Session 3 Flashcards
What is the skull
Collective term referring to the complete skeleton of the head
Cranium can be further divided into the
Neurocranium and viscerocranium
What is neurocranium
Bones forming a protective box around the brain
What is visacerocranium
Bones forming the facial skeleton
What is the cranial cavity
Space within the cranium which holds the brain
Neurocranium consists of the
Calvaria (Skull or cranial cap or roof of cranium)
Cranial floor
Bones of the calvaria consist of
2 layers of compact bone separated by a layer of spongy bone known as diploe
What is the arrangement of the calvaria called
Tri-lamina
Tri-lamina arrangement of compact and spongy bone conveys
Protective strength without adding significant weight
What is the orange region
linear skull fracture
What is the red region
Depressed skull fracture
What is the pink region
Comminuted skull fracture
What is the blue region
Pterion
What is the green region
Basilar fracture
Features of the pterion
Lies on lateral aspect of the skull
Thinnest part of calvaria
Weak
Risk of fracture at pterion
Can injury the middle meningeal artery (anterior branch)- bleeding will cause extradural haematoma, exerts pressure on brain
What is extradural haematoma
Blood accumulating between the periosteal layer of the dura mater and the bone
What are between the large flat bones forming the calvaria
Serrated, immobile joints known as sutures (coronal, sagittal and lambdoid)
Features of sutures
Interlocking nature of joints makes it very difficulty for the bones forming the joint to dislocate- as we age they ossify
The cranial floor is divided into
3 depressions or fossae- anterior, middle and posterior
What are blue and orange
Frontal and Occipital
What are purple and yellow
Ethmoid and Sphenoid
What are red and green
Temporal and parietal
What are found within the cranial floor
A number of foramina - allow passage for structures such a cranial nerves and blood vessels
Bleeding within the cranial cavity causes
Intracranial haematoma- can compress and damage the underlying brain tissue
What needs to be done when a patient presents with a head injury
Neurological assessment and CT imaging of head- check for injury or cervical spine is significant injury
What can happen if significant force is transmitted to the skull base through the vertebral column
Fractures can occur through the cranial floor- basilar skull fracture
Least common fracture
Clinical signs of basilar skull fractures
Battle’s sign (bruising over mastoid process)
Raccoon eyes (bruising around both eyes)
Haemotypanum (blood behind ear drum)
CSF rhinorrhea/otorrhoea (CSF from nose or ear)
What is this
Battles sign indicative of basilar skull fracture
What is this
Raccoon eyes (periorbital haematoma) indicative of basilar skull fracture
Significance of supraorbital ridge
Easily split when blunt force injury
What does the frontal bone do
Form skeleton of forehead and forms roof of orbit and part of floor of cranial cavity
Why is the mandible moveable
Articulates with the cranial base at the TMJ
Most common facial fractures involve the
Nasal bones (due to prominence of nose)
Zygomatic or mandible
A hard blow to the lower jaw often results in
Fracture of the neck of mandible and its body
May be associated with TMJ dislocation
Why are fractures to the bones of the mid face particularly concerning
They cause a separation of some or all of the mid face from skull base and can present problems for the airway
How do you classify injuries to the mid face
Le Fort Classification Type 1,2,3
Depending on plane of injury and bones
What is light green and dark green
Nasal and maxilla
What is purple and pink
Mandible and vomer
What is dark blue and light blue
lacrimal and inferior nasal concha
What is red and yellow
Palatine and zygomatic
What is the outermost layer of the meninges
Dura- involved in creating a number of folds/partitions and venous channels (dural venous sinuses)
What are dural venous sinuses
Venous structures formed by the separation of the 2 layers of dura
Where are cerebral veins and what do they do
Run in subarachnoid space
Connect and drain into the dural venous sinuses - drain brain tissue directly
How do cerebral veins connect to dural Venus sinuses
Bridging veins at certain points
Particularly the length of the superior sagittal sinus
What can happen to bridging veins in head injuries
Brain can move a little within CSF, can cause traction on bridging veins, they can snap.
This leads to extravasation of venous blood which fills the plane between the dura and arachnoid (sub dural space)
Gives rise to sub dural haemorrhage
What does periosteum do in skull
Blood vessels sometimes run underneath e.g. middle meningeal
Covers surface of outer and inner table of skull bones- strongly adhered to bone edges at suture line and continuous through suture and onto inner table of same bone
Which bones contribute to the vault of the neurocranium
Frontal, parietal and occipital bones
What houses the structures of the middle and inner ear
Petrous part of the temporal bone
When the middle meningeal artery ruptures, blood accumulates where
Extra-dural haemorrhage- inner table of bone and periosteum
What is a basilar skull fracture
Fracture of bones of cranial floor
Fracture involving which bone is particularly indicated by bleeding in ear drum or ear
Petrous bone
What fracture is indicated by CSF out of nose
Ethmoid bone of anterior cranial fossa
The cribriform plate and cribriform foramina are features of which bone?
Ethmoid
Condyle of mandible lies anterior to
articular tubercle
Act of TMJ rotational movement occurs within the
Inferior joint cavity
Action of gliding movement of TMJ occurs within the
Superior joint cavity
Which division of the trigeminal nerve innervates the muscles of mastication
7th
Which muscle acts to retract the mandible at the TMJ
Temporalis
Conditions related to the TMJ
TMJ disorder (pain often refers to ear, jaw, lateral side of head), clicking, locking
Dislocation (secondary to trauma/yawn)
Arthritis
TMJ type of joint
Synovial hinge-type
TMJ innervation
Auriculotemporal nerve
Branch of mandibular division of trigeminal Vc
Anatomy of TMJ
Articular surfaces of bones lined with fibrocartilage
Do not come into direct contact
Separated by fibrocartilaginous disc
TMJ is divided into
2 synovial line cavities filled with synovial fluid
Stabilised by joint capsule and 3 extracapsular ligaments
What are red green and blue
Mandibular fossa of temporal bone
Fibrocartilaginous disc
Mandibular condyle (head of condyle)
What area is the star and what happens there
Coronoid process- Temporalis muscle inserts
Which joint capsule is responsible for gliding movement
Superior joint capsule
Which joint capsule is responsible for hinge rotational movement
Inferior joint capsule
What happens in gliding forward action
Condyle slides onto articular tubercle
Elevation of TMJ
Masseter, Temporalis, medial pterygoid
Depression of TMJ
Lateral pterygoid, gravity,
platysma and suprahyoids if against resistance
Protrusion of TMJ
Lateral pterygoid, medial pterygoid assist
Retraction of TMJ
Posterior fibres of Temporalis
Grinding of TMJ
Lateral pterygoids laterally deviate mandible
What happens to condyle in normal depression
Does not pass in front of articular process
Wide opening (depression) of mandible requires
Rotation hinge action and gliding forward
Why does jaw lock
Joint fixes in open position due to anterior dislocation of condyle over the articular tubercle
Contraction of muscles around joint (muscles of mastication)
Venous connection between scalp veins and dural venous sinuses
Emissary
