Session 2 - Osteology Of Skull And TMJ Flashcards
What are sutures and where are they
List them
Fibrous tough joints that prevent movement and displacement of skull bones
Occur where one bone meets the other
Coronal (intersection between frontal bone and 2 parietal bones)
Long mid lines suture (separates 2 parietal bones)
Lamboid (occipital with parietal)
What is the bregma
Point of intersection where coronal suture intersect sagittal
What is the lambda
Posteriorly
Sag suture intersect lamboid suture
What are the bregma and lambda
Where fontanelles were in skull in infants
Ossify with age
What are fontanelles
Large areas of unossified membranous gaps between flat bones of calvaria
What are the main clinical fontanelles
Anterior: was/is future site of bregma
Posterior: was/is future site of lambda
Why are fontanelles developed, what is there use
Allow for alteration of skull size and shape during childbirth as well as permit growth of infant brain
At what age do the anterior and posterior fontanelles fuse
Ant - 18month to 2 yrs (used more clinically)
Post- 1 to 3 months
What is the early fusion of fontanelles and sutures called
Craniosynostosis ( rare )
Affect shape and brain development cuz skull cant adapt as brain grows
What is the anterior fontanelles clinically used for
Convex in healthy baby
Palpation over spot will give indication of health
Bulge - high pressure (along with other symptoms)
Dip / sunken - dehydrated
What are the layers of the calvaria
Trilaminar arrangement
Compact bone (outer) Spongy bone (diploe) Compact bone (inner)
What is the trilaminar arrangement of the skull useful for
Keeping head light as well as strong
What is periosteum and where is it
Each bone coated in periosteum (outer, edges, and inner)
one will be stuck to outer table and sutures, continues to inner table (side of bone facing brain)
Where does the middle meningeal artery enter in the dura and why is it important
Meningeal - Up against floor then lateral side of skull to supply dura, run between bone itself and periosteal layer
Between periosteal layer and inner bone
Important in fractures, bleeds ( fill space between periosteum and inner table ) and strip away periosteum from inner table
When reaches sutures peristeum is hardly glued so blood cant strip it so it forms extradural haematoma
Describe the structure of the cranial floor
Anterior, middle, and posterior cranial fossae (depressions)
What bones form the floors of the cranial cavity
Frontal bone (curves around and swings back) to form most of anterior cranial floor
Where does the ethmoid bone sits and list its important features
Middle of anterior cranial fossae
Flat bit (prupaform plate with holes ( foramina ) where olfactory nerves pass where they provide sense of smell around nasal cavity
Describe sphenoid bone and it’s glandular housing
What cranial floor cavity it forms
Forms a little part of anterior cranial fossa (mostly middle cranial fossa tho)
A lot of middle cranial fossa
Saddle like depression (sella turcica) where pit sits in middle
Why is the oestrous part of the temporal bone important
Houses your inner ear components
What forms the posterior cranial floor
Occipital?
Foramen magnum in base of this bone (where brainstem become spinal cord)
Why is the foramen magnum important
It is where the brainstem becomes the spinal cord
If a patient hits their head, but there is no presence or a skull fracture, should you be worried about intracranial injury ?
Yes, even in the absence of a skull fracture n intracranial injury can still occur
When a skull fracture does occur that should incr worry about intracranial injury
What are the two types of cranial vault skull injuries
Linear (like cracking an egg) - straight and no bone displacement
Comminuted (many fracture lines) - may be displaced fragments of bone inwards towards brain (depressed via non depressed (aka non displaced)
Why are blows to the sides of head dangerous
Cuz pterion region is thinnest part and underneath is medial meningeal which can be severed causing extradural haemorrhage
What are basilar fractures and signs
Rare
Signs gives indication what part of cranial floor fractured
Fracture of cranial floor
Anterior cranial fossa - bilateral bruising around and in eye
Middle (petrous part of temporal) called battles sign- blood in middle ear cavity
What fracture is rare to break but easily damagable to the skin
Supraorbital ridge (frontal bone) near Side eye
What bones in the face are the most commonly fractured
Nasal, zygomatic, mandible
What is unique about mandibular fractures
If its fractured it one place there will always be another one
What is a zygoma
Forms part of zygomatic arch of cheekbone
What are some conditions commonly associated with the TMJ
TMJ disorder (pain in ear jaw etc)
Dislocation
Arthritis
If pain in ear but ear fine think TMJ
What is the TMJ joint innervated by
Auriculotemporal nerve
Branch of mandibular division of trigeminal
What is the TMJ joint
Articulation between temporal bone and mandible
Why in facial injuries do you use an x ray but for head you use CT
Want to make sure brain is fine in head injuries (lineated commulated etc) , but in facial just concerned about bones
What is unusual about TMJ structure
Synovial hinge joint divided into 2 synovial cavities by disc
Joint stabilised by capsule and 3 extracapsular ligament
Describe the movements of the jaw and what happens in jaw dislocation
Open jaw slightly occurs in inferior joint capsule (rotational action)
Gliding forward action ( open jaw even wider )where condyles slip onto articular tubercle not in front of, is done by superior half of joint cavity
In front of means dislocation has occurred due to pterygoid muscles and jaw locks due to muscle spasms
