AH&N- Bones Of The Skull Flashcards
How can the bones of the neurocranium be divided?
Calvarium (roof): frontal, occipital and parietal bones
Cranial base: frontal, sphenoid, ethmoid, occipital, parietal and temporal bones
Which bones comprise the viscerocranium? And what do they articulate with?
14 bones
Zygomatic (2)- cheek bones-articulate with frontal, sphenoid, temporal & maxilla
Lacrimal (2)- smallest bones. Medial wall of orbit.
Nasal (2)- bridge of nose.
Inferior nasal conchae (2)- increase SA of nasal cavity so more inspired air comes into contact with cavity walls.
Palatine (2)- rear of oral cavity& part of hard palate.
Maxilla (2)- part of upper jaw & hard palate.
Vomer- posterior aspect of nasal septum.
Mandible- temporomandibular joint with cranium.
What is the clinical importance of sutures?
Potential points of weakness.
What are the sutures of the skull?
Coronal suture: fuses frontal bone & 2 parietal bones
Sagittal suture: fuses both parietal bones together
Lambdoid suture: fuses occipital bone to 2 parietal bones
What are the sutures called in neonates?
Incompletely fused structure joints give rise to membranous gaps between the bones known as fontanelles.
What are the two major fontanelles?
Frontal fontanelle: junction between coronal and saggital sutures
Occipital fontanelle: junction between saggital and lambdoid
What are the areas of weakness for a cranial fracture?
Pterion: H-shaped junction between temporal, parietal, frontal and sphenoid. Thinnest part of skull. Fracture can lacerate middle meningeal artery causing extradural haematoma.
Anterior cranial fossa: formed by frontal, ethmoid & sphenoid
Middle cranial fossa: formed by sphenoid,temporal & parietal
Posterior cranial fossa: formed by squamous & mastoid temporal bone & occipital
What are the four types of fractures?
Depressed: fracture + depression of bone inwards- direct blow
Linear: simple break across full thickness. Radiating fracture lines from impact, most common type.
Basal: affects base of skull- bruising behind ears (battles sign, mastoid ecchymosis) or bruising around eyes (racooneyes)
Diastatic: fracture along suture, widen suture, most in children
What are the symptoms for a cranial fracture?
Bleeding, poor balance, confusion, slurred speech, stiff neck, clear fluid draining from ears and nose (cerebrospinal fluid).
What are the common causes of facial fractures?
Road traffic collisions, fights and falls.
What are the bones involved in facial fractures?
Nasal bones
Maxillofacial
How can maxillary bone fractures be identified?
Le Fort classification- depending on bones involved, ranging 1-3
What are the five parts of the temporal bone?
Squamous Zygomatic process Petromastoid Tympanic Styloid process
What does a fracture of the Pterion cause?
Skull is weakest
Lacerate middle meningeal artery
Blood collects between dura mater and skull causing a dangerous increase in intracranial pressure- extradural haematoma
Causes nausea, vomiting, seizures, bradycardia & limb weakness
Treated by diuretics in minor cases and drilling burr holes into the skull in extreme haemorrhages
What is mastoiditis?
Middle ear infection (otitis media) can spread to mastoid air cells, due to porous nature suitable for pathogenic replication.
The mastoid process itself can get infected and can spread to middle cranial fossa & into brain causing meningitis.
If mastoiditis is suspected pus may be drained from the air cells- care must be taken not to damage facial nerve.
