L10 - Skull and TMJ Flashcards
What are the two components that the skull can be divided into?
- The cranium
2. The mandible
What is the skull?
- Collective term referring to the complete skeleton of the head
- Made of 22 discrete bones
- Most bones are joined by fibrous joints - sutures
- Has the temporomandibular joint (TMJ); a v special bilateral moveable joint
What are the 3 further components that the cranium can be divided into?
- The calvaria (neurocranium)
- The upper box-like bony construct - Facial skeleton (membranous viscerocranium) - bones ossified by intramembranous ossification
- The lower and anterior part - Skull base (chondrocranium)
- Articulates with the vertebral column
- Inferior margins of the cranium
- Treat as neurocranium for THIS YEAR
What and where is the pterion?
- The region where the frontal, parietal, temporal and sphenoid bones join together
- Located on side of skull, just behind the temple
- Structurally weak here (thinnest part of skull)
- Lies over the anterior division of the middle meningeal artery
- Puncture would lead to subdural bleed
Describe the sutures of the skull and its significance
- Sutures have serrated edges
- Allows them to interlock firmly
- Less likely for them to be easily unlocked by force applied in only one direction
What are some of the basic functions of the skull?
- Encloses and protects
- The brain
- Special sense organs - Creates a specialised environment in which the brain can thrive
- The cranial cavity - Acts as a site for attachment of:
- Muscles
- Meninges (periostal layer of dura mater)
How does the skull achieve its ‘protective’ function?
- Flat bones are dense, therefore strong
- Layers of bone
- 2 plates of compact bone (thick plates)
- Outer plate
- Inner plate
- Compact packing of bone gives it resilience
- 1 middle layer of spongy bone aka the Diploe; helps red weight of the cranium
- Cranium is tri-lamina bony structure
What is the Diploe?
The spongy, cancellous bone separating the inner and outer layers of the cortical bone of the skull
Where is the cranium thickest?
At the occipital and frontal bones
What are the suture lines found on the cranial cap?
- Coronal
- Longitudinal
- Lamboidal
- Bregma (point)
- Lambda (point)
What are the emissary veins?
- They connect the extracranial venous system with the intracranial venous sinuses
- Drains the scalp, through the skull into the larger meningeal veins and dural venous sinuses
- ‘Cooling brain’
- Primary outflow route for venous drainage
What are the 3 fossa in which the cranial fossa can be divided into?
- Anterior fossa
- Middle fossa
- Posterior fossa
What is the importance of the foramina of the cranial floor?
- Lessen the weight of the skull
- Allow for passage of anatomical structures between extra and intra-cranial compartments
What’s a disadvantage of the foramina of the cranial floor?
- Large no. makes the cranial floor weak
- Therefore, the cranial base is liable to fracture in high energy impacts to the head
What are the right and left mandibles joined by?
Right and left mandibles joined by a midline fibrous joint
- The mental symphysis
