The occipital bone is a cranial bone located at the base of the skull, specifically at the back of the head. It is a large, triangular-shaped bone that forms the posterior part of the skull, and it plays a crucial role in the structure and function of the head and neck.
Structure
The occipital bone is made up of several different parts, including the squamous part, the basilar part, and the condyles.
Squamous Part
The squamous part is the largest and most superior part of the occipital bone. It is thin and flat, and it forms the posterior part of the skull. The squamous part is composed of two layers of bone: the outer layer, called the cortical bone, and the inner layer, called the cancellous bone. The cortical bone is dense and hard, providing structural support and protection for the brain. The cancellous bone is spongy and porous, and it helps to reduce the weight of the skull.
Basilar Part
The basilar part is a thick, triangular-shaped part of the occipital bone that forms the base of the skull. It is located inferior to the squamous part and extends anteriorly towards the front of the skull. The basilar part is made up of two laminae, or thin plates, of bone that are joined together by a thin layer of cartilage. The basilar part supports the weight of the skull and helps to distribute the load evenly across the skull.
Condyles
The condyles are two rounded projections located at the posterior and lateral aspects of the occipital bone. They are part of the occipital condyles, which are responsible for articulating with the first cervical vertebra (C1), also known as the atlas. The occipital condyles allow for movement of the head and neck, such as nodding and turning.
Location
The occipital bone is located at the back of the head, posterior to the parietal bones and superior to the cervical vertebrae. It is the only bone of the skull that is completely posterior and not visible from the front or side. The occipital bone is bordered by several other bones, including the parietal bones superiorly, the temporal bones laterally, and the sphenoid bone anteriorly.
Function
The occipital bone has several important functions, including:
- Structural support: The occipital bone provides structural support and protection for the brain by forming the posterior part of the skull.
- Attachment of muscles: The occipital bone serves as the attachment site for several muscles of the neck and head, including the occipitalis, the sternocleidomastoid, and the splenius capitis. These muscles help to move and stabilize the head and neck.
- Articulation with the cervical vertebrae: The occipital bone articulates with the atlas (C1) via the occipital condyles, allowing for movement of the head and neck.
Clinical Significance
The occipital bone is often involved in a variety of medical conditions, including:
- The occipital bone can be fractured due to trauma, such as a fall or motor vehicle accident. These fractures can cause headaches, neck pain, and difficulty with movement of the head and neck.
- Occipital neuralgia is a type of headache that is caused by irritation or compression of the occipital nerves, which run through the occipital bone. Symptoms of occipital neuralgia include sharp or stabbing pain in the back of the head, neck, or scalp, as well as tenderness or sensitivity to touch in these areas.
- Spina bifida occulta is a congenital condition that is characterized by a small gap in the spine that does not close completely. This gap is usually located in the occipital bone and may cause no symptoms or may cause problems with muscle tone, balance, or coordination.
- A Chiari malformation is a condition in which the cerebellum, a part of the brain, extends into the spinal canal through an opening in the occipital bone. This can cause a variety of symptoms, including headaches, neck pain, numbness, weakness, and balance problems.
