contains the lesser petrosal nerve.

  The greater wing has 4 surfaces:

• Cerebral surface (facies cerebralis)

  

• Orbital surface (facies orbitalis)

  

• Maxillary surface (facies maxillaris)

  

• Temporal surface (facies temporalis)

  

  And 4 margins:

• Frontal margin (margo frontalis)

  

• Squamosal margin (margo squamosis)

  

• Zygomatic margin (margo zygomaticus)

  

• Parietal margin (margo parietalis)

  

  On the cerebral surface, there are traces of brain structures adherence:

• Impressions of cerebral gyri (impressiones digitatae)

• Juga cerebralia (juga cerebralia)

• Arterial grooves (sulci arteriosi)

  The orbital surface is part of the lateral wall of the orbit. There is an inferior orbital fissure (fissura orbitalis inferior) between the inferior margin of the orbital surface and the maxilla.

  

  The maxillary surface faces the pterygopalatine fossa and includes the foramen rotundum already mentioned.

  On the temporal surface, there is an infratemporal crest (crista infratemporalis), which separates it into superior and inferior parts.

  

  The inferior part is also called the infratemporal surface (facies infratemporalis).

  

  The spine of the sphenoidal bone (spina ossis sphenoidalis) arises inferiorly from the greater wing. The muscles and ligaments insert into this spine.

  

  Also, on the inferior part of the greater wing, there is a sulcus of the auditory tube (sulcus tubae auditivae), to which the cartilaginous part of the auditory tube is attached.

  

  The lesser wing of the sphenoidal bone has two surfaces:

• Superior surface (facies superior)

• Inferior surface (facies inferior)

  And two margins:

• Anterior margin (margo anterior)

• Posterior margin (margo posterior)

  The left and right wings are connected by jugum sphenoidale (jugum sphenoidale).

  

  The lesser wing has two bases that delimit the optic canal (canalis opticus). The optic nerve and the ophthalmic artery pass through this canal.

  

  An anterior clinoid process (processus clinoideus anterior), to which the dura mater is attached, arises posteriorly from each lesser wing.

  

  Between the lesser wing and the greater wing, the superior orbital fissure (fissura orbitalis superior) is located. The oculomotor nerve, trochlear nerve, abducent nerve, ophthalmic nerve, and superior ophthalmic vein pass through it.

  

  The pterygoid process arises inferiorly from the sphenoidal bone. It is formed by two plates:

• Medial plate (lamina medialis)

  

• Lateral plate (lamina lateralis), where the lateral pterygoid muscle arises.

  

They are separated by a pterygoid notch (incisura pterygoidea).

This process takes part in the formation of the nasal cavity and the infratemporal fossa.

There is a pterygoid fossa (fossa pterygoidea) on the posterior surface of the process between the plates.

The medial pterygoid muscle arises in this region. A bit cranially to the pterygoid fossa, there is another fossa called the scaphoid fossa (fossa scaphoidea).

On the posterior margin of the lateral plate, there is a small, pointed protrusion called pterygospinous process (processus pterygospinosus).

At the base of the pterygoid process, there is a foramen forming a pterygoid canal (canalis pterygoideus). The nerve and blood vessels of the pterygoid canal pass through it.

The pterygoid hamulus (hamulus pterygoideus) arises from the inferior part of the medial plate

It has a groove of the pterygoid hamulus (sulcus hamuli pterygoidei).

A bit medially to the medial plate of the pterygoid process, a small vaginal process (processus vaginalis) arises.

Two grooves adhere to it

• palatovaginal groove (sulcus palatovaginalis), which forms the canal of the same name together with the palatine bone

  

• vomerovaginal groove (sulcus vomerovaginalis), which forms the canal of the same name together with the vomer

Dictionary

Sphenoid bone

Sphenoid bone

os sphenoidale

Body of the sphenoid bone

corpus ossis sphenoidalis

Greater wing

ala major

Lesser wing

ala minor

Pterygoid process

processus pterygoideus

Superior surface

facies superior

Posterior surface

facies posterior

Anterior surface

facies anterior

Inferior surface

facies inferior

Lateral surface

facies lateralis

Sphenoidal sinus

sinus sphenoidalis

Sella turcica

sella turcica

Hypophysial fossa

fossa hypophysialis

Tuberculum sellae

tuberculum sellae

Dorsum sellae

dorsum sellae

Prechiasmatic sulcus

sulcus prechiasmaticus

Posterior clinoid process

processus clinoideus posterior

Carotid sulcus

sulcus caroticus

Sphenoidal lingula

lingula sphenoidalis

Middle clinoid process

processus clinoideus medius

Sphenoidal crest

crista sphenoidalis

Sphenoidal rostrum

rostrum sphenoidale

Vomerorostral canal

canalis vomerorostralis

Sphenoidal concha

concha sphenoidalis

Opening of the sphenoidal sinus

apertura sinus sphenoidalis

Foramen rotundum

foramen rotundum

Foramen ovale

foramen ovale

Foramen spinosum

foramen spinosum

Sphenoidal emissary foramen

foramen venosum

Foramen petrosum

foramen petrosum

Cerebral surface

facies cerebralis

Orbital surface

facies orbitalis

Maxillary surface

facies maxillaris

Temporal surface

facies temporalis

Frontal margin

margo frontalis

Squamous margin

margo squamosus

Zygomatic margin

margo zygomaticus

Parietal margin

margo parietalis

Impressions of the cerebral gyri

impressiones digitatae

Impressions of the cerebral gyri

juga cerebralia

Arterial grooves

sulci arteriosi

Inferior orbital fissure

fissura orbitalis inferior

Infratemporal crest

crista infratemporalis

Infratemporal surface

facies infratemporalis

Spine of the sphenoid bone

spina ossis sphenoidalis

Sulcus of the auditory tube

sulcus tubae auditivae

Superior surface

facies superior

Inferior surface

facies inferior

Anterior margin

margo anterior

Posterior margin

margo posterior

Jugum sphenoidale

jugum sphenoidale

Optic canal

canalis opticus

Anterior clinoid process

processus clinoideus anterior

Superior orbital fissure

fissura orbitalis superior

Medial plate

lamina medialis

Lateral plate

lamina lateralis

Pterygoid notch

incisura pterygoidea

Pterygoid fossa

fossa pterygoidea

Scaphoid fossa

fossa scaphoidea

Pterygospinous process

processus pterygospinosus

Pterygoid canal

canalis pterygoideus

Pterygoid hamulus

hamulus pterygoideus

Groove of the pterygoid hamulus

sulcus hamuli pterygoidei

Vaginal process

processus vaginalis

Palatovaginal groove

sulcus palatovaginalis

Vomerovaginal groove

sulcus vomerovaginalis