4. Osteology and Radiology of the Skull Flashcards
What is the neurocranium?
The bones that support or protect the brain
What is the viscerocranium?
Bones forming the facial skeleton
How many bones make up the skull?
22 (8 cranial, 14 facial)
What are the 2 parts of the neurocranium and by what method do they ossify?
Calvaria (skull cap) by intramembranous, Cranial floor (base) by endochondral
What are the bones of the calvaria?
Frontal, 2 parietal, 2 temporal, occipital, 2 greater wing of sphenoid
What are he different sutures of the calvaria?
Coronal (between frontal and parietal), Sagittal (between parietal), Lambdoid (between parietal and occipital)
What is the bregma and lambda?
Bregma (Coronal and sagittal sutures meet), Lambda (sagittal and lambdoid sutures meet)
What are fontanelles?
Areas of unossified membrane gaps between bones of calvaria (where the future bregma and labda are)
What is the function of fontanelles?
Allow alteration of the skull size and shape during childbirth. Permit infant brain growth.
At what age do the fontanelles fuse?
Anterior (18 months - 2 years), Posterior (1 - 3 months)
when do sutures fuse?
sutures not completely ossified in children and only ossify in adulthood
What is craniosynostosis?
Early fusion of fontanelles and sutures
What is the clinical significance of the anterior fontanelle when examining newborns and infants?
Inspection and gentle palpation can be used to assess intracranial pressure and state of hydration.
Bulging = raised intracranial pressure, Sunken = dehydrated
What is the trilaminar arrangement of the calvaria bones?
External and internal compact bone and spongy bone in the middle.
What are the compact bone of the calvaria referred to as?
Outer compact bone = outer table and inner compact bone = inner table
what is the advantage of the trilaminar arrangement?
confers protective strength without adding significant weight
What are all the bones of the calvaria covered in?
Periosteum covers surface of outer and inner table of skull bones
Strongly adhered to bone edges at suture line and continuous through suture and onto inner table of same bone
What is the clinical significance of the periosteum?
extradural Haemorrhage - rupture of MMA between periosteum and inner bone cause periosteum to be pulled off the bone. Blood will pool in this pocket. Periosteum at the sutures cannot be pulled away so blood is restricted to the area. - lentiform shape
What are the 3 parts of the cranial floor?
Anterior, middle and posterior cranial fossae
Which bones make up the anterior cranial fossa?
Frontal bone, ethmoid bone, and anterior parts of the body of and the lesser wings of the sphenoid bone
Which bones make up the middle cranial fossa?
the body and greater wing of the sphenoid, and the squamous and petrous parts of the temporal bone.
What is the zygomatic arch?
Cheekbone. Articulation of the zygomatic process of the temporal bone and temporal process of the zygomatic bone.
Which bones make up the posterior cranial fossa?
mastoid part of the temporal bone and the squamous, condylar and basilar parts of the occipital bone.
what does the petrous part of temporal bone house?
middle and inner ear structures
What surface landmarks are present on the external occipital bone?
external occipital protuberance, supreme, superior and inferior nuchal line
What are the 2 types of cranial vault fractures?
Linear (no bone displacement) or comminuted (multiple fracture lines)
What are the 2 types of comminuted fractures?
Depressed (fragements displaced inwards), non- depressed
What vessels has an important relationship with the pterion and what can fracture here cause?
Middle meningeal artery, extra dural haemorrhage
what is the thinnest area of skull?
pterion - really easy to fracture
What are fractures of the skull base called?
Basilar fractures
What are 5 different signs that suggest basilar fracture?
Battle’s sign, Raccoon eyes, haemotympanum, CSF rhinorrhea, CSF otorrheoa, ear bleeding
What is battle’s sign?
Bruising over the mastoid process
What is raccoon eyes?
periorbital bruising - periorbital echymosis - blood pooling that escaped from fracture
What is Haemotympanum?
blood pooling in middle ear cavity
What is CSF rhinorrhea?
Cerebrospinal fluid leak from the nose
What is CSF otorrhea?
Cerebrospinal fluid leak from the ear
what does haemotympanum, battle’s sign, bleeding from ear and CSF otorrhea indicate about the basilar fracture?
indicates middle cranial fossa fracture particularly involving petrous bone - blood leaks into cavities of ear and manifest as bleeding out of external ear or pooling in middle ear.
what does periorbital ecchymosis or css rhinorrhea with head injury indicate?
anterior cranial fossa fracture
rhinorrhea - involving ethmoid bone
periorbital ecchymosis - involving orbital plates
What are the bones of the viscerocranium?
maxillae (2), mandible, zygomatic (2), lacrimal (2), nasal (2)
Which facial bones are most commonly fractured?
