7 Skull and cervical spine: anatomy and imaging Flashcards
What does the skull house?
- brain
- organs of special senses
- upper part of respiratory and GI system
Where are the restricted movment in the skull?
- mandible at TMJ
- atlanto-occipital joint
Function of skull (4)?
1 protects brain, brainstem, cranial nerves and vaculature
2 attachment for muscles
3 framework for head
4 identity as individuals
Types of bones in skull?
- flat and irregular bones
- pneumatised bones
How are flat, smooth bones formed?
intramembranous ossification
How are irregualr bones formed?
endochondral ossification
What are pneumatised bones? examples?
- bones with air spaces (air cells or sinuses)
- frontal, temporal, sphenoid, ethmoid
Function of pneumatised bones (2)?
1 reduce weight
2 add resonance to our voice
What composes the skull?
- neurocranium and viscerocranium
- total of 22 bones in adult
What is neurocranium?
bony case of the brain including cranial meninges with a dome-like roof (calvaria) and floor (cranial base)
What is viscerocranium?
anterior part of skeleton that consists of bones surrounding the oral cavity, nasal cavity and most of the orbit
Bones of the neurocranium (8)?
- frontal
- parietal x2
- occipital
- sphenoid
- temporal x2
- ethmoid
Bones of the viscerocranium (15)?
- (ethmoid)
- palatine x2
- lacrimal x2
- nasal x2
- zygomatic x2
- vomer
- inferior nasal concha x2
- maxilla x2
- mandible
Main features of viscerocranium?
- zygomatic arch
- mandible
- infratemporal fossa
Main features of neurocranium?
- external acoustic meatus
- styloid process
- mastoid process
- temporal fossa
Borders of temporal fossa?
- superior and posterior: superior + inferior temporal lines
- anterior: frontal process of zygomatic bone + zygomatic process of temporal bone
- inferior: infratemporal crest deep to zygomatic arch
- floor: includes pterion
What is pterion?
- H shaped junction of sutures
- frontal, parietal, temporal and greater wing of sphenoid bones
- structurally weak (thin) area of skull
- overlies anterior branch of middle meningeal artery
- vulnerable to injury
- trauma can lead to extradural (epidural) haematoma
- 4cm superior to mipoint of zygomatic arch + 3cm posterior to frontal process of zygomatic bone
What is calvaria?
- 4 flat bones (2x parietal, single frontal + occipital)
- fused by coronal, sagittal + lambdoid sutures
Function of granular foveolae?
arachnoid granulations - return CSF to venous circulation
What are small isalnds of bones that may be seen within a cranial suture called? most common where?
- sutural, accessory or Wormian bones
- most commonly observed in lambdoid sutures
What are sutures?
- structurally: type of fibrous joint
- functionally: limited or no movement (synarthrosis)
What are fontanelles?
- moulding of crnail shape during birth-post-natal growth of brain
- corners of forntal + parietal bones fuse by 18 months (anterior fontanelle not palpable)
- flat bones are seperated by fibrous membranes that fuse in post-natal life (sutures)
Divisions of trigeminal nerve (CN V)?
- supra-orbital notch
- infra-orbital foramen
- mental foramen
Craniometric points?
-naison
-glabella
-pterion
bregma
-vertex
-lambda
-inion
-asterion
What are the paranasal sinuses?
- forntal
- maxillary
Borders of infratemporal fossa?
- laterally: ramus of mandible
- medially: lateral pterygoid plate of sphenoid bone
- anteriorly: posteior aspect of maxilla
- posterior: tympanic plate, mastoid + styloid processes
- superiorly: infratemporal crest of sphenoid bone
- inferiorly: angle of mandible
What is anterior cranial fossa?
- frontal, ethmoid + sphenoid bones
- shallowest part of cranial base
- occupied by frontal lobes
Where do olfactory bulbs (CN I) receive nerve fibres from the nasal cavity?
via foramina of cribiform plate (olfaction)
What can cribiform plate fractures present wiht?
CSF rhinorrhoea
What id middle cranial fossa?
- sphenoid + temporal bones
- occupied by temporal lobes
Where does pituitary gland lie? Surrounded by?
