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
Tympanic plate
bony floor of auditory canal
Petrotympanic fissure
anterior to tympanic plate, posterior and medial to the mandibular fossa
bony portion of the auditory tube
directly medial to the spine of the sphenoid
Petrous ridge
highest point of the sphenoid in the middle cranial fossa
Tegmen tympani
elevation over middle ear anterior to petrous ridge
Hiatuses of the greater and lesser petrosal nn.
twin openings located anterior to petrous ridge medial to tegmen tympani; greater is superior, medial and posterior; lesser is inferior, lateral and anterior
Internal acoustic meatus
large opening located posterior to petrous ridge approximately 3/4 of the distance of the petrous ridge, lateral to medial
Groove for the sigmoid sinus
on floor of posterior cranial fossa; opens into jugular fossa
anesthesia on tip of nose. What nerve?
V1
Sphenoid bone articulations
zygomatic, frontal, parietal, temporal, occipital, maxilla, vomer
Note: foramen lacerum is formed by the LACK of fusion of the sphenoid, petrous portion of the temporal and basilar portion of the occipital. In life, the foramen does not exist as the junction of these three bones is united by cartilage. The carotid canal opens superior to the foramen lacerum transmitting the internal carotid artery.
Sphenoid bone landmarks
Body containing sphenoid sinus greater wings lesser wings lateral and medial pterygoid plates hamulus of the medial pterygoid plate scaphoid fossa pterygoid fossa optic canals prechiasmatic groove anterior clinoid processes sella turcica (Turkish saddle) - tuberculum sellae - hypohpyseal fossa - dorsum sellae Clivus
Body of sphenoid bone
contains sphenoid sinus- midline portion of sphenoid
Greater wings of sphenoid
large lateral extensions from teh body visible in the orbit, at the pterion and in the middle cranial fossa
lesser wings of sphenoid
delicate superolateral extensions from teh body; articulate with internal surfaces of frontal and parietal bones
Lateral and medial pteygoid plates
bilateral twin inferior extensions from teh body
Hamulus of the medial pterygoid plate
hook at the extreme inferior portion of the medial pterygoid plate
scaphoid fossa (of sphenoid bone)
depression at base of medial pterygoid plate
Pterygoid fosssa
area between pterygoid plates
Optic canals
opening beneath anterior edge of lesser wing; opens into orbit as optic foramen
Prechiasmatic groove
groove on superior surface of body of sphenoid connecting orbital canals
anterior clinoid processes
posteriorly directed extensions of the lesser wings of the sphenoid
Sella turcica
Turkish saddle
superior surface of the body of the sphenoid between anterior and posterior clinoid processes (bed posts); composed of the:
a. Tuberculum sellae- elevation located directly posterior to the prechiasmatic groove
b. hypophyseal fossa- depression oin the body of the sphenoid housing the pituitary gland
c. Dosum sellae- square elevation on posterior portion of body of sphenoid; posterior clinoid processes are superior extensions of the dorsum sellae
Clivus
area of fusion of body of the sphenoid and basilar portion of the occipital bone, slopes posteriorly and inferiorly to the foramen magnum
Foramina/ canals/ fissures of the sphenoid
superior orbital fissure Rotundum Ovale Spinosum Pterygoid canal pharyngeal canal
Superior orbital fissure
gab between greater and lesser wings; communicates middle cranial fossa with the orbit
Foramen rotundum
opening on medial anterior portion of the greater wing of sphenoid directly posterior to superior orbital fissure; opens into pterygopalatine fossa
Foramen ovale
large oval opening posterolateral to rotundum; opens into infratemporal fossa
Foramen Spinosum
small opening located posterolateral to ovale; opens into infratemporal fossa directly medial to the spine of the sphenoid
Pterygoid canal
paired openings through the body of the sphenoid inferior to the sphenoid sinus at the roots of the pterygoid wings; opens into pterygopalatine fossa
Pharyngeal canal (palatovaginal)
canal between the inferior surface of the body of the sphenoid and the vertical portion of the palatine bone.
Palatine bone
- Small, irregular (L-shaped) bone insinuated between the maxilla and sphenoid bones
- Possesses a horizontal part and a vertical part
- Horizontal part forms posterior portion of the hard palate and floor of the posterior nasal cavity; fusion of both horizontal portions forms posterior nasal spine
- Vertical part forms a portion of the posterior lateral wall of the nasal cavity and contributes to a small portion of the posterior orbit
Articulations of the palatine bone
- Palatal shelves of the maxilla
- inferior nasal concha
- Maxilla near tuberosity
- Lateral pterygoid plate opposite tuberosity of maxilla
- Medial pterygoid plate
- Body of sphenoid near optic foramen
Foramina of palatine bone
- Vertical part- sphenopalatine foramen/ notch made complete by opposing portion of sphenoid
- Horizontal part- lesser palatine foramina
- Pterygopalatine canal- canal directly inferior to the pterygopalatine fossa located between the vertical part of the palatine bone, posterior maxilla and anterior wall of the pterygoid portion of the sphenoid
Lacrimal bone articulations, landmarks, etc.
a. Articulations: orbital portions of the maxilla, frontal and ethmoid bones
b. Landmarks- lacrimal crest
c. With frontal process of maxilla defines LACRIMAL FOSSA (area between anterior and posterior lacrimal crests)
d. LACRIMAL CANAL- drains lacrimal fossa to nasal cavity
Ethmoid bone articulations
frontal nasal bones vomer sphenoid nasal septal cartilage
Ethmoid bone landmarks
orbital plate
cribriform plate with olfactory foramina and crista galli
perpendicular plate
air cells
anterior and posterior ethmoidal foramina (as viewed from the orbit)
Superior and middle concha
Bulla ethmoidalis- rounded elevation under middle concha- opening for maxillary sinus- located on pinnacle of ethmoidal bulla
Vomer
Articulations: sphenoid, perpendicular plate of ethmoid, nasal septal cartilage, palatine (horizontal portion), palatal shelves of the maxilla.
