Osteology And Radiographic Appearance Of The Skull Flashcards
What are the following: Fossae Canals Foramina Fissures
Fossae- shallow depressions
Fissures - narrows slits
Round holes - foramina
Narrow slits- fissures
How many bones make up the neurocranium? What did they develop from?
8 bones
Calvaria (skull cap/ vault) - begin as membranes (intramembranous ossification)
Floor/ base begin as cartilage (endochondrial ossification)
How many bones make up the viscerocranium? What did they develop from?
14 bones
Facial skeleton and jaw
Begin as membranes or cartilage and ossify
Structures mostly develop from the 1st and 2nd pharyngeal arches
What bones make up the neurocranium?
Anterior = frontal
Inferior to frontal and lateral= sphenoid bone
Posterior = parietal
Inferior to parietal= temporal
Most posterior = occipital
What separates the frontal and parietal bones?
Coronal suture
What separates the parietal bones?
Sagittal suture
What separates the parietal bones from the occipital bone?
Lambdoid suture
Where do the coronal suture and Sagittal suture meet? What did this develop from and at what age?
Bregma
In newborn it’s a gap filled with fibrous tissue - anterior fontanelle
Changes from 18months - 2yrs
Where do the Sagittal suture and lambdoid suture meet? What did this develop form and at what age?
Lambda
From the posterior Fontanelle - gap filled with fibrous tissue until 1-3months
What is the function of fontanelles?
Areas of membrane between flat bones of calvaria which allow for alteration of skull size and shape during childbirth
What is craniosynostosis?
Rare condition where there is early fusion of fontanelles and sutures
What can inspection and gentle palpation of the anterior fontanelle tell you about a newborn/ infant?
If bulging can mean ICP is high
If sunken can mean dehydrated
Normal baby should be slightly convex
Used alongside other signs and symptoms
What is the trilaminar arrangement of bones in the calvaria? What’s the purpose of this arrangement?
Compact bone for outer table
Spongy bone = diploe (middle)
Compact bone is inner table
Confers protective strength without adding significant weight
Describe the periosteum arrangement on the calvaria bones. What can occur between the periosteum and dura mater?
Covers the outer table of skull bones, strongly adhered to the edges and continuous through suture and onto inner table of the same bone
(All the way around the bone)
An extradural haemorrhage can occur where a bleed from most commonly the medial meningeal artery strips periosteum from inner table but is too strong to strip the edges of suture so stops
What bone(s) form the anterior cranial floor only?
Frontal bone up to orbital plates
Ethmoid bone (separates nasal cavity from brain) a.k.a Cribriform plate and cribriform foramina
(Sphenoid also)
What bones from the anterior and middle cranial floor?
Sphenoid bone
Anterior: lesser wings
Middle: Lesser and greater wings, Dorsum sella and sella turcica (where pituitary gland sits)
What bones form the middle and posterior cranial fossa?
Temporal bones
Squamous part
Zygomatic process
Mastoid process
Petrous bone
Slide 19
What bone(s) form the posterior cranial floor only?
Occipital bone
External occipital protuberance
Superior nuchal lines
Foramen magnum
Slide 21
2 types of skull cranial vault fractures
Linear- straight, no bone displacement
Comminuted - multiple fractures lines, fragments may displace inwards towards the brain (depressed or non-depressed)
Where is the most likely place to fracture your cranial vault and what structure could this damage?
Pterion- thinnest area of skull
Underlying is middle meningeal artery
Blows to side of head can fracture bone -> intracranial extra-Dural haemorrhage
What is a skull base fracture called and what are some signs this has occurred?
Basilar fracture
Rarer
Raccoon eyes - bilateral periorbital ecchymosis
Battle sign- bruise behind ear
Haemotympanum - Blood in tympanic cavity of middle ear
What bones make up the facial skeleton?
Lateral superior - 2 zygomatic bones
Inferior- mandible
Central - maxilla
Above nose- nasal
Inner eyes- lacrimal
What facial fractures can occur?
Supraorbital ridge of frontal bone (superior orbital fossa) very tough so can splinter skin
Fractures of nasal bones, zygomatic bone and arch, mandible (always fractures at 2 places) are common
Maxillae fracture is rare
What type of joint is the temporomandibular joint?
Synovial hinge joint divided into two synovial cavities by fibrocartilaginous disc
