Instagram id- drsingh_akash
The inferior surface of the base of the skull, exclusive of the mandible, is bounded in front by the incisor teeth in the maxillæ; behind, by the superior nuchal lines of the occipital; and laterally by the alveolar arch, the lower border of the zygomatic bone, the zygomatic arch and an imaginary line extending from it to the mastoid process and extremity of the superior nuchal line of the occipital. It is formed by the palatine processes of the maxillæ and palatine bones, the vomer, the pterygoid processes, the under surfaces of the great wings, spinous processes, and part of the body of the sphenoid, the under surfaces of the squamæ and mastoid and petrous portions of the temporals, and the under surface of the occipital bone. when present they transmit the nasopalatine nerves. At either posterior angle of the hard palate is the greater palatine foramen, for the transmission of the descending palatine vessels and anterior palatine nerve; and running forward and medialward from it a groove, for the same vessels and nerve. Behind the posterior palatine foramen is the pyramidal process of the palatine bone, perforated by one or more lesser palatine foramina, and marked by the commencement of a transverse ridge, for the attachment of the tendinous expansion of the Tensor veli palatini. Projecting backward from the center of the posterior border of the hard palate is the posterior nasal spine, for the attachment of the Musculus uvulæ. n their vertical and 1.25 cm. in their transverse diameters. They are separated from one another by the vomer, and each is bounded above by the body of the sphenoid, below by the horizontal part of the palatine bone, and laterally by the medial pterygoid plate of the sphenoid. At the superior border of the vomer may be seen the expanded alæ of this bone, receiving between them the rostrum of the sphenoid. Near the lateral margins of the alæ of the vomer, at the roots of the pterygoid processes, are the pharyngeal canals. The pterygoid process presents near its base the pterygoid canal, for the transmission of a nerve and artery. The medial pterygoid plate is long and narrow; on the lateral side of its base is the scaphoid fossa, for the origin of the Tensor veli palatini, and at its lower extremity the hamulus, around which the tendon of this muscle turns. The lateral pterygoid plate is broad; its lateral surface forms the medial boundary of the infratemporal fossa, and affords attachment to the Pterygoideus externus.
Behind the nasal cavities is the basilar portion of the occipital bone, presenting near its center the pharyngeal tubercle for the attachment of the fibrous raphé of the pharynx, with depressions on either side for the insertions of the Rectus capitis anterior and Longus capitis. At the base of the lateral pterygoid plate is the foramen ovale, for the transmission of the mandibular nerve, the accessory meningeal artery, and sometimes the lesser superficial petrosal nerve; behind this are the foramen spinosum which transmits the middle meningeal vessels, and the prominent spina angularis (sphenoidal spine), which gives attachment to the sphenomandibular ligament and the Tensor veli palatini. Lateral to the spina angularis is the mandibular fossa, divided into two parts by the petrotympanic fissure; the anterior portion, concave, smooth bounded in front by the articular tubercle, 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.