Nasal, zygomatic bone and arch, mandible
which facial bone fracture is rare?
maxillae
What is the supraorbital ridge and what type of injury most commonly occurs here?
A prominence of the frontal bone above the eye caused by the projection of the frontal sinuses. Prone to laceration, tearing of the skin.
What is a feature of fractures of the mandible?
usually fractures in 2 places
What type of joint is the temporomandibular joint?
Synovial hinge joint divided into two synovial cavities illed with synovial fluid by fibrocartilaginous disc
name 3 conditions that can affect the TMJ
– TMJ disorder
– Dislocation (e.g. secondary to trauma, yawning)
– Arthritis
What is TMJ disorder?
Condition affecting movement of the jaw. Generally gets better on its own(pain [often refers to ear, jaw, lateral
side of head*], clicking, locking…)
What is the TMJ innervated by?
auriculotemporal nerve
– Branch of mandibular division of trigeminal (Vc)
What lines the surface of articulating bones in the TMJ and what divides the joint?
- Articular surfaces of bones lined with fibrocartilage and do not come into direct contact
- Separated by fibrocartilaginous disc
What stabilises the TMJ?
Capsule and 3 extracapsular ligament
What are the articulating parts of the TMJ?
Head of Mandibular condyle,
Mandibular fossa and articular tubercle of temporal bone
What movements occur at the TMJ for Depression of the mandible (opening jaw)?
1. Hinge (rotational) action • Inferior half of joint cavity 2. Gliding forward action • Condyle slides onto articular tubercle • Superior half of joint cavity
What movements occur at the TMJ for Simple retraction and protraction of mandible
Gliding action at superior joint capsule
which muscles are involved in elevation of mandible at TMJ?
Masseter Temporalis Medial pterygoid
which muscles are involved in depression of mandible at TMJ?
Lateral pterygoid
Gravity
Against resistance- platysma, suprahyoids assist (while infrahyoids stabilise the hyoid bone)
which muscles are involved in protrusion of mandible at TMJ?
Lateral pterygoid Medial pterygoid (assists)
which muscles are involved in retraction of mandible at TMJ?
Posterior fibres of temporalis (inserts into coronoid process of mandible)
which muscles are involved in grinding of mandible at TMJ?
Muscles of two sides working co-operatively (lateral pterygoids laterally deviate mandible)
What occurs in dislocation of the TMJ?
Anterior dislocation of the mandibular condyle over the articular tubercle. Jaw becomes locked in open position.
What do the muscles around the dislocated TMJ do?
Contract, keep joint locked in anterior displacement
what can cause TMJ dislocation?
Facial trauma (blow to side of jaw, especially if open) and yawning can cause TMJ dislocation
What are some features of the frontal bone?
Supraorbital ridge, Supraorbital notch, Oribital plate.
What are some features of the ethmoid bone?
Cribriform plate, crista galli, superior and middle nasal concha, perpendicular plate.
What are the openings of the ethmoid bone?
Cribriform foramina
What are some features of the sphenoid bone?
Body, lesser and greater wings, sells turcica, dorsum sellae, anterior and posterior clinoid processes, pterygoid processes.
What are some openings of the sphenoid bone?
Superior orbital fissure, Optic canal, foramen rotundum, foramen ovale, formamen spinosum.
What nerve travels through the formamen rotundum and what space does it open into?
Maxillary nerve (of trigeminal nerve) open into pterygopalatine space
What nerve travels through the formamen ovale and what space does it open into?
Mandibular nerve (of trigeminal nerve) open into infra temporal space
What are some features of the temporal bone?
Squamous, petrous, mastoid, zygomatic process, tympanic, styloid process, articular fossa for mandible
What are some openings in the temporal bone?
Foramen lacerum, External and internal auditory meatus, carotid canal, stylomastoid foramen
What are some features of the occipital bone?
External occipital protuberance, superior nuchal line, articular condyles for atlas, clivus
What is the clivus?
Posterior to dorsum sellae, a depression the slopes posteriorly. Pons is located here
What are some openings of the occipital bone?
Formane magnum, hypoglossal canal, jugular foramen
What are some features of the mandible?
Body, ramps, angle, coronoid process, condylar process, mental protuberance
What are some openings of the mandible?
mental foramen, mandibular foramen
