Henry Gray (18251861). Anatomy of the Human Body. 1918.
serves for the articulation of the condyle of the mandible; the posterior portion, rough and bounded behind by the tympanic part of the temporal, is sometimes occupied by a part of the parotid gland. Emerging from between the laminæ of the vaginal process of the tympanic part is the styloid process; and at the base of this process is the stylomastoid foramen, for the exit of the facial nerve, and entrance of the stylomastoid artery. Lateral to the stylomastoid foramen, between the tympanic part and the mastoid process, is the tympanomastoid fissure, for the auricular branch of the vagus. Upon the medial side of the mastoid process is the mastoid notch for the posterior belly of the Digastricus, and medial to the notch, the occipital groove for the occipital artery. At the base of the medial pterygoid plate is a large and somewhat triangular aperture, the foramen lacerum, bounded in front by the great wing of the sphenoid, behind by the apex of the petrous portion of the temporal bone, and medially by the body of the sphenoid and basilar portion of the occipital bone; it presents in front the posterior orifice of the pterygoid canal; behind, the aperture of the carotid canal. The lower part of this opening is filled up in the fresh state by a fibrocartilaginous plate, across the upper or cerebral surface of which the internal carotid artery passes. Lateral to this aperture is a groove, the sulcus tubæ auditivæ, between the petrous part of the temporal and the great wing of the sphenoid. This sulcus is directed lateralward and backward from the root of the medial pterygoid plate and lodges the cartilaginous part of the auditory tube; it is continuous behind with the canal in the temporal bone which forms the bony part of the same tube. At the bottom of this sulcus is a narrow cleft, the petrosphenoidal fissure, which is occupied, in the fresh condition, by a plate of cartilage. Behind this fissure is the under surface of the petrous portion of the temporal bone, presenting, near its apex, the quadrilateral rough surface, part of which affords attachment to the Levator veli palatini; lateral to this surface is the orifice of the carotid canal, and medial to it, the depression leading to the aquæductus cochleæ, the former transmitting the internal carotid artery and the carotid plexus of the sympathetic, the latter serving for the passage of a vein from the cochlea. Behind the carotid canal is the jugular foramen, a large aperture, formed in front by the petrous portion of the temporal, and behind by the occipital; it is generally larger on the right than on the left side, and may be subdivided into three compartments. The anterior compartment transmits the inferior petrosal sinus; the intermediate, the glossopharyngeal, vagus, and accessory nerves; the posterior, the transverse sinus and some meningeal branches from the occipital and ascending pharyngeal arteries. On the ridge of bone dividing the carotid canal from the jugular foramen is the inferior tympanic canaliculus for the transmission of the tympanic branch of the glossopharyngeal nerve; and on the wall of the jugular foramen, near the root of the styloid process, is the mastoid canaliculus for the passage of the auricular branch of the vagus nerve. Extending forward from the jugular foramen to the foramen lacerum is the petroöccipital fissure occupied, in the fresh state, by a plate of cartilage. Behind the basilar portion of the occipital bone is the foramen magnum, bounded laterally by the occipital condyles, the medial sides of which are rough for the attachment of the alar ligaments. Lateral to each condyle is the jugular process which gives attachment to the Rectus capitis lateralis muscle and the lateral atlantoöccipital ligament. The foramen magnum transmits the medulla oblongata and its membranes, the accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries, and the ligaments connecting the occipital bone with the axis. The mid-points on the anterior and posterior margins of the foramen magnum are respectively termed the basion and the opisthion. In front of each condyle is the canal for the passage of the hypoglossal nerve and a meningeal artery. Behind each condyle is the condyloid fossa, perforated on one or both sides by the condyloid canal, for the transmission of a vein from the transverse sinus. Behind the foramen magnum