Lecture 4 - Osteology Flashcards
Neurocranium
Calvaria
Cranial floor
Cranial cavity
Viscerocranium
Facial skeleton
8 bones of the neurocranium
vault bones
Frontal 2 x parietal 2 x temporal Occipital Sphenoid Ethmoid
How are vault bones developed
By intramembranous ossification
How is the cranial floor developed
Endochondrial ossification
What does the viscerocranium develop from?
From the pharyngeal arches 1 and 2 - innervated by the facial and trigeminal nerve
Sutures
Coronal - between the frontal and parietal bones
Sagittal - between the parietal bones
Lamboid - between the parietal and occipital bones
Names of the fontanelles
Bregma
Lambda
What are fontanelles?
Large areas of unossified membranous gaps between the flat bones of the calvaria which enable some mobility
Uses of fontanelles
Allow movement of calvaria during delivery
Allows growth and development of the brain
When do fontanelles fuse
Bregma- 18 months - 2 years
Lambda- 1 - 3 months
Craniosynostosis
Early fusion of the fontanelles
Why is the bregma clinically usefull
Gentle palpation
- If bulging - high intracranial pressure unless vomiting or crying
- If sunken - dehydrated
Trilaminar arrangement of the calvaria bones
Inner and outer table of compact bone
Diploe spongy bone in between
Adaptation of the calvaria bones
Compact inner and outer table - protection as strong
Diploe- light weight
Periosteum
Covers the surface of the inner and outer tables of the calvaria bones
Strongly adhered to sutures
Cranial fossae
Anterior - mostly frontal bone, ethmoid and lesser wing of sphenoid bone
Middle - greater wing of sphenoid and the petrous part of the temporal bone
Posterior - occipital bone
Anterior cranial fossa
Contains the orbital plates
The cribriform plate and formina
Crista galli
Attachment site of the flax cerebri
Middle cranial fossa
Contains the sella turcica Foramen rotundum Foramen ovale Superior orbital fissure Contains the cochlear and semicircular canals
Posterior cranial fossa
Contains the foramen magnum
Linear skull fracture
Fairly straight
No displacement
Comminuted skull fracture
Multiple fracture lines
+/- displacement
Can be depressed in
Fractured pterion
Middle meningeal artery is immediately beneath bone therefore high risk of extra dural haemorrhage
Extra dural haemorrhage
Intracranial
Blood accumulates between the inner table of bone and the periosteal layer of the dura mater
Lucid interval
Lemon shaped - periosteum strongly adhered to sutures
Presentation of basilar skull fractures
Anterior cranial fossa:
- Bi-periorbital ecchymosis
- CSF rhinorrhea
Middle cranial fossa:
- Haemotympanum
- Battle’s sign
- CSF otorrhea
Basilar skull fracture
Fracture through the base of the skull
Bones of the viscerocranium
Zygomatic Maxilla Nasal Mandible Lacrimal
Le fort classification
Fractures to bone of midface:
- seperation of midface from skull base
- Problems with the airways
Cut eyebrow
Supraorbital ridge is very tough therefore doesn’t tend to fracture but skin easily tears
Common fractures of the face
Nasal bone
Zygomatic bone and arch
Mandible - normally fractures in 2 places
TMJ
Synovial hinge joint
Lined by fibrocartilage therefore articular bones do not come into contact with each other
Stabilised by joint capsule and extracapsular ligaments
Innervated by auriculotemporal nerve (branch of Vc)
TMJ conditions
- TMJ disorder - pain around ear, jaw and lateral side of head. Clicking and locking
- Dislocation
- Arthritis
If open mouth wide
Gliding forward action as the mandibular condyle slides onto the articular tubercle
If open mouth slightly
Hinge rotation via the inferior half of the TMJ with the madibular fossa
Muscles that elevate the mandible
Masseter
Temporalis
Medial pterygoid
Muscles that depress the mandible
Lateral pterygoid
Muscles that protrude the mandible
Lateral pterygoid
Medial pterygoid
Muscles that retract the mandible
Posterior fibres if the temporalis
Dislocation of the TMJ
Jaw locks in open position - anterior dislocation of condyle over the articular tubercle
Muscles of mastication keep jaw locked
