Osteology Flashcards
What are the major bones of the neck?
Cervical vertebrae
How many vertebrae are cervical?
7
What is C1 known as?
Atlas
What is C2 known as?
Axis
What are three distinctive features of cervical vertebrae?
1) Triangular vertebral foramen
2) Bifid spinous process
3) Transverse foramina (holes in transverse processes for vertebral artery, vein and sympathetic nerves)
Which are the atypical cervical vertebrae?
C1, C2, C7
Why is C1 atypical?
No vertebral body
No spinous process
Articular facet for dens
Groove for vertebral artery and C1 spinal nerve on posterior arch
Why is C2 atypical?
Has a dens which extends superiorly from the anterior portion of the vertebra, articulating with the atlas
Why is C7 atypical?
Non bifid spinous process
In which vertebrae does the vertebral artery etc not pass through the transverse foramina?
C7 - artery runs around vertebra, veins and nerves still pass through foramina
C1 - artery runs along the groove for the vertebral artery
What is a Jefferson fracture?
Fracture of C1
Vertical fall onto an extended neck - can compress lateral masses between occipital condyles and the axis, causing them to be driven apart and fracturing one/both of the anterior/posterior arches. Transverse ligament may also be ruptured
In a Jefferson fracture, why is it unlikely that there will be damage tot he spinal cord at the C1 level?
This is because the vertebral foramen is large
What is a Hangman’s fracture?
Fracture of the pars interarticularis - between superior and inferior articular facets of the axis
What is the neurocranium?
Formed by superior aspect of the skull - subdivided into calvarium (roof of skull) and cranial base
What makes up the calvarium?
Frontal, occipital and two parietal bones
What is the cranial base comprised of?
6 bones
Frontal, sphenoid, ethmomid, occipital, parietal and temporal bones
What are the facial bones?
Zygomatic, maxilla, mandible, nasal, lacrimal, inferior nasal conchae, palatine, vomer
What are the zygomatic bones?
Forms the cheek bones of the face, articulating with the frontal, sphenoid, temporal and maxilla bones
What are the lacrimal bones?
They form part of the medial wall of the orbit
What are the nasal bones?
Two slender bones located at the bridge of the nose
Where are the inferior nasal conchae?
Located within the nasal cavity
Where are the palatine bones?
Situated at the rear of the the oral cavity, forming part of the hard palate
What does the vomer form?
Posterior aspect of the nasal septum
What are the sutures of the skull?
Coronal - fuses frontal bone with parietal bones
Sagittal - fuses both parietal bones
Lambdoid - fuses occipital bone with parietal bones
What are the two fontanelles and where are they located?
Frontal fontanelle (located at junction of coronal and sagittal sutures) (Bregma intersection)
Occipital fontanelle (located at junction of the sagittal and lambdoid sutures) (Lambda intersection)
What areas of the skull are natural points of weakness?
1) Pterion - thinnest part of the skull
2) Anterior cranial fossa (depression of skull formed by frontal, ethmoid and sphenoid bones)
3) Middle cranial fossa (depression of skull formed by sphenoid, temporal and parietal bones)
4) Posterior cranial fossa (depression of skull formed by squamous and mastoid temporal bone plus occipital bone
What are the four major types of cranial fracture?
1) Depressed - occur due to direct blow
2) Linear - simple break in the bone traversing full thickness - most common
3) Basal skull - affects base of skull - present with Battle’s sign/Raccoon eye’s
4) Diastatic - fracture that occurs along a suture line causing a widening of the suture
What is Battle’s sign?
Bruising behind ears
What is a cephalohaematoma?
Sub-periosteal haematoma
Bleeding between periosteum and bone, can’t pass suture lines so only bleeds over the shape of the bone and can’t get to brain!
What are fontanelles?
Large areas of unossified membranous gaps bewteen flat bones of calvaria
When do the anterior and posterior fontanelles fuse in early infancy?
Anterior - 18 months to 2 years
Posterior - 1 to 3 months
What is craniosyntosis?
Early fusion of fontanelles and sutures
What can be used to assess intracranial pressure and state of hydration in newborns?
Inspection and gentle palpation of anterior fontanelle
Why is a fracture of the pterion a concern?
The middle meningeal artery which supplies the skull and dura mater travels underneath the pterion. Therefore a fracture of the pterion can injure or lacerate the MMA, causing blood to collect between the dura mater and the skull - extradural haematoma. This could cause an increase an intra-cranial pressure
What are basilar skull fractures prone to causing?
CSF leaks, from nose or ear
What could a pterion fracture cause?
Extradural haemorrhage
What is present lateral to the mental protruberance on the mandible?
Mental foramen - passageway for neurovascular structures
Where is the mandibular foramen?
Internal surface of ramus of mandible
What passes through the mandibular foramen?
Inferior alveolar nerve and inferior alveolar artery
What passes through the mental foramen?
Inferior alveolar nerve (branch of mandibular branch of trigeminal nerve) and inferior alveolar artery
Note that the inferior alveolar nerve becomes the mental nerve that innervates the skin of the lower lip and front of chin when it passes through the mental foramen
