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The Skull The Bones of the Skull --8 Paired bones (bilateral) a. parietal b. temporal c. zygomatic d. nasal e. lacrimal f. inferior concha g. palatine h. maxilla --6 Unpaired bones a. frontal b. ethmoid c. occipital d. sphenoid e. vomer f. mandible Sutures of the Skull (where bones of skull are joined by fibrous types of joints syncondroses) --sagittal suture: b/w parietal bones --coronal suture: b/w frontal and parietal bones --lambdoid suture: separates occipital bone from parietal and temporal bones Superior Aspect of the Skull --Surface Landmarks a. vertex: highest point of the skull b. bregma: at junction of the sagittal and coronal sutures Anterior Aspect of the Skull --Surface Landmarks a. glabella: median elevation b/w the eyebrows (superciliary arches) --Bones a. frontal bone *superciliary arches: extend laterally from glabella *supraorbital notch: in upper margin of orbit b. nasal bones c. maxillary bone d. zygomatic bone e. mandible *Body: landmarks (external/internal) --mental protuberance --mental foramen (below 2nd molar) --oblique line (runs upward and backward) --alveolar process (contains the lower teeth) --submandibular fossa (below myelohyoid line, for submandibuar gland) *Ramus: landmarks (external/internal) --mandibular notch (upper border of ramus) --coronoid process (anterior to notch) --mandibular foramen (middle of ramus, for vessels and nerves) --lingula (spine at mandibular foramen for sphenomandibular ligament) *Condylar process: landmarks (posterior to notch) --head/condyle (articulates in mandibular fossa of temporal bone) --neck (just below the head) *Angle: junction of the posterior and inferior borders of the mandible Lateral Aspect of the Skull --Surface Landmarks a. pterion: circular area formed by the junction of the frontal, sphenoid, parietal, and squamous part of temporal bones --Bones a. mandible bone: with condylar process, coronoid process, ramus, and angle --Structures c. zygomatic arch d. temporal line e. external auditory meatus --Infratemporal Fossa: inferior to the temporal fossa a. Fissures *inferior orbital fissure *pterygomaxillary fissure to the pterygopalatine fossa --Pterygopalatine fossa: located below the apex of the orbit a. Sphenopalatine foramen: to the nasal cavity, medialy Posterior Aspect of the Skull --Surface Landmarks a. lambda: at junction of lambdoid and sagittal sutures b. inion: center of the external occipital protuberance c. external occipital protuberance: diamond shaped structure at the inion d. superior nuchal line: extends laterally from EOP to provide attachment for several muscles e. inferior nuchal line: provides attachment for rectus capitis posterior major and minor muscles Orbit --Margins *supraorbital notch/foramen: at medial 1/3 *medial margin *fossa/groove for lacrimal sac *nasolacrimal canal: downward continuation of lacrimal fossa --Walls *superior wall/roof: fossa for the lacrimal gland (anterolaterally) *apex: the optic foramen *lateral wall: superior orbital fissure (b/w lesser and greater wings of sphenoid) and inferior orbital fissure (b/w greater wing of sphenoid above and maxillary and palatine bones below) *Inferior wall/floor: infraorbital groove and canal *Medial wall: thinnest wall of the orbit; orbital plate of ethmoid (lamina papyracea) Inferior Aspect of the Skull --Bones a. occipital bone *foramen magnum *occipital condyles: 2 large protuberances lateral to foramen magnum *hypoglossal canal: above and ant. to each of the occipital condyles *basilar part: ant. to foramen magnum, joins body of sphenoid bone --pharyngeal tubercle: at center of basilar part of occiput b. temporal bone *Squamous Part: mandibular fossa: articulates with head of condylar process articular tubercle: at ant. part of mandibular fossa *Styloid Part: styloid process *Mastoid Part: mastoid process stylomastoid foramen: b/w styloid process and mastoid process (TRANSMITS CN VII) *Petrous part: jugular foramen (TRANSMITS CN IX, X, XI) carotid canal (TRANSMITS internal carotid artery, and sympathetic nerve plexus) foramen lacerum c. sphenoid bone: consists of a body, greater wings, lesser wings, and pterygoid process *Greater wings: lateral to lateral pterygoid plates foramen ovale: posterior to lateral pterygoid plate (TRANSMITS mandibular n.) foramen spinosum: posterolateral to foramen ovale *Pterygoid Process: extend downward from juction of body and greater wing of sphenoid bone each pterygoid process separates into 2 plates (lateral pterygoid plate and medial pterygoid plate whose inf. extremity forms the pterygoid hamulus for tendon of tensor veli palatini muscle) d. Posterior nasal aperture/choana: posterior opening of the nasal cavity e. vomer: forms the posterior inferior part of the nasal septum f. Palatine Bone *Perpendicular plate/vertical part pterygopalatine canal: TRANSMITS greater palatine nerves and vessels *Horizontal plate pyramidal process g. Maxilla *Incisive fossa/foramen: in midline behind the incisors in the foramen are 2 incisive canals (for terminal branch of the sphenopalatine artery and nasopalatine nerve) Cranial Cavity --Anterior cranial fossa a. Frontal bone *orbital plates: form the roof of the orbits b. Ethmoid bone *cribiform plate: the superior surface of the ethmoid bone that appears in the anterior cranial fossa (has perforations for the transmission of olfactory nerves) *crista galli: triangular process projecting superiorly from the mdiline of the cribiform plate, the posterior border serves as attachment for the falx cerebri c. Sphenoid bone *lesser wings of sphenoid: behind the orbital plates of the frontal bone --Middle Cranial fossa a. sphenoid bone: body of sphenoid *optic/chiasmatic groove: for optic chiasm *optic canals/foramen: transmit the optic nerves *anterior clinoid processes *tuberculum sellae: posterior to the chiasmatic groove *sella turcica (Turkish saddle): deep depression behind the tuberculum sellae --hypophyseal fossa: deepest part (lodges pituitary) --dorsum sellae: posterior boundary of sella turcica --posterior clinoid processes b. greater wings of sphenoid and squamous and petrous parts of temporal *superior orbital fissure: between greater and lesser wings of sphenoid (TRANSMITS CN III, CN IV, CN V1, CN VI, and superior ophthalmic vein) *foramen rotundum: immediately below the medial end of the superior orbital fissure (TRANSMITS CN V2) *foramen ovale: posterior to foramen rotundum (TRANSMITS CN V3, and accessory meningeal artery) *foramen spinosum: posterior and lateral to foramen ovale (TRANSMITS middle meningeal artery) *foramen lacerum c. temporal bone *arcuate eminence: rounded elevation caused by the projection of the superior/anterior semicircular canal *hiatus and canal for the greater petrosal nerve: branch of the nervus intermedius (in association with CN VII) carrying PREganglionic PARAsympathetic nerve fibers to the pterygoid/Vidian canal *hiatus and canal for the lesser petrosal nerve: carrying PREganglionic PARAsympathetic nerve fibers (association w/ CN IX) --Posterior Cranial Fossa a. Sphenoid bone *dorsum sellae *clivus: slopes down and posteriorly b. Petrous temporal *internal auditory meatus: TRANSMITS CN VII, VIII, and nervus intermedius c. Occipital bone *foramen magnum *hypoglossal canals *internal occipital protuberance --transverse grooves --groove for sigmoid sinusees