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Structure

Skull

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The skull is the bony skeleton of the head, consisting of the neurocranium that encloses the brain and the viscerocranium that forms the facial skeleton. Its foramina transmit the cranial nerves and the major vessels of the head.

Terminologia Anatomica (Latin): Cranium · Open in the 3D atlas

Location

At the top of the vertebral column, articulating with the atlas at the occipital condyles (atlanto-occipital joint); the mandible is the only mobile skull bone, via the temporomandibular joint.

Structure

Neurocranium: frontal, two parietal, two temporal, occipital, sphenoid and ethmoid bones. Viscerocranium: maxillae, zygomatic, nasal, lacrimal, palatine, vomer, inferior nasal conchae and mandible. Main sutures: coronal, sagittal, lambdoid and squamous. Neonatal fontanelles: anterior (closes at about 18 months to 2 years) and posterior (about 2 to 3 months), with variation. Cranial base: anterior, middle and posterior cranial fossae.

Blood supply

At group level: nutrient and diploic vessels from the meningeal arteries (notably the middle meningeal artery) and from the superficial temporal, occipital and posterior auricular branches of the external carotid artery. Diploic veins drain to the dural venous sinuses and emissary veins.

Innervation

At group level the periosteum and dura are supplied mainly by branches of the trigeminal nerve (frontal, zygomatic, auriculotemporal, supraorbital) and upper cervical nerves (greater and lesser occipital); the facial skeleton is supplied by trigeminal divisions.

Function

It protects the brain and sense organs, provides attachment for the muscles of mastication and facial expression and for the cervical muscles, supports the airway and the dentition, and transmits neurovascular structures through foramina such as the optic canal, superior orbital fissure, foramen rotundum, foramen ovale, foramen spinosum, internal acoustic meatus, jugular foramen, hypoglossal canal and foramen magnum.

Clinical correlations

Skull-base fractures may cause CSF leak, raccoon eyes, Battle sign or cranial nerve palsies. Pterion fracture risks middle meningeal artery injury and epidural haematoma. The sinuses (frontal, ethmoid, maxillary, sphenoid) are a source of infection spreading to the orbit and cavernous sinus. Raised intracranial pressure may cause tonsillar herniation through the foramen magnum. Premature suture fusion (craniosynostosis) alters skull shape.

Common exam points

  • Neurocranium: frontal, parietal (2), temporal (2), occipital, sphenoid, ethmoid.
  • Sutures: coronal, sagittal, lambdoid; anterior fontanelle closes at about 18 months to 2 years (variable).
  • Foramina: optic canal (CN II), superior orbital fissure (III, IV, V1, VI), rotundum (V2), ovale (V3), spinosum (middle meningeal artery), jugular (IX-XI), hypoglossal canal (XII).
  • Pterion: junction of frontal, parietal, temporal, sphenoid; underlies the middle meningeal artery.
  • Three cranial fossae: anterior (frontal lobes), middle (temporal lobes), posterior (cerebellum, brainstem).

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Netter FH. Atlas of Human Anatomy. Elsevier — Tier 3 (textbook)

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