What Is the Inion?

Andy Josiah
Andy Josiah
The inion is the most noticeable protrusion of the occipital bone.
The inion is the most noticeable protrusion of the occipital bone.

The inion is the most noticeable or pronounced protrusion of the occipital bone, which is one of the bones that comprise the skull. In fact, the name “inion” is a Greek term that is actually used for the occipital bone. Thus, in some cases, synonyms like “occipital bone,” among others, are used for the protrusion, even if they are not entirely accurate.

The trapezius muscle is attached to the inion.
The trapezius muscle is attached to the inion.

Forming part of the much larger, upper part of the human skull, called the cranium, the occipital bone is shaped like a saucer, or a trapezoid with curved ends. It is located at the cranium’s rear and lower regions. The occipital bone has a scale-like structure called the occipital squama, near the middle of the external occipital protuberance.

The inion is located at the external occipital protuberance. Thus, the protrusion is sometimes referred to as the external occipital protuberance. The inion, however, is the highest point of this particular area of the occipital bone. It is not synonymous with the external occipital protuberance itself.

Two types of muscles are attached to the inion: the ligamentum nuchae and the trapezius muscle. Also known as the nuchal ligament, or paxwax, the ligamentum nuchae is one of the strong fibrous cords of the neck. It is named after the median nuchal line, which is one of the occipital bone’s four external curved lines that runs from the external occipital protuberance. The other type of muscle attached to the bump, the trapezius, runs lengthwise to the middle section of the spine. The trapeziuses are responsible for moving the scapulae, or shoulder blades, enabling movement of the head and providing support to the arms.

The inion is also anatomically notable for being referred to as an Anatolian bump, which is when the inion is larger than usual. The protrusion gets its name from the alleged high number of occurrences among the people of Anatolia — the westernmost region of Asia, which is mostly covered by the Republic of Turkey. There is no research or proof, however, to substantiate that contention, nor is this variant of the inion restricted to the Anatolian region. Legend has it that in Nazi Germany, the protrusion was considered an indication of membership of the “master race” or “Aryan race,” a concept of white supremacy especially dominant in the late 19th and early 20th centuries. Additionally, some Swedes consider the bump as the mark of descendants of Walloons, some of who migrated to Sweden from Belgium as early as the 17th century.

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Discussion Comments


@browncoat - It does say that it was a legend that they checked for the inion.

And unfortunately, looks can prove things about ancestry, just through simple genetics. You probably wouldn't have a prominent inion unless you inherited it from somewhere (genetics isn't quite that simple all the time, but close enough).

Of course, the idea of being judged on genetic material alone is foolish for a lot of reasons. Not least the fact that we still have such an incomplete understanding of it. It wasn't long ago that people thought you could divine personalities from the bumps of the head.

It's one of the reasons that human eugenics is such a terrible idea. We have no idea what we'd be tampering with, what we'd lose. And that's not even going into the ethics of it.


It's so ridiculous what meaning people will attach to superficial differences.

Like the idea that the Nazis would check for this bump on someone's head to see if someone was a member of the Aryan race.

Well, I have a bump and I happen to be a mixed race child, so I can see that theory would have to be tossed out the window.

Of course, they wouldn't take it to realize that superficial things like how you look or who your ancestors are have little to no impact on what kind of person you are. And, in fact, looks or bumps can't even prove anything about your ancestry.

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    • The inion is the most noticeable protrusion of the occipital bone.
      By: Gufh
      The inion is the most noticeable protrusion of the occipital bone.
    • The trapezius muscle is attached to the inion.
      By: high_resolution
      The trapezius muscle is attached to the inion.