The bone at the back of the head that contains the great hole through which the medulla passes to become the spinal cord
Occipital bone — it surrounds the foramen magnum.
Anatomy · Bones
Occipital bone
The back and base of the skull
Skull · cranium
The occipital bone is a single, curved, trapezoid bone forming much of the back and base of the skull. It contains the foramen magnum, through which the brainstem becomes the spinal cord, and its two condyles rest on the first cervical vertebra. It protects the cerebellum and the occipital lobes of the brain.
How to spot them
- ▸An unpaired, saucer-shaped bone at the back and underside of the skull
- ▸Contains the large hole, the foramen magnum, with a rounded condyle on each side
- ▸A palpable bump in the midline at the back, the external occipital protuberance (inion), with nuchal lines running out from it
- ▸Joined to the two parietal bones by the lambdoid suture
What to know
Two smooth, rounded condyles on its underside articulate with the topmost vertebra, the joint that allows nodding
Occipital bone — the atlanto-occipital joint.
The palpable midline bump at the back of the head, called the inion, is part of this bone
Occipital bone — the external occipital protuberance.
Ridges called the superior, inferior and supreme lines on its outer surface anchor muscles such as trapezius and semispinalis capitis
Occipital bone — the nuchal lines, nuchal meaning nape of the neck.
Grooves on its inner surface, arranged in a cross around an internal protuberance, are cut by the dural venous sinuses
Occipital bone — the cruciform eminence, with grooves for the transverse and superior sagittal sinuses.
The sloping, shallow groove on its basilar part in front of the foramen magnum supports the medulla oblongata
Occipital bone — the clivus, a landmark on cervical spine X-rays.
It meets the two parietal bones at a suture named for the Greek letter lambda
Occipital bone — the lambdoid suture.
Key ideas
- Three parts surround the foramen magnum: the squamous part behind, two condylar parts at the sides and the basilar part in front.
- The hypoglossal canal in the condylar part carries the twelfth cranial nerve; the jugular foramen lies between this bone and the petrous temporal bone.
Quick-fire facts
- •Occiput is Latin for the back of the head
- •Passing through the foramen magnum: the medulla oblongata, vertebral arteries, spinal accessory nerve roots, and the spinal arteries
- •Articulates with the two parietal bones, two temporal bones, the sphenoid and the atlas
- •The falx cerebri attaches to the internal occipital crest, and the internal occipital protuberance lies at the centre of the cruciform eminence
- •Protects the cerebellum and the occipital lobes, the visual cortex of the cerebrum
- •The clivus is a landmark for checking alignment at the atlanto-occipital joint, and the abducens nerve runs close to it
- •Infection from the scalp may reach the meninges by valveless emissary veins passing through the bone
- •The four nuchal lines (supreme, superior, median and inferior) mark attachments of scalp and neck muscles and the nuchal ligament
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Sources
- TeachMeAnatomy — The Occipital Bone
- OpenStax — Anatomy and Physiology 2e, 7.2 The Skull