The Skull Flashcards
Functions of the skull?
Enclose and protect brain and special sense organs
Create a specialised environment in which the brain can thrive (cranial cavity)
Attachment of muscle and meninges
What are the three layers of the bones in the cranium?
Outer plate - compact bone
Diploe- reduces the weight
Inner plate - compact bone
What can the cranium be divided into?
Calvaria aka neurocranium which houses the brain - 8 bones
Facial bones - 14
Which bones form the cap of the cranium?
Frontal
Parietal
Occipital
Temporal
What grooves does the parietal bone have?
Grooves of:
- middle meaningeal artery
- sagittal sulcus
- granular pits
- sigmoid sinus
What are the four parts of the occipital bone arranged around?
Foramen magnum
Which bones form the floor of the calvaria? (Aka cranial fossa, cranial base)
Sphenoidal
Ethmoid
Temporal
Features of the sphenoid bone?
Has the sphenoid sinus
Greater and lesser wings
Pterygoid process
Optic groove
What can fracture of the ethmoid bone lead to?
Anosmia (loss of sense of smell)
Features of the temporal bone?
Squamous portion Mastoid process Mandibular fossa Zygomatic process External auditory meatus Styloid process
Features of the ethmoid bone?
Allows passage of olfactory nerve fibres Cribriform plate Crista galli Ethmoid bulla Ethmoid air cells
What do the bones of the cranial base provide articulation for?
C1 (atlas)
Facial bones
Mandible
What can the calvaria be divided into?
Cap and floor of calvaria
Name the bones of the facial skeleton
Zygomatic Lacrimal Nasal Inferior nasal conchae Palatine Vomer Maxillae Mandible Frontal
How do most of the bones develop?
Intramembranous ossification
What are the main sutures in adulthood?
Coronal suture - between frontal and parietals
Saggital - between both parietals
Lambdoid - occipital with parietals
Visualise it!
What are fontanelles?
Incompletely fused suture joints in neonates
Name the fontanelles and the sutures in which they are found
Frontal fontanelle - junction of coronal and saggital
Occipital fontanelle - saggital and lambdoid
Why are sutures helpful in neonates?
They are open so allow for cranial bones to be pushed together during labour
Serrated edges of the bones can temporarily interlock to protect the brain from injury
What can happen if the baby is premature concerning the skull?
Sutures are too wide
Pressure from birthing does not result in interlocking of bones
Chance of brain damage
Signs of a cranial fracture?
CSF draining from ears/nose - base of skull fracture Poor balance Confusion Slurred speech Stiff neck
Where is the pterion found?
What can happen if it is fractured?
Junction between temporal, parietal, frontal and sphenoid bones
Lacerate Middle meningeal artery causing an extradural haematoma
Where are the points of weakness on the skull?
Pterion
Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
Which bones form each of the cranial fossas?
Anterior - depression formed by frontal, ethmoidal and parietal
Middle - depression formed by sphenoid, temporal, parietal
Posterior - squamous, mastoid temporal bone, occipital bone
Depressed fracture:
What is it?
Cause?
Depression of the bone inwards
Usually by a direct blow
What is a linear fracture?
A break traversing the full thickness of the skull
Get radiating (stellate) fracture lines away from point of impact
Most common
Someone presents with bruising behind ears and eyes - what do you suspect?
Basal skull fracture
What is a diastatic fracture?
One that occurs along the suture line which widens the suture
Most commonly seen in children
What is Battle’s sign?
Bruising behind ears
Clinical features of a facial fracture?
Profuse bleeding
Swelling
Deformity
Anaesthesia of the skin
What makes the bones of the skull less easily unlocked?
The edges are serrated
Which bones are most frequently broken in a facial fracture?
Nasal
What can fracture of the cribriform plate lead to?
If it involves the dura mater, leakage of CSF fluid out of the nostrils
Anosmia if it damages CNI
