The external occipital protuberance (EOP) is a distinct bony prominence at the back of the skull. This anatomical landmark can often be felt by touch, serving as a reference point for various medical purposes.
Understanding Its Location
The external occipital protuberance is situated on the outer surface of the occipital bone, which forms the back and lower part of the skull. It lies centrally, around the middle of the squamous part of this bone. This projection is found at the junction where the skull meets the neck, making it a prominent feature of the posterior skull. Its appearance can vary, ranging from a smooth prominence to a more defined ridge or even a spine-like projection.
Finding It On Your Head
To locate your external occipital protuberance, gently place your fingers on the central back part of your head. Slowly move your fingers downwards towards your neck. You should feel a bony bump or ridge just above where your neck begins to curve forward. This palpable feature is a normal part of human anatomy, and its prominence can differ from person to person.
Why It Matters
The external occipital protuberance serves as an attachment point for several muscles and ligaments that stabilize and move the head and neck. The nuchal ligament, a strong fibrous band, extends from this protuberance down to the seventh cervical vertebra, providing support and limiting excessive head flexion. The trapezius muscle, a large muscle of the upper back and neck, originates from the EOP, contributing to shoulder and neck movements. The EOP also marks the beginning of the superior nuchal lines, which are bony ridges extending laterally and serve as attachment sites for other neck muscles.
Related Medical Insights
Because of its consistent location, the external occipital protuberance acts as a reference point in medical contexts. It can be used as a landmark in medical imaging, such as X-rays or CT scans, to orient and assess the skull and cervical spine. The area around the EOP can also be associated with pain conditions, including occipital neuralgia, which involves irritation or inflammation of nerves in this region. In some cases, an unusually prominent EOP, sometimes called an occipital spur, can become tender and cause localized discomfort.