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occipital bone

 
Dictionary: occipital bone

n.
A curved, trapezoid compound bone that forms the lower posterior part of the skull; the occipital.


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Sports Science and Medicine: occipital bone
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Bone that forms part of the back and base of the cranium, and encloses the foramen magnum.

Medical Dictionary: occipital bone
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n.

A bone at the lower and posterior part of the skull, consisting of basilar, condylar, and squamous parts and enclosing the foramen magnum.

WordNet: occipital bone
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Note: click on a word meaning below to see its connections and related words.

The noun has one meaning:

Meaning #1: a saucer-shaped membrane bone that forms the back of the skull


Wikipedia: Occipital bone
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Bone: Occipital bone
Gray194.png
Sagittal section of skull. (Occipital bone is at right, in blue.)
Gray193.png
Base of the skull. Upper surface. (Occipital bone is at bottom, in blue.)
Gray's subject #31 129
Articulations the two parietals, the two temporals, the sphenoid, and the atlas  

The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the cranium, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal.

Contents

Foramen magnum

See also Foramen magnum

The foramen magnum (latin for large hole) is a large oval aperture with its long diameter antero-posterior; it is wider behind than in front where it is encroached upon by the condyles.

It transmits the medulla oblongata and its membranes, the accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the membrana tectoria and alar ligaments.moo

Angles

The superior angle of the occipital bone articulates with the occipital angles of the parietal bones and, in the fetal skull, corresponds in position with the posterior fontanelle.

The inferior angle is fused with the body of the sphenoid. The lateral angles are situated at the extremities of the grooves for the transverse sinuses: each is received into the interval between the mastoid angle of the parietal and the mastoid part of the temporal.

Borders

The superior borders extend from the superior to the lateral angles: they are deeply serrated for articulation with the occipital borders of the parietals, and form by this union the lambdoidal suture.

The inferior borders extend from the lateral angles to the inferior angle; the upper half of each articulates with the mastoid portion of the corresponding temporal, the lower half with the petrous part of the same bone.

These two portions of the inferior border are separated from one another by the jugular process, the notch on the anterior surface of which forms the posterior part of the jugular foramen.

Structure

The occipital, like the other cranial the outer and inner tables, between which is the cancellous tissue or diploë; the bone is especially thick at the ridges, protuberances, condyles, and anterior part of the basilar part; in the inferior fossæ it is thin, semitransparent, and destitute of diploë.

In other animals

In most vertebrates, the foramen magnum is surrounded by a ring of four bones. The basioccipital lies in front of the opening, the two exoccipitals lie to either side, and the larger supraoccipital lies to the posterior, and forms at least part of the rear of the cranium. In many bony fish and amphibians, the supraoccipital is never ossified, and remains as cartilage throughout life. In primitive forms the basioccipital and exoccipitals somewhat resemble the centrum and neural arches of a vertebra, and form in a similar manner in the embryo. Together, these latter bones usually form a single concave circular condyle for the articulation of the first vertebra.[1]

In mammals, however, the condyle has divided in two, a pattern otherwise seen only in a few amphibians. Most mammals also have a single fused occipital bone, formed from the four separate elements around the foramen magnum, along with the paired postparietal bones that form the rear of the cranial roof in other vertebrates.[1]

Additional images


See also

References

  1. ^ a b Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 221-244. ISBN 0-03-910284-X. 

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.


 
 

 

Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.  Read more
Sports Science and Medicine. The Oxford Dictionary of Sports Science & Medicine. Copyright © Michael Kent 1998, 2006, 2007. All rights reserved.  Read more
Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company Read more
WordNet. WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved.  Read more
Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Occipital bone" Read more