Occipital Bone Explained

Overview

The occipital bone is a cranial bone located at the base of the skull and the primary bone of the occiput, which is the back of the head. The occipital bone is a flat bone with a large surface area for muscle attachment. Between the skull and the head surface, there are a total of five layers of skin and subcutaneous tissue. From the inside to the outside, these include a layer of periosteum, loose areolar connective tissue, epicranial aponeurosis, dense connective tissue, and the skin with hair.

If you are interested in knowing all the details about the structure, function, vascularisation, and most common diseases of the occipital bone, keep reading this article!

Animation showing the occipital bone at the base of the cranium. Image by Anatomography

Structure

The occipital bone is classified as a flat bone just like other cranial bones (parietal and frontal bones). It is classified into separate parts due to its extensive attachments and innervations. The widest oval-shaped opening located at the base of the cranium is known as the foramen magnum, and this sits in the cranial fossa. At the edges of the foramen magnum are the lateral parts, additionally referred to as the exoccipitals. The basilar element is a thick, relatively quadrilateral piece in the front of the foramen magnum and directed in the direction of the pharynx. The squamous element is cured as compared to the basilar element.

Superior view of the skull base showing the foramen magnum in the occipital bone. Image by OpenStax College

Due to its embryonic derivation from paraxial mesoderm (instead of neural crest, from which many different craniofacial bones are derived), it’s been posited that the occipital bone as an entire might be taken into consideration as a large vertebra enlarged to guide the brain.

Superior view of the skull base. Image by OpenStax College

Function

The basic function of the occipital bone comes out to be the protection of the skull and the cranium. Is present at the base of the skull posteriorly and is the primary bone of the occiput. It is a major flat bone of the skull that has two primary functions. One is the protection of the base of the skull and the other is the wide floor for the attachment of the muscles of the head and neck. The scalp, which includes 5 layers, covers the bone. The occipital bone is the handiest cranial bone to connect with the cervical backbone. It has many crucial functions; however, its maximum crucial function is in defence of your brain. Another function is that it provides a passage for the spinal cord through the foramen magnum, which is accessed by the medulla oblongata, meninges, spinal root of cranial nerve XI, vertebral arteries, anterior and posterior spinal arteries, the tectorial membrane, and alar ligaments.

Illustration of the layers of the scalp, showing the layer of periosteum, loose areolar connective tissue, epicranial aponeurosis, dense subcutaneous connective tissue, and the skin with hair. Image by Frank Gaillard.

Neurovascular Supply

The occipital bone and the region is supplied mainly by the occipital artery and drained by the occipital vein. The occipital artery extends out from the carotid artery, but it is very deep from the posterior digastric. The hypoglossal nerve winds around the occipital artery.

The occipital artery is a posterior department of the outside carotid artery, placed withinside the posterior part of the neck and the occipital area of the pinnacle.

The occipital artery elements are numerous muscle tissue of the posterior neck in conjunction with trapezius, sternocleidomastoid and occipitofrontalis muscle tissue. Additionally, it offers off meningeal branches to the dura mater and cutaneous branches to the pores and skin of the neck, auricle and occipital area of the pinnacle.

The lateral muscle of the occipital bone is the rectus capitis lateralis, helping flex the pinnacle laterally. This muscle gets innervation from the spinal nerves C1 to C2 and gets arterial deliver through the deep cervical artery.

Illustration of the arteries and nerves in the skull, showing the occipital nerve and occipital artery. Image by StatPearls Publishing

Clinical Relevance and Asociated Disorders

When someone is born, their occipital bone isn’t always absolutely hardened, and it takes up to 6 years for the hardening to absolutely complete. Any troubles with the improvement of occipital bone can result in fitness issues. 

For example, if the occipital bone is misaligned, this additionally reasons misalignment of the backbone, inflicting ache.

The occipital bone is touchy to the birthing procedure and in a few times can grow to be injured or broken for the duration of childbirth. The occipital bone also can be laid low with different traumas or injuries, which includes vehicle accidents, sports activities injuries, and falls, ensuing in intellectual fitness or continual fitness troubles. Analysis of those malformations suggests that the occipital bone is number one affected in those disorders.

Craniovertebral Junction (CVJ) Disorders

The CVJ consists of the occipital bone, atlas (C1), and axis (C2), in conjunction with a community of complicated nerve and vascular structures. The occipital bone, atlas, and axis are answerable for a maximum of the backbone’s rotation, extension, and flexion—certainly put, no different vicinity to your backbone movements extra than the CVJ.

Upper Cervical Spine Disorder

Your health practitioner might also additionally name your head and higher neck circumstance a craniovertebral junction abnormality or a craniocervical disorder (cranio means cranium and cervical means neck). These names talk over with the equal institution of situations that arise at the bottom of the cranium and the start of the backbone.

Though it’s far rare, this prognosis may be very severe and ought to spark off a person to find pressing clinical care. Other kinds of contamination also can arise inside the neck. Infection can arise inside the bone or intervertebral disc. This is an extra not unusual place in older sufferers who might also additionally have a susceptible immune system.

Occipital Horn Syndrome

Occipital horn syndrome is characterized by the presence of lesions in the base of the skull. These are dystonic lesions present on the skull base diagnosed by the MRI brain. Trapizious and the sternocliedomastoid muscles attach to the base of the skull on the occiput. Occipital horns may be palpated or documented through cranial imaging. Patients with OHS show off dysautonomia, lax pores and skin and joints, bladder diverticula, inguinal hernias, and vascular tortuosity.

References
  1. Olivier G. Biometry of the human occipital bone. Journal of anatomy. 1975 Dec;120(Pt 3):507.
  2. LIST CF. Neurologic syndromes accompanying developmental anomalies of occipital bone, atlas and axis. Archives of Neurology & Psychiatry. 1941 Apr 1;45(4):577-616.
  3. Shapiro R, Robinson F. Embryogenesis of the human occipital bone. American Journal of Roentgenology. 1976 May 1;126(5):1063-8.
  4. Wescott DJ, Moore-Jansen PH. Metric variation in the human occipital bone: forensic anthropological applications. Journal of Forensic Science. 2001 Sep 1;46(5):1159-63.
  5. Cool SM, Hendrikz JK, Wood WB. Microscopic age changes in the human occipital bone. Journal of Forensic Science. 1995 Sep 1;40(5):789-96.
  6. Rusbridge C, Knowler SP. Inheritance of occipital bone hypoplasia (Chiari type I malformation) in Cavalier King Charles Spaniels. Journal of Veterinary Internal Medicine. 2004 Sep;18(5):673-8.

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