occipital bone

It is pierced by a large, oval opening, the foramen magnum, through which the cranial cavity communicates with the vertebral canal. It has two portions: scaly and basilar.

a) Squamous – curved blade that extends posterior to the occipital foramen.

b) Basilar – anterior to the occipital foramen and thick.


External face : posterior and convex. It has the following structures:

  • External Occipital Protuberance – located between the apex of the bone and the foramen magnum
  • External Occipital Crest
  • Supreme Occipital (Nucal) Line – site of insertion of the galea aponeurotic. The external occipital protuberance is located laterally
  • Superior Occipital (Nuchal) Line – located below the superior nuchal line
  • Inferior Occipital (Nuchal) Line – just below the superior nuchal line

Inner Face : located anteriorly. It has the following structures:

  • Cruciform Eminence – divides the inner face into four fossae
  • Internal Occipital Protuberance – point of intersection of the four divisions
  • Sagittal sulcus – houses the posterior portion of the superior sagittal sinus
  • Internal Occipital Crest – inferior portion of the cruciform eminence
  • Transverse Sinus Groove – lateral to the internal occipital bulge
  • Superior Occipital Fossa (Brain)
  • Inferior Occipital Fossa (Cerebellar)

Basic :

  • foramen magnum – large oval opening that gives passage to the medulla oblongata (brain stem – medulla) and its membranes (meninges), cerebrospinal fluid, nerves, arteries, veins and ligaments.

Side :

  • Occipital Condyles – are oval in shape and articulate with the 1st cervical vertebra (Atlas)
  • Hypoglossal Canal – small excavation at the base of the occipital condyle that gives exit to the hypoglossal nerve (12th cranial nerve) and entry to a meningeal branch of the ascending pharyngeal artery.
  • Condylar canal – next to the foramen magnum (gives the way to veins)
  • Jugular Process – located lateral to the occipital condyle

The Occipital articulates with six bones: Parietal (2), Temporal (2), Sphenoid and Atlas.

 Osso Occipital - Vista Externa
Source: SOBOTTA, Johannes. Atlas of Human Anatomy. 21 ed. Rio de Janeiro: Guanabara Koogan, 2000.

 Osso Occipital - Vista Interna
Source: SOBOTTA, Johannes. Atlas of Human Anatomy. 21 ed. Rio de Janeiro: Guanabara Koogan, 2000 .

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