Anatomy & Organs

Occipital Bone – Structure, Function & Diseases

Occipital bone

The occipital bone ( Os occipitale ) is a part of the brain skull. The bone consists of three parts and not only contains various openings, but also serves as an attachment point for tissues. In skull base fractures , the occipital bone can fracture and trisomy 18 often results in a large occiput.

What is the occipital bone?

The bones of the skullcap form a rounded vault that contains the brain . They provide support for the soft tissue of the complex organ and shield it from direct contact with the environment. The occipital bone is one of the bones that make up the brain skeleton (neurocranium). In total, the brain skeleton has seven different bones, the entire skull – including the facial skull – comprises 22.

The occipital bone is located at the back of the head, where it can be found between the sphenoid bone (os), temporal bone (os temporale), and parietal bone (os parietale). The anatomy also knows the occipital bone under the technical term “Os occipitale”. Like all bones, the flat skull consists of a framework of tissue that only fully hardens in the course of physical development.

Anatomy & Structure

The occipital bone is made up of three parts that are normally fused together: the pars squamosa, the pars lateralis and the pars basilaris. The pars squamosa lies below (dorsal) the foramen magnum.

The foramen magnum is a large opening in the brain skull through which the elongated medulla ( medulla oblongata ) leaves the posterior cranial fossa ( fossa cranii posterior ) and merges into the spinal cord . The pars squamosa is bowl-shaped and develops from two subunits. The occipital plate arises from four centers from where the bone tissue grows together. In contrast, the neck plate of the pars squamosa develops from two nuclei from the seventh week of development.

The pars lateralis forms the lateral areas of the occipital bone and arises from a nucleus about a week later. The pars lateralis has an occipital condyle on each side, which is part of the atlanto-occipital joint (articulatio atlantooccipitalis). The pars basilaris forms the part of the occipital bone that closes off the rostral part of the skull towards the middle of the head. It has approximately the shape of a square and also arises from a center during physical development.

Function & Tasks

As part of the cranium, the occiput has the task of supporting and shielding the brain. It also contains or provides support for numerous structures.

Together with the temporal bone, the occiput forms the posterior fossa. It contains the cerebellum , midbrain , pons and medulla. The latter protrudes through the foramen magnum, located at the bottom of the occipital bone. The pars squamosa has bony prominences and depressions. One such deepening is the transverse sinus sulcus, in which the transverse sinus runs. The transverse sinus is a blood conduit that drains venous blood from the skull .

Another depression in the pars squamosa of the occipital bone is the sulcus sinus sigmoidei . It contains the sigmoid sinus, another venous blood conduit. The two sulci are on the inside of the pars squamosa. There, the protuberantia occipitalis interna forms a small protrusion on which the cerebral sickle ( falx cerebri ) is attached. The skin separates the two hemispheres of the brain. On the outside of the pars squamosa, the protuberantia occipitalis externa also offers an attachment point for the hood or trapezius muscle (musculus trapezius).

The skull is connected to the atlas via the atlanto-occipital joint at the pars lateralis of the occipital bone . The atlas represents the top cervical vertebra (C1) and thus forms the beginning of the spine . On the inside of the pars lateralis lies the tuberculum jugulare, which covers the hypoglossal canal as a bony prominence. In some cases, the jugular tubercle also provides a depression for cranial nerves IX–XI. The pars lateralis also functions as the insertion point of a neck muscle, the musculus rectus capitis lateralis , with the help of its processus jugularis .

In addition, the occipital bone forms an internal protrusion at the pars lateralis known as the pharyngeal tubercle. This is where the rectus capitis anterior muscle, the pharyngeal suture (raphe pharyngis) and the longus capitis muscle attach. The clivus of the pars lateralis forms the border between the posterior craniose fossa and the median craniose fossa.

Diseases

Injuries to the head can lead to a fracture of the base of the skull , which often also affects the occiput. Medicine distinguishes between a frontobasal fracture involving the nose and a laterobasal fracture, in which the temporal bone also breaks.

Possible symptoms include monocle/spectacle hematoma, leakage of cerebrospinal fluid and blood , and impaired consciousness . If cranial nerves or parts of the brain are damaged, additional neurological symptoms can occur, which indicate, for example, cranial nerve failure. However, some symptoms can also resemble the clinical picture of a stroke . In some cases, the fracture of the base of the skull leads to bleeding in the eye area . People may feel a throbbing in the eye, or the eyeball may protrude from the swelling. Doctors then speak of an exophthalmosor Protrusio bulbi.

In connection with trisomy 18, the occipital bone of those affected is often noticeably large. The genetic condition is also known as Edwards syndrome and can manifest itself in many different ways. Malformations and short stature are typical. In most cases (around 90%), trisomy 18 leads to death before birth and the mortality rate of children born with Edwards syndrome is also very high. Treatment usually focuses on the symptoms because medicine cannot treat the cause of the genetic disease. In some cases, supportive measures are necessary, such as artificial nutrition.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.