Foramina- assists in forming CHOANAE with the sphenoid and palatine bones.
Inferior concha
located on the lateral nasal wall inferior to the middle concha; exists as its own bone.
Articulations: maxilla, vertical portion of palatine bone
Mandible
Articulation- forms temperomandibular joint (TMJ) with mandibular fossa
Landmarks
Ramus- vertical portion of mandible
Angle- oblique angle located between ramus and body
Body- portion distal to angle
Condyle (head) - rounded eminence that completes TMJ
Neck- transition area from ramus to condyle
Mandibular notch- located superiorly on the ramus between the condyle and coronoid process
Coronid process- sharply rounded area anterior to the mandibular notch
Oblique line- anterior sloping line inferior to coronid process leading from ramus to body
Retromolar trigone- triangularly shaped area posterior to 3rd molar
Lingula- pointed process located on medial ramus inferior to coronid process
Mandibular foramen- opening to inferior alveolar canal located directly posterior to the lingual; communicates with the mental foramen
Mylohyoid groove- groove on medial portion of ramus beginning at the mandibular foramen angling anteriorly and inferiorly
Mylohyoid line- elevation on the medial side of the body of the mandible made by the attachment of the mylohyoid muscle
Mental spines (genial tubercles)- 2 pairs of spines located on the lingual side of the mental symphysis (where the 2 developing portions of the mandible fused) for the purpose of attachment of the geniohyoid muscles
Mental foramen- opening of the mandibular canal on the lateral surface of hte mandible opposite the second bicuspid
Ramus
- vertical portion of mandible
Angle-
oblique angle located between ramus and body
Body-
portion distal to angle
Condyle (head) of mandible
rounded eminence that completes TMJ
Neck of mandible
transition area from ramus to condyle
Mandibular notch
located superiorly on the ramus between the condyle and coronoid process
Coronid process-
sharply rounded area anterior to the mandibular notch
Oblique line of maxilla
anterior sloping line inferior to coronid process leading from ramus to body
Retromolar trigone-
triangularly shaped area posterior to 3rd molar
Lingula-
pointed process located on medial ramus inferior to coronid process
Mandibular foramen-
opening to inferior alveolar canal located directly posterior to the lingual; communicates with the mental foramen
Mylohyoid groove-
groove on medial portion of ramus beginning at the mandibular foramen angling anteriorly and inferiorly
Mylohyoid line-
elevation on the medial side of the body of the mandible made by the attachment of the mylohyoid muscle
Mental spines (genial tubercles)-
2 pairs of spines located on the lingual side of the mental symphysis (where the 2 developing portions of the mandible fused) for the purpose of attachment of the geniohyoid muscles
Mental foramen-
opening of the mandibular canal on the lateral surface of hte mandible opposite the second bicuspid
Orbit articulations
frontal, maxilla, zygomatic, lacrimal, ethmoid, sphenoid, palatine
Orbit landmarks
supraorbital notch or foramen (frontal)
anterior and posterior lacrimal crests (maxilla and lacrimal, respectively)
nasolacrimal groove/ fossa
Anterior and posterior ethmoidal foramina
optic canal (sphenoid)
superior orbital fissure (sphenoid)
inferior orbital fissure (between greater wing of sphenoid and maxilla)
Infraorbital sulcus and canal (macxilla)
Nasal cavity
Piriform aperture- nasal opening formed by portions of the nasal bones proper and the maxilla Medial nasal wall a. Nasal septum Lateral nasal wall Sphenopalatine foramen Choanae
Medial nasal wall
Nasal septum-Perpendicular plate of the ethmoid
Vomer
Nasal septal cartilage
Lateral nasal wall
superior and middle nasal conchae (ethmoid)
Inferior nasal concha
- nasolacrimal foramen: located beneath inferior concha, opening for nasolacrimal duct
Sphenopalatine foramen- communication between pterygopalatine fossa and nasal cavity
Choanae or posterior nasal aperture- communication between nasal cavity and nasopharynx.
Infratemporal fossa
area deep to the mandible and inferior to the zygomatic arch
Osseous elements of infratemporal fossa
a. Infratemporal portion of sphenoid
- infratemporal crest- demarcation between temporal surface above and the infratemporal portion below
- lateral pterygoid plate
- foramen ovale
- spine of hte sphenoid
- foramen spinosum
b. Maxilla (lateral surface)
- tuberosity
c. Palatine
- pyramidal process
Landmarks related to the pterygopalatine fossa
a. Sphenomaxillary FISSURE (door)- inverted “tear drop” shaped opening between the lateral pterygoid plate adn the posterior portion of the maxilla
b. Pterygopalatine FOSSA (room)- area inside sphenomaxillary fissure; bounded by teh pterygoid portion of teh sphenoid, the posterior surface of the maxilla and the vertical portion of the palatine bone
c. Sphenopalatine FORAMEN (window)- opening through the junction of the sphenoid and palatine bone communication from teh pterygopalatine fossa to the nasal cavity
d. Posterior opening of inferior orbital fissure.
