As a person ages the occipital bone fuses with other bones of the cranium. The surgeon can address other nerves that may be contributing to the problem, such as the lesser occipital nerves and the dorsal occipital nerves. By the twenty-fifth year this cartilaginous plate is ossified, and the occipital and sphenoid form a continuous bone. A short, bony canal called the hypoglossal canal anterior condyloid foramen is present at the base of each of these condyles. The upper two fossæ are triangular and lodge the occipital lobes of the cerebrum; the lower two are quadrilateral and accommodate the hemispheres of the cerebellum. The two occipital lobes are the smallest of four paired lobes in the. The term 'occipital' is derived from the Latin word 'occiput', which in turn is derived from the prefix 'ob' which means against and 'caput' which means head.
The occipital articulates with six bones: the two parietals, the two temporals, the sphenoid, and the atlas. From this protuberance the upper division of the cruciate eminence runs to the superior angle of the bone, and on one side of it generally the right is a deep groove, the sagittal sulcus, which lodges the hinder part of the superior sagittal sinus; to the margins of this sulcus the falx cerebri is attached. The groove on the right side is usually larger than that on the left, and is continuous with that for the superior sagittal sinus. Out of the 22 bones that form the human skull, 8 bones form the cranium. The jugular process, which is a quadrilateral-shaped plate of bone, runs sideways from the posterior half of the condyle.
Causes of Occipital Fractures An occipital fracture occurs as a result of sudden, blunt trauma to the base of the skull at the occipital bone. In four-footed animals the head hangs from the end of the , and the foramen magnum is placed posteriorly. Condylar fossa lies behind each condyle, and the opening for the condylar canal lies at the bottom of the fossa. The emissary veins connecting veins in the head and the scalp that drain blood from the dural sinuses to veins outside the skull pass through these canals from the transverse sinus. The two lateral sections are located on either side of the foramen magnum.
To the margins of this sulcus are attached the falx cerebri. The capsules of the atlanto-occipital articulations are attached to the margins of condyles. On its lower surface, about 1 cm. The occipital, like the other cranial the outer and inner tables, between which is the cancellous tissue or diploë; the bone is especially thick at the ridges, protuberances, condyles, and anterior part of the basilar part; in the inferior fossæ it is thin, semitransparent, and destitute of diploë. The lateral angles are situated at the extremities of the grooves for the transverse sinuses: each is received into the interval between the mastoid angle of the parietal and the mastoid part of the temporal.
Muscle tissue connects the occipital condyles to the atlas, or the first cervical vertebra at the top of the neck. On the lateral margins of this surface are faint grooves for the inferior petrosal sinuses. On each side, where the superolateral and inferolateral borders meet, lies the lateral angle. Several muscles are attached to the outer surface of the squama, thus: the superior nuchal line gives origin to the Occipitalis and Trapezius, and insertion to the Sternocleidomastoideus and Splenius capitis: into the surface between the superior and inferior nuchal lines the Semispinalis capitis and the Obliquus capitis superior are inserted, while the inferior nuchal line and the area below it receive the insertions of the Recti capitis posteriores major and minor. In human , the foramen magnum has continued to move forward as an aspect of to walking on two legs, until the head is now balanced vertically on top of the vertebral column.
There is not one test to diagnose occipital neuralgia. The seam, or suture, between the occipital and the sphenoid closes between ages 18 and 25, that with the parietals between ages 26 and 40. Grooves for the transverse sinus run horizontally from the left and right of the internal occipital protuberance and continue into the indentations or grooves for the sigmoid sinus. In the upper part of the internal occipital crest, a small depression is sometimes distinguishable; it is termed the vermian fossa since it is occupied by part of the vermis of the cerebellum. The episodes of intense pain may only last for a few minutes or seconds, but tenderness around the nerves may persist afterward.
The occipital bone is placed on the spinal column and creates a joint which helps the head move. These articulate with the atlanto-occipital joint first cervical vertebra C1. Located laterally to the foramen magnum on either sides, the condylar parts consist of two kidney-shaped prominences. Occipital lobe epilepsies are etiologically idiopathic, symptomatic, or cryptogenic. The lower division serves as a site for attachment to the falx cerebelli. The lateral parts are situated at the sides of the foramen magnum; on their under surfaces are the condyles for articulation with the superior facets of the atlas.
The occipital bone , situated at the back and lower part of the cranium, is trapezoid in shape and curved on itself. Nuchal lines are curved lines or ridges on the external surface, where muscles and ligaments of the neck and back attach to the skull. The margins of the transverse occipital sulcus serve as a site of attachment for the tentorium cerebelli a compartment or fold created by the dura mater, which is outermost membrane that encloses the brain. The lower division of the cruciate eminence is prominent, and is named the internal occipital crest; it bifurcates near the foramen magnum and gives attachment to the falx cerebelli; in the attached margin of this falx is the occipital sinus, which is sometimes duplicated. The posterior section of the bone is often triangular in shape, with the apex pointing upwards.