Sphenoid Bone

Os sphenoidale

For medical students3 min readUpdated 2026-10-10

The sphenoid bone is a complex, unpaired, pneumatized bone located centrally at the base of the skull. It consists of a massive central body and several projecting processes: the paired lesser and greater wings, and the vertically oriented pterygoid processes.

Bone typeUnpaired, pneumatized

StructureBody, lesser and greater wings, pterygoid process

Wing foraminaForamen rotundum, ovale, and spinosum

Key landmarkSella turcica with hypophysial fossa

Body Structure (Corpus)

The body of the sphenoid bone is cuboidal in shape. Inside, it contains air-filled cavities known as the sphenoid sinuses (Sinus sphenoidales), which are divided by the intersinus septum (Septum sinuum sphenoidalium). On the anterior wall, these sinuses open via apertures, adjacent to which lie the sphenoidal conchae (Conchae sphenoidales).

Each surface of the body has distinct anatomical features:

Posterior surface fuses with the basilar part of the occipital bone. Initially, this junction is a synchondrosis (cartilaginous), which ossifies into a synostosis with age.
Lateral surfaces feature the carotid sulcus (Sulcus caroticus), bounded posteriorly by the sphenoid lingula (Lingula sphenoidalis).
Anterior surface forms the sphenoidal crest (Crista sphenoidalis) in the midline, which transitions inferiorly into the sphenoidal rostrum (Rostrum sphenoidale).
Superior surface faces the cranial cavity. In its center lies the notable sella turcica, containing the hypophysial fossa (Fossa hypophysialis) that houses the pituitary gland. The sella is bounded anteriorly by the tuberculum sellae (Tuberculum sellae) with the middle clinoid processes, and posteriorly by the dorsum sellae (Dorsum sellae), which terminates in the posterior clinoid processes. Anterior to the sella is the prechiasmatic sulcus (Sulcus prechiasmaticus), followed by the jugum sphenoidale (Jugum sphenoidale).

Lesser Wings (Alae minores)

The lesser wings project laterally from the body of the sphenoid. Their superior surfaces face the cranial cavity (contributing to the anterior cranial fossa), while their inferior surfaces form the superior wall of the orbit (orbital surface, Facies orbitalis).

Anterior clinoid processes (Processus clinoidei anteriores) terminate the lesser wings posteriorly and medially. At the base of each lesser wing lies the optic canal (Canalis opticus). The space between the lesser and greater wings forms the critical superior orbital fissure (Fissura orbitalis superior).

Greater Wings (Alae majores)

The greater wings feature a complex spatial organization. Each wing presents five surfaces:

Cerebral surface (Facies cerebralis) — faces the middle cranial fossa.
Orbital surface (Facies orbitalis) — forms the lateral wall of the orbit.
Temporal surface (Facies temporalis).
Infratemporal surface (Facies infratemporalis) — separated from the temporal surface by the infratemporal crest (Crista infratemporalis).
Maxillary surface (Facies maxillaris) — forms the superior wall of the pterygopalatine fossa.

The greater wing articulates with neighboring bones via four borders: zygomatic, frontal, parietal, and squamous.

On the cerebral surface, just inferior to the superior orbital fissure, lies a series of critical foramina:

Foramen rotundum (Foramen rotundum). Close by, an inconstant emissary sphenoidal foramen (Foramen venosum) may occasionally be found.
Slightly lateral and posterior is the foramen ovale (Foramen ovale).
Further lateral and posterior lies the foramen spinosum (Foramen spinosum).
As an anatomical variant, the foramen petrosum (Foramen petrosum) may sometimes be located between them.

On the infratemporal surface, the posterior border of the wing forms the spine of the sphenoid bone (Spina ossis sphenoidalis), alongside the sulcus for the auditory tube (Sulcus tubae auditivae).

