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Skull

Contents

Components & Features

The human skull consists of about 22 to 30 single bones which are mostly connected together by ossified joints, so called sutures. The skull is divided into the braincase (cerebral cranium) and the face (visceral cranium). Its main task is the protection of the most important organ in the human body: the brain. The brain is almost entirely enclosed by the cerebral cranium with the exception of the foramen magnum and other foramina at the skull base which serve as entry and exit point for blood vessels and cranial nerves.

Skull - ventral view

Skull - ventral view

The braincase consists of the skullcap (calvarium) and the skull base. The skull cap is made up of the pairs of parietal bones and parts of the frontal bone as well as the occipital bone. The most important sutures in the human skull are:

  • the coronal suture (between the frontal and parietal bone)
  • the sagittal suture (dividing both the parietal bones)
  • the lambdoidal suture (running horizontally between the occipital bone and both parietal bones)

These are the three most significant of all 33 sutures which are formed by the human skull bones.

The skull base is the caudal boundary of the cerebral cranium. Looking at it from the inside it can be subdivided into the anterior, middle and posterior cranial fossae. The skull base comprises parts of the frontal, ethmoid, sphenoid, occipital and temporal bones.

Cranial Fossae (Middle cranial fossa) - cranial view

Cranial Fossae (Middle cranial fossa) - cranial view

The face is referred to as all skull bones fronto-caudally connected to the cerebral cranium. Prominent representatives are the maxilla (upper jaw) and the mandible (lower jaw). The orbita and the nasal cavity are formed by the zygomatic, nasal, palatine, lacrimal bones, the vomer and the inferior nasal concha (lower turbinate).

Recommended video: Bones of the skull
Overview of the bones that make up the skull.

Foramina & Contents

Most foramina in which relevant nerves and blood vessels pass through are located at the base of the skull. In the following, the most important structures are discussed ordered by their location in the three cranial fossae.

Anterior Cranial Fossa

The anterior cranial fossa comprises a holey plate at the center, the so called cribriform plate (lamina cribrosa). The approximately 20 cribriform foramina serve as a passageway for the olfactory nerves to the olfactory mucosa in the nasal cavity.

Cribriform plate - medial view

Cribriform plate - medial view

Both the optic nerve and the ophthalmic artery pass through the optic canal which is centrally located on the sphenoid bone. The lesser wing of the sphenoid bone (ala minor) forms the dorsal boundary of the anterior cranial fossa.

Optic canal - cranial view

Optic canal - cranial view

Middle Cranial Fossa

The middle cranial fossa lies slightly deeper than the anterior cranial fossa. The superior orbital fissure which is bounded by the greater and lesser wings of the sphenoid bone contains the trochlear nerve, abducencs nerve, oculomotor nerve and ophthalmic nerve. The sella turcica is a depression in the sphenoid bone. In the center of the middle cranial fossa it forms the pituitary fossa in which the pituitary gland sits.

Superior orbital fissure - ventral view

Superior orbital fissure - ventral view

Further important foramina are the: 

Foramen ovale - cranial view

Foramen ovale - cranial view

Posterior Cranial Fossa

The largest opening in the skull is the foramen magnum. Here the brainstem leaves the skull and becomes the spinal cord. The foramen magnum is situated in the center of the posterior cranial fossa. It is separated from the middle cranial fossa by the dorsum sellae and the upper edge of the petrous bone.

Foramen magnum - cranial view

Foramen magnum - cranial view

Further important structures are the:

Jugular foramen - cranial view

Jugular foramen - cranial view

Foramina Summary

  • Cribriform plate - olfactory nerves
  • Optic canal - optic nerve, opthalmic artery
  • Superior orbital fissure - trochlear, abducens, oculomotor, and ophthalmic nerves
  • Foramen rotundum - maxillary nerve
  • Foramen ovale - mandibular nerve
  • Carotid canal - internal carotid artery
  • Foramen magnum - brainstem
  • Internal acoustic meatus - facial and vestibulocochlear nerves
  • Jugular foramen - internal jugular vein, glossopharyngeal nerve, vagus nerve, accessory nerve
  • Hypoglossal canal - hypoglossal nerve)
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Show references

References:

  • Lippert H.: Lehrbuch Anatomie, 6th edition (2003), Urban und Fischer Verlag/ Elsevier Verlag, p. 489-500
  • Benninghoff/Drenckhahn: Anatomie, Band 2, 16th edition (2004), p. 483-513
  • Putz R., Pabst R.: Sobotta Atlas der Anatomie des Menschen, 20th edition (1993), Urban & Schwarzenberg, p. 30-69

Author & Layout:

  • Christopher A. Becker
  • Achudhan Karunaharamoorthy

Illustrators:

  • Skull - ventral view - Yousun Koh
  • Cranial Fossae (Middle cranial fossa) - cranial view - Yousun Koh
  • Cribriform plate - medial view - Yousun Koh
  • Optic canal - cranial view - Yousun Koh
  • Superior orbital fissure - ventral view - Paul Kim
  • Foramen ovale - cranial view - Yousun Koh
  • Foramen magnum - cranial view - Yousun Koh
  • Jugular foramen - cranial view - 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.

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