The occipital bone (occiput) is the posterior part of the skull, covering for the cerebellum and it contains several bony landmarks that are important for anatomical reference and clinical assessment. Here are some key bony landmarks of the occiput:
External Occipital Protuberance (inion):
This is a prominent projection at the midline of the external surface of the occipital bone.
It serves as an attachment point for ligaments and muscles of the neck.
The inion or external occipital protuberance is the midline region of the occiput where bone is greatest in thickness.
The superior and inferior nuchal lines extend laterally and distally from the inion.
The transverse sinus is located in close proximity to the inion.
The area in the midline below the inion is an ideal location for screw insertion for occipital fixation as it is the thickest portion of the occiput.
There are three nuchal lines on the external surface of the occipital bone:
Superior Nuchal Line: Located above the external occipital protuberance, it serves as an attachment site for the epicranial aponeurosis.
Inferior Nuchal Line: Situated below the external occipital protuberance, it provides attachment for various neck muscles.
Highest Nuchal Line: A ridge connecting the external occipital protuberance to the mastoid part of the temporal bone.
These are rounded processes on either side of the foramen magnum, which articulate with the atlas (first cervical vertebra) to form the atlanto-occipital joint. This joint allows nodding or flexion and extension movements of the head.
This is a large opening at the base of the skull through which the spinal cord passes and connects to the brain.
External Occipital Crest:
A ridge that runs along the midline on the external surface of the occipital bone, extending from the external occipital protuberance to the foramen magnum.
Understanding these bony landmarks is crucial in fields such as anatomy, neurology, and orthopedics, as they provide reference points for various structures and play a role in the assessment of head and neck conditions.