Sphenoid bone

Sphenoid bone: Anatomy & FunctionKey facts about the anatomy of the sphenoid bone.
~ 3 min

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.

Sphenoidal bone (os sphenoidale)
Sphenoidal bone (os sphenoidale)

The sphenoid bone consists of several parts:

  • Body of the sphenoid bone (corpus ossis sphenoidalis)

Body of the sphenoid bone (corpus ossis sphenoidalis)
Body of the sphenoid bone (corpus ossis sphenoidalis)
  • Greater wing (ala major) – paired

    Greater wing (ala major)
    Greater wing (ala major)
  • Lesser wing (ala minor) – paired

    Lesser wing (ala minor)
    Lesser wing (ala minor)
  • Pterygoid process (processus pterygoideus) – paired

    Pterygoid process (processus pterygoideus)
    Pterygoid process (processus pterygoideus)

    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.

    Sphenoidal sinus (sinus sphenoidalis)
    Sphenoidal sinus (sinus sphenoidalis)

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

    Sella turcica (sella turica)
    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.

    Hypophysial fossa (fossa hypophysialis)
    Hypophysial fossa (fossa hypophysialis)

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

    Tuberculum sellae (tuberculum sellae)
    Tuberculum sellae (tuberculum sellae)
    Dorsum sellae (dorsum sellae)
    Dorsum sellae (dorsum sellae)

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

    Prechiasmatic sulcus (sulcus prechiasmaticis).
    Prechiasmatic sulcus (sulcus prechiasmaticis).

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

    Posterior clinoid process (processus clinoideus posterior)
    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).

    Carotid sulcus (sulcus caroticus)
    Carotid sulcus (sulcus caroticus)

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

    Sphenoidal lingula (lingula sphenoidalis)
    Sphenoidal lingula (lingula sphenoidalis)

    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.

    Sphenoidal crest (crista sphenoidalis)
    Sphenoidal crest (crista sphenoidalis)

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

    Sphenoidal rostrum (rostrum sphenoidale)
    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).

    Sphenoidal choncha (concha sphenoidalis)
    Sphenoidal choncha (concha sphenoidalis)
    Sphenoidal sinus (aperture sinus sphenoidalis)
    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 rotundum (foramen rotundum)
    Foramen rotundum (foramen rotundum)
  • Foramen ovale (foramen ovale), through which the mandibular nerve passes

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

    Foramen spinosum (foramen spinosum)
    Foramen spinosum (foramen spinosum)

    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)

    Cerebral surface (facies cerebralis)
    Cerebral surface (facies cerebralis)
  • Orbital surface (facies orbitalis)

    Orbital surface (facies orbitalis)
    Orbital surface (facies orbitalis)
  • Maxillary surface (facies maxillaris)

    Maxillary surface (facies maxillaris)
    Maxillary surface (facies maxillaris)
  • Temporal surface (facies temporalis)

    Temporal surface (facies temporalis)
    Temporal surface (facies temporalis)

    And 4 margins:

  • Frontal margin (margo frontalis)

    Frontal margin (margo frontalis)
    Frontal margin (margo frontalis)
  • Squamosal margin (margo squamosis)

    Squamosal margin (margo squamosis)
    Squamosal margin (margo squamosis)
  • Zygomatic margin (margo zygomaticus)

    Zygomatic margin (margo zygomaticus)
    Zygomatic margin (margo zygomaticus)
  • Parietal margin (margo parietalis)

    Parietal margin (margo parietalis)
    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.

    Inferior orbital fissure (fissura orbitalis inferior)
    Inferior orbital fissure (fissura orbitalis inferior)

    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.

    Infratemporal crest (crista infratemporalis)
    Infratemporal crest (crista infratemporalis)

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

    Infratemporal surface (facies infratemporalis)
    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.

    Sphenoidal bone (spina ossis sphenoidalis)
    Sphenoidal bone (spina ossis sphenoidalis)

    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.

    Sulcus of the auditory tube (sulcus tubae auditivae)
    Sulcus of the auditory tube (sulcus tubae auditivae)

    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).

    Jugum sphenoidale (jugum sphenoidale)
    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.

    Optic canal (canalis opticus)
    Optic canal (canalis opticus)

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

    An anterior clinoid process (processus clinoideus anterior)
    An anterior clinoid process (processus clinoideus anterior)

    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.

    Superior orbital fissure (fissura orbitalis superior)
    Superior orbital fissure (fissura orbitalis superior)

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

  • Medial plate (lamina medialis)

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

    Lateral plate (lamina lateralis)
    Lateral plate (lamina lateralis)

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

Pterygoid notch (incisura pterygoidea)
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.

Pterygoid fossa (fossa pterygoidea)
Pterygoid fossa (fossa pterygoidea)

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).

Scaphoid fossa (fossa scaphoidea)
Scaphoid fossa (fossa scaphoidea)

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

Pterygospinous process (processus pterygospinosus)
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.

Pterygoid canal (canalis pterygoideus)
Pterygoid canal (canalis pterygoideus)

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

Pterygoid hamulus (hamulus pterygoideus)
Pterygoid hamulus (hamulus pterygoideus)

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

Pterygoid hamulus (sulcus hamuli pterygoidei)
Pterygoid hamulus (sulcus hamuli pterygoidei)

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

Vaginal process (processus vaginalis)
Vaginal process (processus vaginalis)

Two grooves adhere to it

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

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

Vomerovaginal groove (sulcus vomerovaginalis)
Vomerovaginal groove (sulcus vomerovaginalis)
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
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