Occipital bone . It joins the parietal bones along the “lamboid” suture and forms the back and base of the skull , has a large opening on its underside called the Foramen magnum, through which the nerve fibers of the brain pass and They enter the spinal canal to become part of the spinal cord. Rounded processes called “occipital condyles” that are found on each side of the foramen magnum, join with the first vertebra of the spinal column. The union of the sutures, sagittal and lamboid, is called Lambda.
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- 1 Features
- 2 Occipital scale
- 3 lateral masses
- 4 Sources
- Basilar process. Quadrilateral in shape, between the occipital hole behind and the body of the sphenoid in front. Four edges: anterior, posterior and two lateral. Two faces:
- Inferior or exocranial, it carries the pharyngeal tubercle in the midline towards the limit of its posterior third, on which the pharyngeal aponeurosis and the superior pharyngeal constrictor muscle are inserted. Ahead of the tubercle is a depression that houses Luschka’s pharyngeal gland, called the Pharyngeal fossa. From the tubercle towards the back some ridges of anterior concavity, called muscular ridges. In front of these other so-called synostosis, the small anterior rectus of the head is inserted between them, in front of the Synostosis the great anterior rectus muscle of the head is inserted.
- Superior or endocranial, transversely concave, channel shape, houses the bulb and the annular protuberance, with the name of basilar canal. The lateral edges of the basilar process are articulated in the temporal rock by means of fibrocartilage, its upper lip with the lower petrous sinus; its anterior border welded to the body of the sphenoid, the posterior one in front of the occipital foramen.
- Posteroinferior or exocranial face: convex, in the midline starting from the occipital foramen, the external occipital crest ending in the external occipital protuberance. On both sides the superior occipital curved line extends (up to the mastoid process); the trapezium is inserted in its lower lip and the occipital one in the upper lip. The concave inferior occipital curved line starts from the middle of the ridge and ends at the jugular process. Inserts the small posterior rectus and the small oblique inside. the two curved occipital lines limit a rough surface where the large complex is to be inserted inside and the small oblique on the outside. The external occipital protuberance and the superior occipital curved line correspond to the scalp and occipital muscle.
- Anterosuperior or endocranial face, concave, in the midline the internal occipital ridge. It bifurcates into two branches that are lost at the edges of the occipital hole, the internal occipital protuberance ends above, the lateral sinus channels depart from it on the sides. Above the longitudinal canal, for the superior longitudinal sinus. The confluence of these channels corresponds to the Herofilo dam . The internal occipital crest and the channels divide the surfaces into two cerebral fossae above and two cerebellar ones
- The upper edgesare jagged and articulate with the posterior edge of the parietals, the lower ones with the mastoid region of the temporals. the scale presents an upper angle that matches that of the parietals and two lower ones attached to the lateral occipital masses.
- Superior or endocranial face, in the anterior part the occipital tubercle, behind a channel where the spinal, pneumogastric and glossopharyngeal nerves slide, below and in front of the occipital tubercle an anterior condylar hole that gives way to the great hypoglossal nerve.
- Inferior or exo-cranial faceon each side of the occipital foramen a convex, elliptical and smooth projection whose middle part carries a strangulation, articulate with the atlas and are called occipital condyles, outside each condylar a precondylar fossa, at the bottom of which there is an anterior condylar hole, behind another retrocondylar fossa leads to the posterior condylar hole, on the external side the lateral rectus muscle of the head is inserted.
- The outer edgedivided into two parts by the jugular process. In front of this process, the edge is part of the posterior torn hole, behind it articulates with the temporal mastoid region.
- The anterior part of the external borderpresents the jugular spine that is viewed with the spinal of the temporal rock, dividing the torn hole into two parts. The posterior gives rise to the internal jugular vein and the anterior divided into two parts: the glossopharyngeal nerve passes through the anterior and the spinal and pneumogastric nerve through the posterior.
- Structure. The lateral masses and the basilar process by spongy tissue and thin sheets of compact. Two compact fabric with diploe inside for the scale.
- Ossification. At the end of the second month of fetal life, two centers for the basilar process, two for the lateral masses. It joins the cerebellar and cerebral portions through two centers. The basilar portion, one is basiotic and the other basioccipital, leaving the imprint of the Poirier synostotic crest. A secondary center for the occipital hole and two for the upper part of the scale, which give rise to a triangular bone called epactal or interparietal.