Lec 4- Osteology and Radiographic Appearance of the Skull Flashcards
(45 cards)
What can the skull be split into?
The cranium and mandible.
What can the cranium be subdivided into?
The neurocranium - those bones forming a protective box around the brain.
The viscerocranium - those bones forming the facial skeleton.
What is the cranial cavity?
This is the space within the cranium, which holds the brain.
What does the neurocranium consist of?
- The Calvaria - skull or cranial cap or roof of the cranium, with no lower limit to it as such.
- The Cranial floor
- May also include the cranial cavity.
Describe the structure of the Calvaria and how it relates to function?
- the bones of the calvaria consist of two layers of compact bone that are separated by a layer of spongy bone, called the dipole.
- This tri-lamina arrangement of compact and spongy bone conveys protective strength to the skull without adding significant weight.
What can severe blows to the neurocranium result in?
- may result in local depression and splintering of the bone or a series of linear fractures radiating away from the initial point of injury.
Why is the pterion an area of clinical importance?
- A fracture at the pterion will injure the middle meningeal artery (its anterior branch) which lies immediately beneath the bone.
What is the pterion?
It is the thinnest part of the calvaria.
It lies on the lateral aspect of the skull.
What does bleeding from the anterior branch of the middle meningeal artery result in?
It causes an extradural haematoma, with blood accumulating between the periosteal layer of the dura mater and the bone.
- the growing haematoma exerts pressure on the underlying brain.
What lies between the large flat bones that form the calvaria and function?
serrated, immobile joints known as sutures (coronal, sagittal and lambdoid)
- The interlocking nature of these joints make it very difficult for the bones forming the joint to dislocate.
- as we age these suture lines begin to ossify.
How is the cranial floor divided?
Into three areas/fossae:
anterior
middle
posterior
What are the bones forming the cranial floor?
- frontal
- ethmoid (in between the frontal)
- sphenoid
- temporal
- parietal (round the circumference)
- Occipital
What do the foramina (holes) in the cranial floor allow?
allows a passage for anatomical structures such as cranial nerves and blood vessels between extra- and intra- cranial compartments.
What is an important thing to do when a patient presents with a head injury?
- It is important to examine the head and wounds thoroughly and undertake a neurological assessment to determine whether there is evidence of or risk for brain injury.
- When there is clinical suspicion of intracranial haemorrhage or brain injury secondary to head trauma, CT imaging of the head will be necessary.
- If there has been significant injury to the head consideration must also be given to the possibility of injury to the cervical spine.
What is a basilar skull fracture?
- fracture through the cranial floor as a result of force being transmitted to the skull base through the vertebral column.
What indicates the presence of a basilar skull fracture?
The presence of: Battle's sign- bruising over the mastoid process Raccoon eyes - bruising around both eyes Haemotympanum - blood behind the eardrum cerebrospinal fluid (CSF) -----leak from the nose (CSF rhinorrhea) -----leak from the ear (CSF otorrheoa)
What is the facial skeleton/ viscerocranium formed of?
It is formed by bones enclosing the orbits, nasal cavity, oral cavity, paranasal sinuses and include the maxillae (upper jaw) and the mandible (the Lower jaw).
What are the main features of the anterior aspect of the skull?
the frontal and zygomatic bones. the orbits nasal region maxillae mandible
What does the frontal bone do?
- It forms the skeleton of the forehead
- It articulates with the lacrimal, ethmoid and sphenoid bones.
- It forms the roof of the orbit and part of the floor of the cranial cavity.
What is the supraciliary arch?
It is a sharp bony ridge just above the orbital margin.
The skin overlying this area can be easily split when there is a blunt force injury to this area of the head.
-The skin over the eyebrow splits, the bone is not fractured.
Where does the zygomatic (cheek) bones lie?
They lie on the inferolateral sides of the orbit, which articulate with the frontal, sphenoid, temporal bones and the maxillae.
What do the maxillae do?
they constitute the greater part of the upper facial skeleton, form the upper jaw (which is fixed to the cranial base).
Why is the mandible moveable?
It is moveable because it articulates with the cranial base at the temporomandibular joint (TMJ).
What are the most common facial fractures?
- They involve the nasal bones ( due to the prominence of the nose), zygomatic bone and/ or mandible.