Skull Flashcards
The cranium is composed by:
Neurocranium and Viscerocranium
The neurocranium consists of:
Consists of: dome-like roof → “calvaria” + a floor → “cranial base”
Formed by: 4 singular bones (frontal, ethmoid, sphenoid, and occipital) + 2 sets of bilateral pairs (temporal and parietal)
The viscerocranium consists of:
Consists of: bones surrounding the mouth, nose, and most of the orbits
Cranial base consists of: 15 irregular
3 singular bones (mandible, ethmoid, and vomer) + 6 paired bilateral bones (maxilla, inferior nasal concha, zygomatic, palatine, nasal, and lacrimal)
With which bones does the frontal bone articulate with?
- Inferiorly: nasal, zygomatic, lacrimal, maxila, ethmoid, and sphenoid
- Posteriorly: parietal
With which bones do the zygomatic bones articulate with?
- Superiorly: frontal
- Posteriorly: sphenoid, temporal
- Medially: maxilla
With which bones does the maxilla articulate with?
- Superiorly: frontal
- Laterally: zygomatic
- Posteriorly: palatine, ethmoid, sphenoid, lacrimal
- Medially: nasal, vomer
- Inferiorly: superior teeth in maxillary processes, inferior nasal concha
What are the middle concha?
Curved bony plates that arise from the ethmoid and are located in the superior part of the lateral walls of each nasal cavity
What is the nasal septum composed of?
Vomer and perpendicular plate of ethmoid
Where is the mandible located?
Inferior to temporal bones and maxillary teeth
With which bones do the temporal bones articulate with?
- Superiorly: parietal
- Posteriorly: occipital
- Anteriorly: sphenoid, zygomatic
- Inferiorly: mandible
With which bones do the parietal bones articulate with?
- Inferiorly: temporal, sphenoid
- Posteriorly: occipital
- Anteriorly: frontal
What is the coronal suture?
Fibrous association where frontal and parietal bones meet
What is the sagittal suture?
Fibrous association where right and left parietal bones meet
What is the lambdoid suture?
Fibrous association where occipital and parietal bones meet
What is the bregma
Fibrous association where the sagittal and coronal sutures meet
What is the lambda?
Fibrous association where the sagittal and lambdoid sutures meet
With which bones does the occipital bone articulate with?
- Anteriorly: parietal and temporal, and sphenoid
- Inferiorly: atlas
With which bones does the ethmoid bone articulate with?
- Inferiorly: vomer, maxilla and palatine
- Anteriorly: lacrimals, inferior nasal conchae, and nasals
- Posteriorly: sphenoid
- Anteriorly and laterally: frontal
With which bones does the sphenoid articulate with?
- Superiorly: frontal, parietal, ethmoid
- Posteriorly: temporal, occipital
- Anteriorly: palatine, zygomatic
- Inferiorly: vomer
What are the boundaries of the temporal fossa?
- Superiorly and posteriorly: superior and inferior temporal lines
- Anteriorly: zygomatic and frontal
- Laterally: zygomatic arch
- Inferiorly: infratemporal crest
What are the boundaries of the infratemporal fossa?
- Laterally: ramus of mandible
- Medially: lateral pterygoid plate
- Anteriorly: posterior aspect of maxilla
- Posteriorly: tympanic plate and mastoid and styloid processes of temporal
- Superiorly: inferior surface of the greater wing of sphenoid
- Inferiorly: where medial pterygoid muscle attaches to mandible near its angle
The orbits are formed by…
4 walls and 1 apex
- Superior wall: orbital part of frontal; near apex the lesser wing of sphenoid
- Medial wall: ethmoid + contributions of frontal, lacrimal, sphenoid
- Lateral wall: frontal process of zygomatic + greater wing of sphenoid
- Inferior wall: maxillae, partly zygomatic and palatine
- Apex: located at optic canal in lesser wing medial to superior orbital fissure
What is the sella turcica composed of?
- Tuberculum sellae: slight elevation anteriorly of body of sphenoid
- Hypophysial fossa: saddle-like depression in the middle for the pituitary gland
- Dorsum sellae: posteriorly, formed by squared plate on body of sphenoid
What composes the roof and floor of the temporal fossa?
-Floor: part of frontal, parietal, temporal, greater wing of sphenoid
- Roof: formed by the temporalis fascia
Where is the pterion and what is it?
Location: anterior temporal fossa. superior to midpoint of zygomatic arch
Is a fibrous association between frontal, parietal, temporal, and greater wing of sphenoid
Where is the sella turcica?
It composes the central part of the middle cranial fossa on the body of sphenoid; surrounded by anterior and posterior clinoid processes
What is the origin of temporalis muscle?
- Floor of temporal fossa
- Deep surface of temporalis fascia
What is the insertion of temporalis muscle?
- Tip and medial surface of the coronoid process of the mandible
- Anterior border of the ramus of mandible
What is the function of temporalis muscle?
- Elevate the mandible
- Posterior more horizontal fibers are retractors of mandible
What is the nerve supply of the temporalis muscle?
Mandibular (V3)
What is the origin of the masseter?
- Inferior border and medial surface of the maxillary process of the zygomatic
- Zygomatic arch
What is the insertion of the masseter?
- Angle and lateral surface of the ramus of the mandible
What is the nerve supply of the masseter?
