S2 L2 Osteology and Radiographic Appearance of the skull Flashcards
Osteology of the Head and Neck:
- 2 separations of the head
- Neurocranium (top)
- Viscerocranium (bottom)
Skull consists of ___ individual bones
Terminology: fossae, canal, foramina, fissures
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These include:
• Shallow depressions or hollows (fossae) • Bony tunnels (canal)
• Holes
• Round-ish = foramina
• Narrow slits = fissures
Bones of the skull can be broadly divided into two groups:
- Name
- What bones make up each part of the skull
Neurocranium (also known as ‘cranium’, but should state neurocranium
- Can be split into 3 (list)
- Why are there ‘holes’ in the _____ _____?
- Recap: What is the cranial v_____ compared to the cranial f_____?
Calvaria (vault)/cranial roof, cranial floor/base, cranial cavity
‘Holes’ in cranial floor permit cranial nerves and blood vessels to enter into and out of neurocranium → Foramina, fissures and canals
- Bones and joints of the Calvaria (vault)
Frontal, occipital, two parietal bones
Clinical correlate: Line in forehead
2 bones fuse to form this frontal bone. If they fail to fuse, can leave a suture called metopic suture (don’t mistake it for a fracture!)
- Calvaria: Name of suture lines
Name of the 2 places where the suture lines meet
2 places suture lines meet:
Anterior fontanelle - fuse and become the bregma
Posterior fontanelle - fuse and become the lambda
- *Clinical correlates: Fontanelles**
- what is this?
- 2 main ones, describe
- Why is it present?
- When do they fuse?
- Why is it clinically useful examining the a_____ frontanelle in newborns and infants? What can this show?
- May be slightly convex shape in a healthy baby!
- Can be used to assess intracranial pressure and state of hydration
… if dehydrated - could be sunken
… if raised intracranial pressure - frontanelle can appear to bulge
- *Clinical correlates: Craniosynostosis**
- what is this?
Early fusion of frontanelles and sutures
Brain doesn’t have enough room to grow
Can be ‘fixed’ in surgery
If not fixed, will develop developmental probelm, due to high pressure in brain
- Bones of the Calvaria:
- What is the ‘make’ up in cross-section (how is the bone arranged?)
- Why is it arranged in this shape?
- *Clinical correlate: What does a extradural intracranial haemorrhage appear like on CT scan?**
- why?
Periosteum shrink-wrapping the bone
Covers the outer and inner table of skull bones, including the edges (wiggly in pic)
It is strongly adhered to bones at suture lines and continous through suture and onto inner table of same bone
So when bleeding occurs between the inner table and periosteum, blood ‘strips’ away the periosteum from the inner table of the bone, but at the edges of the periosteum, it is strongly adhered, so can’t stripe this part of the periosteum away.
- Cranial Floor/base
- How is this divided?
- Seats different parts of the brain…
- Made up of…
Key: Divided into anterior, middle and posterior cranial fossae
- Anterior cranial floor/base
- Bones forming it?
- Floor
Bones forming:
frontal (including the orbital plates that lie over the orbits), ethmoid, superior part of the sphenoid
Floor:
Frontal crest, ethmoid bone (the crista galli), cribriform plate
- More detail about the Ethmoid bone:
- Label most important bits
Ethmoid air cells
Crista galli
Perpendicular plate
Cribriform plate
Cribriform foramina
- More detail about the sphenoid bone
Sella turcica
Lesser wings
Greater wings
Dorum sella
- Middle Cranial Fossa
- Bones
- Contents
- Bones: Sphenoid, 2 Temporal bones
- Contents: Pituitary gland, temporal lobes of the brain
- More information about Temporal bone
- Sections of this bone
- What does this bone ‘house’, which specific part of this bone ‘houses’ this?
The petrous part of the temporal bone houses the middle and inner ear structures
- Posterior Cranial Fossa
- Which bones make it up?
- Contents
Bones: Mastoid part of the temporal bone, the squmous, coundylar and basilar part of the occipital bone
Contents: Brainstem and cerebellum
Other things to point out in this bone: Nuchal line, external occipital proturberance, foramen magnum
- *Clinical correlates: Skull fractures of the neurocranium can involve the cranial vault or cranial floor**
- Why is significant trauma required?
- Risk of injury to which structures?
- *Clinical correlate:**
- Skull fractures can be ___ or ___
- Which are is the most easiest to fracture? and why?
- Relationship between this area and an artery: State which artery, what happens in the injury, why
Middle meningeal artery (lies under the pterion)
Extradural intracranial haemorrhage
- *Clinical correlate: Skull base fractures**
- How common compared to skull vault fractures?
