Skull Flashcards
Neurocranium
portion of the skull enclosing the brain and its associated meninges. Regions: Calvaria and Cranial base.
Calvaria
skull cap
dome-like roof
Flat bones composing the calvaria are structured such that they have an internal portion of trebecular bone (diploe) sandwiched between two layers of compact bone (outer and inner tables)
Note: the frontal, maxilla, ethmoid and sphenoid contain air cells or sinuses that play a role in lightening the head and in phonation. These sinuses increase in size with age.
Cranial base
basicranium
floor
a. Osseous elements: frontal, ethmoidal, parietals, occipital, temporals, spehnoid
b. most of the bones forming the neurocranium are united by sutures
Viscerocranium
a. Portion of the skull forming the face (orbits, nasal cavities, mouth)
b. Osseous elements: maxilla, ethmoid, vomer, zygomatic, inferior nasal concha, palatine, lacrimal, mandible
Major sutures
Coronal: articulation between frontal and parietals
Sagittal: articulation between individual parietal bones
Lambdoid: articulation between parietals and the occipital
Squamosal: articulation between the squamous portion of temporal and parietal
Craniometric points of the skull
Nasion: mid-point of intersection of the two nasal bones and the frontal
Bregma: intersection of the sagittal and coronal sutures
Pterion: intersection of frontal, parietal, sphenoid (greater wing) and temporal
Lambda: intersection of the sagittal and lambdoid sutures
Inion: located at the external occipital protuberance
Asterion; intersection of the parietal, occipital and temporal
Frontal bone articulations/ major suture
articulates with: nasal, maxilla, zygomatic, parietals, lacrimal, ethmoid, sphenoid (greater and lesser wing); participates with nasal bones to form NASION.
Coronoal suture- articulation between frontal and parietal bones; ends at PTERION.
Note: in 8% of individuals, the sagittal suture bisects the frontal bone completely (metopic or frontal suture)
Frontal bone landmarks
- Glabella- centrally located elevation
- Frontal eminences- slightly raise elevations above the SUPERCILIARY ARCHES
- Superciliary arches- elevated area deep to location of eyebrows
Note: the FRONTAL AIR SINUS is located within the frontal bone deep to the glabella and superciliary arches.
- Orbital part or plate- portion of frontal bone located in medial superior orbit; also located in anterior cranial fossa
- Zygomatic process- portion that articulates with zygomatic bone
Foramina of the frontal bone
Supraorbital notch or foramen- notch or foramen in superior orbital margin
Nasal bone articulations
- Frontal, maxilla
- Participates with the frontal bone to form the NASION
- Participates with the maxilla to form the PIRIFORM APERTURE (bony margin of nose)
Nasal bone foramina
nasal foramen
Maxilla (houses maxillary air sinus) articulations/ sutures
- articulates with: frontal, nasal, lacrimal, ethmoid, zygomatic, inferior concha, palatine, vomer and maxilla
- intermaxillary sutur marks dual primordial origin
Maxilla landmarks
- anterior nasal spine- sharp prominence at base of piriform aperture
- forms majority of PIRIFORM APERTURE border
- INFRAORBITAL GROOVE on orbital portion
- INFRAORBITAL CANAL leading from groove to infraorbital foramen
- Maxillary tuberosity- located posterior to third maxillary molar (provides attachment for medial pterygoid muscle)
Maxilla processes
- Frontal
- Orbital
- Zygomatic
- ALVEOLAR PROCESSES (sockets for upper teeth)
- PALATINE- forms anterior 2/3 of hard palate
Maxilla foramina/ fissures
INFRAORBITAL FORAMEN
INCISIVE CANAL/ FORAMEN/ FOSSA
Posterior superior alveolar
Provides anterior border of PTERYGO/ SPHENOMAXILLARY FISSURE
Zygomatic bone articulations
frontal
maxilla
sphenoid
temporal
Zygomatic bone landmarks
frontal process
maxillary process
temporal process- with zygomatic process of temporal bone, forms the ZYGOMATIC ARCH
orbital surface
Zygomatic bone foramina
- Zygomatico-orbital- located on teh lateral wall of the orbit; leads to the two foramina listed below
- ZYGOMATICOFACIAL- located on lateral-anterior surface of zygomatic bone
- ZYGOMATICOTEMPORAL- located on posterior surface of zygomatic bone opening into temporal fossa.