Pterygoid Process (Processus pterygoideus)

This paired process projects vertically downward from the sphenoid body. It is formed by two plates fused anteriorly: the lateral plate (Lamina lateralis) and the medial plate (Lamina medialis).

The posterior margin of the lateral plate bears the pterygospinosus process (Processus pterygospinosus). The medial plate curves inferiorly into the pterygoid hamulus (Hamulus pterygoidei), marked by the hamular sulcus.

Inferiorly, the plates diverge to form the pterygoid notch (Incisura pterygoidea). In the articulated skull, the pyramidal process of the palatine bone fits tightly into this notch, collectively forming the pterygoid fossa (Fossa pterygoidea). Superior to this fossa lies the scaphoid fossa (Fossa scaphoidea).

Projecting from the base of the medial plate is the vaginal process (Processus vaginalis), which participates in forming the palatovaginal and vomerovaginal sulci. Piercing the base of the pterygoid process anteroposteriorly is the pterygoid canal (Canalis pterygoideus).

Mnemonic

The foramina of the greater wing (from anterior to posterior) can be remembered as ROS: Rotundum, Ovale, Spinosum.

Frequently asked questions

What passes through the foramen rotundum of the sphenoid bone?

The maxillary nerve passes from the cranial cavity into the pterygopalatine fossa through the foramen rotundum. This structure is the second division of the trigeminal nerve (V2) and provides sensory innervation to the maxilla, nasal cavity, palate, and midface.

What passes through the optic canal of the sphenoid bone?

The optic nerve (CN II) and the ophthalmic artery pass through the optic canal. The ophthalmic artery runs alongside the optic nerve, positioned lateral to it.

What passes through the foramen spinosum of the sphenoid bone?

The middle meningeal artery, middle meningeal veins, and a meningeal branch of the mandibular nerve pass through the foramen spinosum. The middle meningeal artery enters the cranial cavity here to supply the dura mater.

What passes through the superior orbital fissure?

The ophthalmic nerve (CN V1), along with the oculomotor (CN III), trochlear (CN IV), and abducens (CN VI) cranial nerves, pass from the cranial cavity into the orbit. Vascular structures passing through include the superior ophthalmic vein and occasional meningeal branches from the ophthalmic artery.

Which parts of the sphenoid bone contribute to the orbital walls?

The following parts of the sphenoid contribute to the orbit:

Lesser wings (Alae minores) — the inferior surface forms the superior orbital wall (roof).
Greater wings (Alae majores) — the orbital surface forms the lateral orbital wall.
Body (Corpus) — the lateral surface contributes to the medial orbital wall region.

What passes through the pterygoid canal?

The artery of the pterygoid canal and the nerve of the pterygoid canal (vidian nerve) pass through the canal. The artery is a branch of the maxillary artery, while the nerve is formed by the union of the greater petrosal and deep petrosal nerves.

What passes through the foramen ovale of the sphenoid bone?

The mandibular nerve (CN V3), the third mixed division of the trigeminal nerve, exits the cranial cavity through the foramen ovale. Additionally, emissary veins connecting the pterygoid venous plexus to the cavernous sinus frequently pass through this area.

Which sinuses are located within the sphenoid bone?

The paired sphenoid sinuses (Sinus sphenoidales) are located within the body of the bone; they are pneumatized spaces separated by an intersinus septum.

Where is the sella turcica located and what does it contain?

The sella turcica is located on the superior surface of the sphenoid body. At its center is the hypophysial fossa, which houses the pituitary gland.

What structures form the superior orbital fissure?

It is the cleft bounded superiorly by the lesser wing and inferiorly by the greater wing of the sphenoid bone.

Go deeper

Boundaries and landmarks of the sella turcica: processes and sulci
Variant anatomy of greater wing foramina (foramen venosum and petrosum)
Contribution of greater wing surfaces to cranial fossae
Mechanics of pterygoid fossa formation with the palatine bone
Vaginal process sulci: palatovaginal and vomerovaginal canals