- Signs of orbital plate fracture
- Signs of middle cranial fossa fracture (particularly involving the petrous part of the temporal bone)
- Signs of ethmoid bone fracture
- Signs of orbital plate fracture: Periorbital ecchymosis (bruising around eyes) → Panda eyes. May take hrs or weeks to develop
- Signs of middle cranial fossa fracture: Blood and CSF coming out of ear, bruising behind the ear (Battle’s sign), ear drum with blood pooling in middle ear cavity, CSF coming from nose
- Signs of ethmoid bone fracture: CSF from nose
- Facial skeleton (viscerocranium)
- Name the bones
- How to investigate fractures in viscerocranium compared to neurocranium
Zygomatic, maxilla, nasal, lacrimal, mandible
Facial fractures - first line of imaging is X-ray
All others - first line of imaging is CT
- *Clincal correlates: Facial Injuries and Fractures**
- Which facial fractures are rare?
- Which facial fractures are common?
- How to image mandible fractures (specific type)
Mandible fractures: OPG (orthoparitomigram)
X-ray taken to see the whole view of the mandible
Temporomandibular Joint
- Articulation between…
- Type of joint
- Conditions that can affect it (Clinical correlate)
- Innervated by which nerve?
- Anatomy of the TMJ
- Articulation between temporal bone and mandible (specifically the condyle)
- Synovial hinge-type joint divided into two synovial cavities by fibrocartilaginous disc
- Number of conditions:
– TMJ disorder (pain [often refers to ear, jaw, lateral side of head*], clicking, locking…)
– Dislocation (e.g. secondary to trauma, yawning)
– Arthritis - Innervated by auriculotemporal nerve - Branch of mandibular division of trigeminal (Vc) (this is a sensory nerve that also supplies sensory info from the side of the face, jaw, ear - so may get pain here too
- Anotomy of TMJ - pic
TMJ:
- Movement of the TMJ
- Muscles involved at TMJ: elevation, depression, protrusion, retraction, grinding
- *Clinical correlate:** TMJ dislocation
- What happens in this?
- Where does the jaw lock?
- How to ‘fix’ it
- Facial trauma (blow to side of jaw, especially if open) and yawning can cause TMJ dislocation
- Jaw locks as joint fixes in open position due to anterior dislocation of condyle over the articular tubercle (lies anterior to the tubercle)
- Contraction of muscles around joint (muscles of mastication) keep joint locked in anterior displacement
- Reduction
More detail on osteology:
- Frontal bone: Identify the orbital plates
- Ethmoid bone: Identify the crista galli, cribriform plate and cribriform foramina
Left - Frontal bone
Right - Ethmoid bone
More detail on osteology:
Sphenoid bone: Identify Body, lesser and greater wings, Clinoid processes, dorsum sellae, sella turcica, pituitary fossa
pic
More detail on osteology:
Identify the following ‘holes’ and what goes through them
“R O L S” can help: foramen- rotundum, ovale, lacerum and spinosum.
Note the ‘shape’ of these foramina, for the most part, give you a clue to which is which! For the most part the gaps/holes are within the shape of the sphenoid bone (yellow in the image below) or are formed by small gaps between the sphenoid and temporal bone (brown in the image below)
- Superior orbital fissure- transmits lots of different nerves (include Va); communicates with orbit
- Optic canal- transmits the optic nerve
- Foramen rotundum- transmits maxillary division of the trigeminal nerve (Vb)
- Foramen ovale- transmits mandibular division of the trigeminal nerve (Vc)
- Foramen lacerum-in life, filled with cartilage; internal carotid a. traverses over the top of it during its course, just after emerging from the carotid canal
- Foramen spinosum- transmits middle meningeal artery
- Carotid canal- transmits the internal carotid artery (don’t confuse this with foramen lacerum…)
More detail on osteology:
Temporal bone:
- Petrous part (seen looking inside the skull; ‘chunky’ and its ‘ridge’ delineates boundary between middle and posterior fossae)
- Internal auditory meatus (a hole in the petrous part, seen looking inside the skull)
- Stylomastoid foramen (look from underneath: clue for its location is in its name…what it’s found between)
- Styloid process (look from underneath- sharp downward projection)
More detail on osteology:
Occipital bone:
• Foramen magnum (the big hole!)
• Hypoglossal canal
• Jugular foramen*
*lies between petrous part of temporal bone and occipital bone
More detail on osteology:
Mandible -
Body, Ramus, Angle, Coronoid process, Condylar process (head and neck of mandible), mental protuberance, mental foramen, mandibular foreamen
pic
