Osteology of the Head and Neck Flashcards
Broadly speaking, what 2 areas can the skull be divided into?
- Neurocranium - encases brain
- Viscerocranium- face and jaw
How do the different types of bones of the neurocranium begin?
- vault bones begine as membranes → intramembranous ossification
- cranial floor/ base bones begin as cartilage → endochondrial ossification
What can the neurocranium be divided into?
Calvaria and Cranial Floor
Label the bones of the calvaria
Label the sutres of the Calvaria
What are fontanelles in infants?
Large areas of unossified membranous gaps between flat bones of the calvaria
Why are fontanelles important?
- Allow for alteration of the skull in size and shape during childbirth
- Permits growth of infant brain
At what age to fontanelles fuse?
Anterior - ~ 18 months
Posterior - ~ 1-3 months
What is craniosynotosis?
Early fusion of fontanelles and sutres, can affect the shape of the skull and brain development
Where are fontanelles located?
Anterior- site of future bregma
Posterior- site of future lambda
How is the anterior fontanelle used to examine newborns/infants?
- In a healthy baby will be slightly convex
- slightly bulging = high intracranial pressure
- sunken = sign of dehydration
How are bones of the calvaria arranged in cross section?
Trilaminar arrangement
2 layers of compact bone (outer and inner table) with a layer of spongy bone in between (diploe)
What is the benefit of the trilaminar arrangement of the calvaria?
Confers protective stregnth without adding significant weight
How does periosteum envelope the bones of the skull?
Each individual bone (including its suture lines) are wrapped with periosteum
Label the cranial fossae of cranial floor
Which bones make up the anterior cranial floor?
- Frontal bone (mainly)
- Ethmoid bone
- Sphenoid bone
What part of the cranial floor does the sphenoid bone make up?
Part of both the anterior and middle cranial floor
What is the sella turcica?
A saddle like depression of the sphenoid bone where the pituitary gland sits
Identify the bones of the cranial base
Which part of the temporal bone houses middle and inner ear structures?
The Petrous Bone
Identify the External Occiputal protuberance and the superior nuchal lines of the occipital bone
What is the difference between linear and comminuted fractures of the cranial vault?
- Linear = straight with no bone displacement
-
Comminuted = multiple fracture lines
- may/ may not be displaced inwards (depressed/ non-depressed)
Identify some clinical signs of a basilar skull fracture (fracture of cranial floor)
- Battle’s sign (bruising over mastoid process)
- Raccoon eyes (bruising around both eyes)
- Haemotympanum (blood bheind ear drum)
- CSF leaking from nose or ear
Identify the bones of the facial skeleton
What is most likely to happen in a facial injury to the supraorbital ridge of the face?
Bone is unlikely to fracture as frontal bone is very tough, instead skin is likely to split
Which bones of the base are morst likely to fracture and why?
- Nasal bone
- Zygomatic bone and arch
- Mandible
As they are the most prominent features of the face
What is important to look for on an x-ray of a fractured mandible?
The mandible will always fracture in 2 places
What is the temporomandibular joint and what type of joint is it?
- The joint between the temporal bone and mandible
- TMJ is a hinge joint
- 2 synovial cavities divided by fibrocartilaginous disc
What conditions can affect the temporomandibular joint?
- TMJ disorder (pain, clicking and locking of the jaw)
- Dislocation
- Arthritis
Which nerve innervates the TMJ joint?
The auriculotemporal nerve
(a branch of mandibular division of trigeminal)
Identify the landmarks of the TMJ
What things stabilise the TMJ?
- Joint capsule
- Extracapsular ligaments
Describe the movement of the TMJ in opening the jaw (depressing the mandible)
- Hinge rotation action of inferior half of joint
- Gliding forwards of the condyle onto the articular tubercle
Why is the jaw locked in an open position in jaw dislocation?
Due to the anterior dislocation of the condyle over the articular tubercle
Give the layers of the scalp
- Skin
- Dense connective tissues
- Aponeurosis
- Loose connective tissue
- Periosteum
Which kind of veins run through the loose connective tissue layer of the scaps and into dural venous sinuses?
Emmissary Veins
Why may you get brusing aroud the eyes following injury to the scalp?
- Subaponeurotic blood vessels in loose connective tissue layer can bleed and track along underneath the margins of the aponeurosis
- anterioraly, aponeurosis continues as frontalis muscle which has no bony instertion
- Instead muscle merges with skin and subcut tissues around the orbit so blood can track and collect in orbital tissue and bridge of nose