Mandibular (V3)
What is the function of the masseter?
- Elevate the mandible
- Superficial fibers make a small contribution to protrusion
What is the origin of the lateral pterygoids?
1) Infratemporal surface and crest of the greater wing of the sphenoid
2) Lateral surface of the lateral pterygoid plate
What is the insertion of the lateral pterygoids?
1) Superior head mainly attached to the joint capsule and articular disc of the TMJ
2) Inferior head to pterygoid fovea of the anteromedial aspect of the neck of the condyloid process of mandible
What is the nerve supply of the lateral pterygoids?
Mandibular (V3)
What is the function of the lateral pterygoids?
- Acting “bilaterally” depress the mandible and protract it
- Acting “unilaterally” swing jaw contralaterally
- Alternating unilaterally produce larger lateral chewing movements
What is the origin of the medial pterygoids
1) Medial surface of lateral pterygoid plate and pyramidal process of palatine
2) Tuberosity of maxilla
What is the insertion of the medial pterygoids?
Medial surface of ramus of mandible, inferior to mandibular foramen
What is the nerve supply of the lateral pterygoids?
Mandibular (V3)
What is the function of the medial pterygoids?
Elevation of mandible by acting synergistically with masseter; contributes to protrusion
Alternate unilateral activity - smaller grinding movements
What type of joint is the TMJ?
Modified hinge type of synovial joint that allows movement in 3 planes, articulate via a fibrocartilaginous disc instead of hyaline cartilage
What is the TMJ composed of?
Condyloid process fits into the mandibular fossa of temporal and the articular tubercle of the temporal
Which types of ligaments are involved in mastication and how many are there?
One intrinsic (lateral ligament) and two extrinsic (“stylomandibular” and “sphenomandibular”)
Compartments of TMJ
Articular disc divides joint cavity into two synovial compartments (superior and inferior)
How does mastication occur?
Movements mainly produced by muscles of mastication
Wider depression
1. Head of mandible + articular disc move anteriorly until head inferior to the articular tubercle: “translation”
Side-to-side chewing
1. Unilateral anterior gliding where the head of retracted side rotates on inferior articular surface
Protrusion and retrusion
1. Mandibular head articular disc slide anteriorly and posteriorly, moving bilaterally on the articular surface of temporal
What is the nasion?
Cephalometric point where the frontal and the nasal bones unite
What is the glabella?
Smooth area between superciliary arches
What is the piriform aperture and which relevant structures can be found on it?
Anterior nasal opening inferior to nasal bones surrounded on its majority by the maxilla
- Structures: vomer, ethmoid, inferior and middle nasal concha
What are the parts that compose the mandible?Describe them
- Head: superoposterior projection of the ramus
- Ramus: vertical part
- Coronoid process: anterior projection from the ramus of the mandible
- Condylar process: projection from the head of mandible, posterior to coronoid process
- Angle: point of union between the body and the ramus
- Body: horizontal part
What is the mastoid process and where is it?
Conical projection; located posteroinferior to external acoustic meatus
What is the styloid process and where is it?
Narrow pointed projection, directed downwards and anteriorly; located inferior to external acoustic meatus
What is the external acoustic meatus and where is it?
Acoustic opening that leads to the tympanic membrane; located between mastoid process of temporal and condylar process of mandible
What is the mandibular fossa, where is it and why is it important?
Oval depression behind anterior root of zygomatic process of temporal
What is the external occipital protuberance and where is it?
Elevation in the median plane of the bone; located on the of inferior part of occipital in the midline
What is the superior nuchal line and where is it?
Extend laterally from each side of the protuberance; located superior to the protuberance
- Form attachments to stabilize atlanto-occipital joint
What is the inferior nuchal line and where is it?
Same as the superior, but runs inferiorly to the protuberance
What are the occipital condyles and where are they?
Paired prominences on the sides of the foramen magnum that articulate with the atlas
What is the foramen magnum and where is it?
Largest opening of the skull, encircled by occipital; spinal cord exits the cranial cavity through this
What is the crista galli and where is it?
Median ridge of bone that projects superiorly from ethmoid; located posterior to foramen cecum of frontal
What are the cribiform plates of the ethmoid and where are they?
Portion of ethmoid on each side of the crista galli
What are the parts of the sphenoid and where are they?
- Body: centrally positioned
- Greater wing: arises posterolaterally from body
- Lesser wing: arise superolaterally from body
- Pterygoid processes (medial and lateral): extend inferiorly on each side of sphenoid from junction of body and greater wings
Where is the infratemporal fossa located?
Location: inferior to zygomatic arch, deep to ramus of mandible, and posterior to maxilla
What is the extension of the temporalis fascia?
Superior nuchal line to the zygomatic arch
What is the function of the temporalis fascia?
Provides resistance to downward pull of masseter on the zygomatic arch
What is the function of the lateral ligament?
Strengthens TMJ laterally, prevents posterior dislocation of joint (along with postglenoid tubercle)
What is the extension and function of the stylomandibular ligament?
Extension: styloid process to angle of the mandible
Function: limit excessive protrusion of jaw
What is the extension and function of sphenomandibular ligament
Extension: spine of sphenoid to lingula of mandible
Function: limits lower distension of mandible
