Skull Osteology and Radiographic Apperance Flashcards
How many bones are in the skull
How many bones in Neuro and Viscerocranium?
22
Neuro- 8
Viscero- 14
The skull includes the cranium and mandible.
Cranium consists of Viscero and Neurocranium.
What is the cranial cavity?
Space within cranium, which holds the brain
What are the tough, fibrous, serrated joints between the bones of the skull called?
How do they Chang with age?
Sutures, ossify with age
Compare Foramina and Fissures
Foramina- Round ish holes
Fissure- Slit like holes
What are 3 components of the Neurocranium
- Calvaria (“Skull cap or Vault” no lower limit)
- Cranial Floor
- Cranial Cavity
Compare the development of the Calvaria and Cranial Floor
Calvaria- Begin as membranes, undergo IM Ossification
Cranial Floor- Begin as cartilage, undergo Endochondral Ossification
Describe the development of the Viscerocranium
Begin as Membranes or cartilage and ossify
Most structures develop from Pharyngeal Arches
Describe the Tri-lamina arrangement of the layers of the Calvaria
What is the purpose of this arrangement?
- 2 layers of Compact bone (Outer and Inner tables)
- Separated by a layer of Spongy bone, called the Diploe
Provides strength to skull without adding significant weight
Despite the strength of the Calvaria, what can serve blows result in?
- Local depression and splintering of bone
- Linear fractures radiating away from point of injury
In young age the 2 halves of the Frontal Bone fuse together. Sometimes they do not fuse fully, leaving a suture line in the middle.
Name the suture
Metopic suture
When looking at the skull laterally which part of Sphenoid bone can be seen?
What 3 bones can we see that it shares a suture with?
Greater wing of sphenoid
Frontal, Temporal, Parietal
Where is the Coronal Suture?
Between frontal and paired parietal
Where is the Saggital Suture?
Between the 2 paired parietal bones
Where is the Lamboid Suture?
Between Occipital bone and 2 paired parietal bones
What are the Bregma and Lambda?
Bregma: Junction of Sagittal and Coronal sutures
Lambda: Junction of Sagittal and Lamboid sutures
What is significant about the Bregma and Lambda?
Why is this?
Remain membranous in feta skull up to age of 2 in infant’s skull
This allows growth of bones
What are Fontanelles?
Where are they found?
Large areas of unossified, membranous skull
Between flat bones of Calvaria
Name the 2 main Fontanelles in an infant, and state where they are found
Anterior: At site of future Bregma
Posterior: At site of future Lambda
Why are Fontanelles important?
- Skull bones not fully fused, so allows for alteration of skull size and shape during childbirth
- Permits growth of infant’s brain
When do the anterior and posterior Fontanelles fuse in early infancy?
Anterior: 18 to 24 months of age
Posterior: 1-3 months of age
Rarely, the Fontanelles and/ or sutures can fuse early.
What is this called?
What can this result in later in life?
Craniosynostosis, can result in increased developmental disorders due to increased cranial pressure
Describe the how the Anterior Fontanelles is clinically useful when examining newborns and infants
- Slightly convex in a healthy baby
- AF bulges if high intra-cranial pulse
- AF appears sunken if dehydrated
The Perisoteum covers surface of BOTH inner and outer tables of skull bones.
Describe how it covers the inner table
- Strongly adhered to bone surfaces including edges at suture lines
- Continuous through suture and onto inner table of same bone
What and where is the Pterion?
The thinnest part of the Calvaria, lies on lateral aspect of skull
(Superior and posterior aspect of outer surface of greater wing of sphenoid)