Parietal bone articulations/ sutures
- Articulates with teh frontal bone via the coronal suture
- Articulates with the opposite parietal bone via the sagittal suture
- Articulates with the temporal bone via the squamosal suture
- Articulates with the occipital bone via the lambdoid suture
- Articulates with the sphenoid at the pterion and middle cranial fossa
Parietal bone landmarks
- Superior temporal line- marks attachment of temporalis fascia
- Inferior temporal line- marks perimeter attachment of temporalis muscle.
Parietal bone foramina
a singular parietal foramen conducting an emissary vein can be located parallel to the sagittal suture in near proximity to the lambdoid suture
Occipital bone regions
- Squamous- largest portion, saucer-like appearance posterior to foramen magnum
- BASILAR- TRAPEZOIDAL PORTION ANTERIOR TO FORAMEN MAGNUM
- lATERAL- PORTIONS LATERAL TO THE FORAMEN MAGNUM
Occipital bone articulations/ sutures
- Squamous portion articulates with the parietals (lambdoid suture), temporal bones
- Basilar portion fuses with the sphenoid at the dorsum sellae; rarely do the two bones actually articulate forming a cartilaginous joint
Occipital bone landmarks
- PROTUBERANCES: INTERNAL AND EXTERNAL
- NUCHAL LINES: SUPERIOR AND INFERIOR
- OCCIPITAL CONDYLES
- GROOVES FOR SUPERIOR AND TRANSVERSE SINUSES- located on internal surface of occiput; meet in the region of the internal occipital protuberance
Occipital bone foramina
- Foramen Magnum
- Condyloid canal- canal located deep to the occipital condyles located posterolateral to teh condyle passing to the jugular fossa (area deep to jugular foramen)
- Hypoglossal canal- canal passing from teh anterolateral rim of the internal surface of the foramen magnum laterallly to open anterior and superior to the occipital condyles.
Note: The jugular foramen is formed by the LACK of fusion of the temporal and occipital bones on the basal surface of the skull lateral to the occipital condyles.
Temporal bone regions
- Squamous
- Mastoid
- Tympanic
- Petrous
Temporal bone articulations
sphenoid, parietal, occipital, mandible
Temporal bone landmarks
- Mastoid process
- External acoustic meatus
- Zygomatic process
- Mandibular fossa
- Articular tubercle
- Styloid process
- Stylomastoid foramen
- Groove for the posterior belly of the digastrics (PBD) muscle
- Groove fro the occipital artery
- Mastoid foramen
- Jugular fossa
- Mastoid canaliculus
- Tympanic canaliculus
- Carotid canal
- Tympanic plate
- Petrotympanic fissure
- Bony portion of the auditory tube
- Petrous ridge
- Groove for the superior petrosal sinus- located on petrous ridge
- Tegmen tympani
- Hiatuses of the greater and lesser petrosal nn.
- Internal acoustic meatus
- Groove for the sigmoid sinus
Mastoid process
superior attachment point of SCM
External acoustic meatus
- opening of the auditory canal
Zygomatic process
- with temporal process of zygomatic forms ZYGOMATIC ARCH
Mandibular fossa
- articulates with condyle (head) of mandible
Articular tubercle
- ramp utilized by head of mandible; assists in opening the mouth
Styloid process
located on inferior surface of temporal bone, provides anchoring point for 3 muscles and 2 ligaments
Stylomastoid foramen
foramen posterior to styloid process
Mastoid foramen
located posterior to the groove for the PBD
Jugular fossa
point of non-union of temporal and occipital bones medial to styloid process
Mastoid canaliculus
tiny foramen/ canal on the lateral wall of the jugular fossa
Tympanic canaliculus
tiny foramen/ canal opening onto ridge between teh jugular foramen and carotid canal
Carotid canal
foramen directly anterior to jugular fossa