Osteology of the Head Flashcards
Identify the main neurocranium bones of the skull
Look at onenote
Neurocranium vs viscerocranium location
- Neurocranium encase and protect the brain
- Viscerocranium are the facial skeleton and jaw
What are the 3 components of the neurocranium
Calvaria, cranial floor, cranial cavity
State the difference in development between calvaria and cranial floor
- Calvaria bones begin as membrane (intramembranous ossification)
- Cranial floor bones begins as cartilage (endochondral ossification)
Describe the cranial floor structure
- 3 bowl shaped depressions form the cranial floor
- Anterior cranial fossae higher than middle which is higher than posterior cranial fossae
- Each fossae has series of foramina, some have fissures and canals
- Allow communication with other areas of the head and neck
- Bone grooved by location of dural venous sinuses
State the components of the trilaminar arrangement of calvaria and describe its purpose
- Trilaminar arrangement confers protective strength without adding significant weight
- Inner and outer table made of compact bone
- Diploeic cavity made of spongy tissue surrounded by compact bone from outer and inner table
What are sutures
- Fibrous joints called sutures exist between bones
- Sutures are intersections between bones of skull
What is the purpose of sutures
- Edges of bones forming suture joint are ‘serrated’ to prevent slippage and movement
- They stop growing in puberty and ossification occurs over time
- Gradually disappear from inside to outside
How is the periosteum and sutures related
- Periosteum covers surface of outer table of bone
- Strongly adhere at suture line but continuous through to periosteum covering inner table
Identify the features of the skull listed on onenote
Good luck
State the sutures on a skull
- Coronal
- Sagittal
- Lamboid
State the sutural intersections and their locations
- Bregma - anterior fontanelle
- Lambda - posterior fontanelle
Describe cephalohaematoma
- Sub-periosteal
- Bleeding from periosteum and bone
- Sheering/torsion injury
- Only bleed in shape of bone - cannot pass through suture lines
- Cannot bleed intracranially
Describe subgaleal haematoma
- Sub-aponeurotic
- Above periosteum
- Bleeding not limited
What is the major risk of intracranial injury
Injury to brain, blood vessels, cranial nerves
What investigation should be performed on suspected skull fracture patients
- CT scan should be performed in all patients with known or suspected skull fractures to identify intracranial injuries
- X-ray only examines skull, not brain
Describe the two main fracture types of skull
- Linear - pass full thickness of skull, straight, no bone displacement
- Depressed - fragment displaced inwards towards brain
What are the consequences of basilar skull fractures
- Associated with cranial nerve injuries
- Nerves that run through foramina most vulnerable
- Prone to causing cerebrospinal fluid leaks
- Blood escapes from skull and accumulates
- Can cause haematoma, haemotympanum (blood behind ear lobe), Racoon eyes (black eye), battle’s sign (bruising over mastoid process)
What is the link between pterion and skull fractures
- Thinnest area of skull and easy to fracture
- Middle meningeal artery passes underneath pterion
- Blows to side of head can fracture at pterion
Why are facial injuries and fractures less common
- Supraorbital ridge and supra ciliary arch very tough - injury normally involves cut to eyebrow
- Fractures of nasal bones, zygomatic bone and arch and mandible are common
What are fontanelles
Large areas of unossified membranous gaps between flat bones of calvaria
What is the purpose of fontanelles
- Allow for alteration of the skull size and shape during childbirth
- Permit growth of infant brain
When do fontanelles fuse
- Anterior: 18 months - 2 years to become bregma
- Posterior: 1-3 months to become lambda
What is it called when fontanelles fuse early
Craniosyntosis
