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Inferior View of Petrous Apexes

Surgical Correlation

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Inferior view of a bony skull preparation showing landmarks and foramina between the greater wing of the sphenoid and the occipital bone. The largest foramen of the skull is the foramen magnum. It is an opening in the occipital bone. Anterior to this foramen on the undersurface of the clivus is a small midline elevation, the pharyngeal tubercle, for attachment of the superior pharyngeal constrictor muscle. Further anterior is the vomer bone forming the posterior edge of the nasal septum. Lateral to this are the bases of the pterygoid processes of the sphenoid containing the lateral and medial pterygoid plates. Lateral to these plates are the greater wings, containing in this view, the foramen ovale and foramen spinosum. The foramen lacerum is a triangular opening between the petrous apex, body of the sphenoid, and basilar part of the occipital bone. It is filled in life by fibrous cartilage. Lateral to the foramen spinosum is the sphenosquamosal suture. It borders the medial aspect of the articular tubercle that forms the anterior boundary of the mandibular fossa. The condyle of the mandible slides on its surface during jaw opening and closing. Along the posteromedial border of the mandibular fossa is the petrotympanic fissure for emergence of the chorda tympani. Within the petrous portion of the temporal bone one can observe the styloid process and opening of the carotid canal. Medial to the mastoid process is the stylomastoid foramen for the facial nerve and stylomastoid artery. Between the petrous bone and occipital bone is the jugular foramen that can be divided into two parts: a pars nervosa that contains the inferior petrosal sinus and the glossopharyngeal nerve, and a pars vascularis that contains the jugular bulb and the vagus and spinal accessory nerves. The needle in the image is shown traversing the hypoglossal canal for passage of the hypoglossal nerve. (Image courtesy of AL Rhoton, Jr.)

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