The Skull Flashcards
The skull is composed of several separate bones united at immobile joints called:
Sutures
The connective tissue between the bones:
Sutural ligament
How is the mandible attached to skull?
Via the mobile temporomandibular joint
The bones of the skull can be divided into the bones of the _______ and the ______
Cranium and face
The _____ is the upper part of the cranium, with the _____ as the lower part.
Vault, base
The bones of the skull are made up of external
and internal tables of compact bone separated by a layer of spongy bone called:
diploë
Is the external or internal table more brittle and thinner?
Internal table
Where are the bones of the skull covered?
On the outer and inner surfaces periosteum
Where the bones of the skull meet
Sutures
Bones of the skull following the lines of suture
Sutural bones
There the two parietal bones intersect with the middle of the frontal bone
Bregma
The superior portions of the frontal bone, occiptal bone, and parietal bones
Calvaria
Opening on the back part of the parietal foramen, for parietal emissary vein (which drains into the superior sagittal sinus)
Parietal foramen
Compound bone that forms the base of the cranium, behind the eye, and below the front part of the brain.
Sphenoid bone
Opening for the brain stem
Cranial foramina
The types of fracture to the skull depends on:
Age of the pt
Severity of the blow
Area of skull receiving the trauma
A severe localized blow produces:
A local indentation
Often accompanied by splintering of the bone
Blows to the vault often result in:
A series of linear fractures that radiate out through the thin areas of the bone
What strongly reinforces the base of the skull, and tends to deflect linear fractures?
The petrous parts of the temporal bones and occipital crests
What is the adult skull compared to? What is the young child skull compared to?
Adult - eggshell that has a limited resilience, beyond which it splinters
Child - ping pong ball, a localized blow produces a depression, but no splintering
What is a “pond” fracture?
localized blow produces a depression without splintering in a young child
What is the cranial fossa?
The inferior cavity of the skull.
Anterior, middle, and posterior regions.
Superior border of petrous part of temporal bone separates the posterior and middle
Sphenoidal crest separates the anterior and middle
In fractures of the anterior cranial fossa, what may be damaged?
The cribriform plate of the ethmoid bone
Usually results in tearing of the overlying meninges
Bleeding from the nose, resulting from fracture in the anterior cranial fossa
Epistaxis
Leakage of cerebrospinal fluid into the nose, resulting from fracture of the anterior cranial fossa
Cerebrospinal rhinorrhea
Fracture involving the orbital plate of the frontal bone results in:
Hemorrhage of beneath the conjunctiva and into the orbital cavity, causing exophthalmus
If the frontal sinus is involved in fracture..
Hemorrhage in the nose
Why are fractures in the middle cranial fossa common?
Because its the weakest part of the base of the skull
What is the weakness of the middle cranial fossa caused by?
The numerous foramina and canals, the cavities of the middle ear and sphenoidal sinus
In fractures of the middle cranial fossa, what is common?
Leakage of cerebrospinal fluid and blood from the external auditory meatus
What nerves may be involved in a fracture of the middle cranial fossa?
Cranial nerves VII and VIII, since they pass through the petrous portion of the temporal bone.
Also, III IV and VI
Cranial nerves III, IV, and VI may be damaged if:
The lateral wall of the cavernous sinus is torn.
Blood and CS fluid may leak into the sphenoidal sinus and into the nose.
Following a fracture of the middle cranial fossa
In fractures of the posterior cranial fossa…
Blood may escape into the nape of the neck deep into the postvertebral muscles
Days after a posterior cranial fossa fracture,…
The blood can black between muscles and appear in the posterior triangle, close to the mastoid process.
The mucous membrane of the roof of the nasopharynx may be torn, and blood may escape there.
If the jugular foramen is damaged, following a posterior cranial fossa fracture, what nerves may be damaged?
IX, X, and XI
Why is the hypoglossal nerve (XII) usually spared in a posterior cranial fossa fracture?
Because the walls of the hypoglossal nerve are strong
Signs of facial bone fractures
Deformity
Ocular displacement
Abnormal movement accompanied by crepitation (crunching sounds) and malocclusion (misaligned teeth)
The muscles of the face are thin and weak and therefore:
Cause little displacement of bone fragments.
Exception is a fracture mandible, because the strong muscles of mastication can cause considerable misplacement of the fractured bone
Most common facial fractures?
Involve the nasal bones, zygomatic bone, and mandible
Maxillofacial fractures occur as a result of:
Massive trauma
What happens in a maxillofacial fracture?
There is extensive swelling of the face, midfacial mobility of underlying bone on palpation, malocclusion of the teeth, and possible leakage of cerebrospinal fluid from the nose (cerebrospinal rhinorrhea) due to fracture of the cribriform plate.
What may happen due to orbital wall damage, following a maxillofacial fracture?
Double vision, diplopia
Damage to the infraorbital nerve in fracture of the maxilla can cause:
Anesthesia or parasthesia of the cheek and upper gum
Blood can leak into the maxillary sinus and then leak into the nasal cavity, resulting in epistaxis
Sites of fracture for maxillofacial are classified as:
Le Fort 1 - below nose, across length of mouth
Le Fort 2 - from cheek bones up over top nose to other cheek bone
Le Fort 3 - from temporal side of orbit, in between orbits, to other temporal side of opposite orbit
