External occipital protuberance
Part of the human skull

Near the middle of the squamous part of occipital bone is the external occipital protuberance, the highest point of which is referred to as the inion. The inion is the most prominent projection of the protuberance which is located at the posteroinferior (rear lower) part of the human skull. The nuchal ligament and trapezius muscle attach to it.
The inion (ἰνίον, iníon, Greek for the occipital bone) is used as a landmark in the 10-20 system in electroencephalography (EEG) recording. Extending laterally from it on either side is the superior nuchal line, and above it is the faintly marked highest nuchal line.
A study of 16th-century Anatolian remains showed that the external occipital protuberance statistically tends to be less pronounced in female remains.
Sources and credits
This article is adapted from the Wikipedia article “External occipital protuberance”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- External occipital protuberance - lateral view2.png by Polygon data is from BodyParts3D, CC BY-SA 2.1 jp
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