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Sphenoid Bone

The sphenoid bone is the most complex bone of the human body. Because of its shape, it is also known as the "wasp bone". It makes up most of the middle part of the base of the skull and contributes to the floor of the middle cranial fossa.

In this article you will find out all about the anatomy of the sphenoid bone, its parts, borders, and development.

Anatomy

There are four main parts to the sphenoid bone: the body (corpus), the lesser and greater wings (alae minores et majores) and the pterygoid processes.

Sphenoid bone

Sphenoid bone

Body

The body is the most centrally positioned portion. Anteriorly it contributes to the nasal cavity, laterally it builds the medial wall of the optic canal. Superiorly the body forms the sella turcica, the hypophyseal fossa and the dorsum sellae.

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Anatomy and landmarks of the sphenoid bone.

They contain the anterior and posterior clinoid processes respectively. The clivus slopes posterior to the body. The sphenoidal sinuses are located in the sphenoid body behind the nasal cavity and divided by a septum.

Body of sphenoid bone - ventral view

Body of sphenoid bone - ventral view

Lesser wings

The lesser wings arise superolaterally from the sphenoid body where they form the optic canal (→ optic nerve, ophthalmic artery). The inferior surface participates in the lateral margin of the orbit while the superior surface forms part of the cranial cavity.

Lesser wings of sphenoid bone - ventral view

Lesser wings of sphenoid bone - ventral view

Greater wings

The greater wings arise posterolaterally from the body. Their lateral surfaces form the infratemporal surfaces, their anterior surfaces make up part of the posterior aspect of the lateral wall of the orbit.

They contain two important openings near their roots: the foramen rotundum (→ maxillary nerve) and the foramen ovale (→ mandibular nerve, accessory meningeal artery). The foramen spinosum (→ middle meningeal vessels, spinous nerve [branch of mandibular nerve]) lies at the posterior margin of the greater wings.

Greater wings of sphenoid bone - ventral view

Greater wings of sphenoid bone - ventral view

Between the body, lesser and greater wings is a large opening known as the superior orbital fissure where numerous nerves and vessels pass through (→ superior ophthalmic vein, ophthalmic nerve and its branches, abducent nerve, oculomotor nerve, trochlear nerve).

Pterygoid processes

The pterygoid processes are extensions of the basal surface of the sphenoid body. The processes contain two canals known as the pterygoid canal (→ major petrosal nerve, deep petrosal nerve, vessels of pterygoid canal) and the palatovaginal (or pharyngeal) canal (→pharyngeal nerve). A hamulus extends bilaterally from each medial pterygoid plate.

Pterygoid processes - ventral view

Pterygoid processes - ventral view

Borders

The sphenoid bone has a common border with the frontal bone (via the sphenofrontal suture), the parietal bone (via the the sphenoparietal suture), the squamous part of the temporal bone (via the sphenosquamosal suture) and the occipital bone (via the spheno-occipital suture). As the sphenoid and occipital bone fuse during puberty ("tribasilar bone") the spheno-occipital suture disappears by the age of 25.

Sphenoid bone - sagittal view

Sphenoid bone - sagittal view

Osseous development

The body and lesser wings of the sphenoid bone mature through classic endochondral ossification, whereas the pterygoid processes undergo intramembranous ossification.

The development of the greater wings of the sphenoid bone are exceptional since they are the only bony structures of the skull which go through both endochondral and intramembranous ossification.

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Show references

References:

  • Neil S. Norton, Frank H. Netter: Netter’s Head and Neck Anatomy for Dentistry, 2nd edition, Elsevier Saunders, p. 34, 49, 50, 55.
  • M. Schünke, E. Schulte, U. Schumacher: Prometheus - Kopf, Hals und Neuroanatomie, 2nd edition, Thieme (2009), p.34-35
  • Friedrich Anderhuber, Franz Pera, Johannes Streicher: Waldeyer Anatomie des Menschen, 19th edition, De Gruyter (2012), p.715-719

Author:

  • Dr. Alexandra Sierosławska

Illustrators:

  • Sphenoid bone - Samantha Zimmerman
  • Body of sphenoid bone - ventral view - Samantha Zimmerman
  • Lesser wings of sphenoid bone - ventral view - Samantha Zimmerman
  • Greater wings of sphenoid bone - ventral view - Samantha Zimmerman
  • Pterygoid processes of sphenoid bone - ventral view - Samantha Zimmerman
  • Sphenoid bone - sagittal section - Yousun Koh 
© Unless stated otherwise, all content, including illustrations are exclusive property of Kenhub GmbH, and are protected by German and international copyright laws. All rights reserved.

Related Atlas Images

Sphenoid bone

Midsagittal skull

Superior view of base of the skull

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