- lies in hypophyseal (pituitary) fossa (deepest part of sella turcica)
- surrounded by 4 clinoid proceses + 2 superior projections (dorsum sellae post. and tuberculum sellae ant.)
What is posteiror crnial fossa?
- sphenoid, occipital + temporal bones
- occupied by cerebellum + brainstem
What is mandible?
- site for muscle attachemnts (muscles of mastication)
- foramina for passage of neurovascular strucutres
- mandibular teeth within alveolar processes
What is the temporomandibular joint (TMJ)?
- glenoid (mandibular) fossa of temporal bone and condylar process of mandible
- modified hinge (atypical) synovial joint
- articular surfaces of bones covered with fibrocartilage
- fibrocartilaginous articular disc separating the joint into superior and inferior articular cavities
- intrisically ‘unstable’ joint
- anterior dislocation most common
TMJ ligaments?
- 2 extrinsic (spehnomandibular + stylomandibular) and 1 intrinsic (lateral)
- connect mandible to cranium
What is sphenomandibular ligament?
primary passive support of mandible
What is lateral ligament?
- strengthens TMJ laterally
- with postglenoid tubercle prevent posterior dilocation
Muscles involved in protrustion of mandible?
- lateral pterygoid
- assisted by medial pterygoid
Muscles invovled in retraction of mandible?
- posteior fibres of temporalis
- deep part of masseter
- geniohyoid
- digastric
Muscles involved in elevation of mandible?
- temporalis
- masseter
- medial pterygoid
Muscles/ forces involved in depression of mandible?
- gravity
- digastric
- geniohyoid
- mylohyoid
Movement which causes protrusion and retraction of mandible?
Gliding movements between temporal bone and articular disc (superior cavity)
Movement which causes elevation and depression of mandible?
Hinge and rotational movements between head of mandible and articular disc (inferior cavity)
When is the TMJ most unstable?
during depression as the condylar processes move anteriorly and lie underneath the articular eminences wiht the mandibular head being vulnerabel to anteror dislocation into the infratemporal fossa
Name the foramina of cranial fossae?
anteior cranial fossa:
-cribiform foramina in cribiform plate
middle cranial fossa:
- optic canals
- superior orbital fissure
- foramen rotundum
- foramen ovale
- foramen spinosum
- foramen lacerum
posteiror cranial fossa:
- foramen magnum
- jugular foramen
- hypoglossal canal
Contents of cribiform foramna in cribiform plate?
axons of olfactory cells in olfactory epithelium that form olfactory nerves
Contents of optic canals?
- optic nerves (CN II)
- opthalmic arteries
Contents of superior orbital fissure?
- opthalmic veins
- opthalmic nerves (CN V)
- CN III, IV, VI
- sympathetic fibres
Contents of foramen rotundum?
maxillary nerve (CN V2)
Contents of foramen ovale?
- mandibular nerve (CN V3)
- accessory meningeal artery
Contents of foramen spinosum?
- middle meningeal artery and vein
- meningeal branch of CN V3
Contents of foramen lacerum?
- deep petrosal nerve
- some meningeal arterial branche and small veins
Contents of foramen magnum?
- medulla and meninges
- vertebral arteries
- CN XI
- dural veins
- anterior and posterior spinal arteries
Contents of jugular foramen?
- CN IX, X and XI
- superior bulb of internal jugular vein
- infeiror petrosal and sigmoid sinuses
- meningeal branches of ascending pharyngeal and occipital arteries
Contents of hypoglossal canal?
hypoglossal nerve (CN XII)
What are the atypical bones in cervical vertebra?
C1, C2
Where do movements occur?
C0-C1: flexion + extension; lateral felxion
C1-C2: rotation; flexion + extension
C3-C7: lateral flexion; rotation
What is the pre-vertebral fascia?
- allows gliding
- extends down to T3
- covers:
(a) floor of posterior triangle
(b) cervical and brachial plexus
(c) 3rd part subclavian artery
Where do vertebral vessels enter?
-enter foramen transversarium:
- C7: vein
- C6: artery
