Skull and cervical spine: anatomy and imaging Flashcards
What is the skull and its function?
The skull is the bony Skelton of the head and is the most complex bony structure in the body
Houses the brain, organs of special sense, upper pars of respiratory & GI system
Function;
- Protects brain, brainstem, cranial nerves & vasculature
- Provides attachment for muscle
- Provides framework fo head
- Gives us our identity as individuals
What movement does the skull do ?
Restricted movement except the temporomandibular joint (TMJ) and the Atlanta-occipital joint
What type of bones makes up the skull?
- Flat and irregular bones
- Pneumatised bones: Bones with air spaces (air cells or sinuses) to reduce weight & add resonance to our voice
What are the divisions of the skull?
Skull; cranium, skeleton of the head including the mandible, composed of the neurocranium & viscerocranium with a total of 22 bones in the adult excluding the ossicles of the ear (28 with ossicles)
What is the Neurocranium ?
Neurocranium - The bony case of the brain including cranial meninges with a Dom-like roof (calvaria/skullca) & a floor (cranial bas/basicranium)
What is the Viscerocranium ?
Viscerocranium (facial skeleton) - Anterior part of cranium that consists of bones surrounding the oral cavity, nasal cavity & most of the orbit
What are the different parts of the neurocranium ?
Frontal, parietal x2, occipital, sphenoid, temporal x2, ethmoid
What are the different parts of the viscerocranium ?
Ethmoid, lacrimal x2, zygomatic x2, maxilla x2, mandible, nasal x2, inferior nasal concha x2, palatine x2, vomer
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What is the zygomatic arch and its relevance?
Bony ridge formed by process of temporal and zygomatic bone the ridge has temporalis muscle deep to it which passes underneath
What is the mastoid process and its relevance?
Bony process where sternocledomastoid is attached to
What is the external acoustic meatus and its relevance?
passageway that leads from the outside of the head to the tympanic membrane, or eardrum membrane, of each ear
Name the bones and sutures of the superior view of the skull (Calvarium)
Frontal, parietal x2 and occipital bone
Coronal suture - separates frontal from 2 parietal bones
Sagittal suture - separates 2 parietal bones
Lambdoid suture - separates parietal and occipital bones
What would you expect to find internally on the Calvarium?
Groove for anterior branch of middle meningeal artery in frontal bone laterally
Granula foveolae - pits on the inner surface of the skull, along the course of the superior sagittal sinus, in which the arachnoidal granulations are lodged which absorb CSF and puts it into the superior sagittal sinus
Groove for superior sagittal sinus
Bregma - Midline is groove which contains a vein like structure which it the superior sagittal sinus which originates from the out of the nose inside and goes to the brain
What would you expect to see posteriorly on the Calvarium?
- External occipital protuberance
- Superior nuchal line (boundary between neck and skull - reference point)
- Interior nuchal line
- Squamous part of occipital bone
What would you expect to see anteriorly on the Calvarium?
Glabella (bump above nose)
Nasion - Where nose stops and frontal bone starts
Piriform aperture -Entrance of nasal and oral cavity
3 Foramina with divisions of Trigerminal Nerve (CN V);
- Supra-orbital notch (formen)
- Infra-orbital foramen
- Mental foramen
What would you expect to see inferiorly on the Calvarium?
- Hard palate
- Choana (Posterior boundary of nasal cavity - passage of nasal cavity and pharynx)
- Pterygoid process
- Medial and lateral plates of pterygoid process
- Carotid canal (For internal carotid artery)
- Jugular foramen (Joint of temporal and occipital bone - internal jugular vein and 3 cranial nerves pass through)
- Foramen magnum (Spinal cord and vertebral arteries pass through)
- Foramen lacerum (greater petrosal nerve and deep petrosal nerve)
- Foramen ovale (For 3rd division of trigeminal)
- Foramen spinosum (Middle meningeal artery)
- Hypoglossal canal (For 12th cranial nerve)
What is the difference between sutures and fontanelles ?
Sutures;
- Structurally, type of fibrous joint
- Functionally, limited or no movement (synarthrosis)
Fontanelles;
- Moulding of cranial shape during birth (cranial bones go on top of each other and reduce size of head so can go through vaginal canal)
- Post-natal growth of brain (accommodates increase in brain size)
- Corners of frontal and parietal bones fuse by 18 months (anterior fontanelle not palpable)
- Flat bones are separated by fibrous membranes that fuse in post-natal life (sutures)
Name the craniometric points and why do we need to know them?
Craniometric points are important anatomical landmarks in radiology and surgery
Craniometric points;
- Asterion
- Inion
- Lambda
- Vertex
- Bregma
- Pterion
- Glabella
- Nasion
Acronym - Amanda is learning vowels because people graduate now
Why is the Pterion important?
As you can feel it with surface anatomy and its 4cm superior to the midpoint of the zygomatic arch and 3cm posterior to the frontal process of zygomatic bone.
Its quite a weak area as is much thinner than rest
Deep to it there is the middle meningeal artery, a branch of maxillary and passes through foramen spinosum, goes up and gives off branches just - any damages to this area can cause fractures which can sever the artery and cause epidural haematoma - common in road accidents
How do fontanelles give us clinical information about our patients?
Increase in superior cranial pressure this will bulge up or if baby is malnourished it will go down - its normal for it to pulsate - never press too hard as it only skin and a little cartilage and a the huge superior sagittal sinus underneath that which you can see pulsate
Name the features you would see in the skull base (interval view)
Fossa;
- Anterior cranial
- Middle cranial
- Posterior cranial
- Sphenoid crest
- Lesser wing of sphenoid bone - boundary
- Superior border of petrous temporal bone
What would you expect to see in the anterior cranial fossa?
- Crista galli (triangular midline process from ethmoid bone)
- Cribiform plate (of ethmoid bone where olfactory nerves pass). Fracturees here can present with CSF rhinorrhoea
- Olfactory bulbs (CN 1) receive nerve fibres from the nasal cavity via the foramina of the cribriform plate (olfaction)
What would you expect to see in the middle cranial fossa?
Hypophyseal (pituitary) fossa (deepest part of sella tuurnica) - The pituitary gland lies in here and is surrounded by 4 clinoid processes and 2 superior projections (dorsum sellae posteriorly and tuberculum sellae anteriorly)
Foramen ovale
Formen rotundum
(Foramen ovale and rotundum - where 2 divisions of trigeminal exit)
Chiasmatic sulcus - Chias means cross over
Optic canal - optic nerve passes
Superior orbital fissure
Foramen spinosum
What would you expect to see in the posterior cranial fossa?
- Clivus
- Internal acoustic meatus
- Jugular foramen
- Formen magnum
What is the function of the mandible and some of its features?
Only moveable bone in the skull!
- The mandible contains foramina for passage of neurovascular structures
- Mandibular teeth within alveolar processes
- Site for muscle attachments (muscles of mastication)
Features;
- Condylar process
- Pterygoid fovea (where 1 of the muscles of mastication is attached to)
- Coronoid process
- Mandibular Foramen (nerves of lower teeth go through)
- Roughning on angle of mandible for attachment of medial pterygoid muscle
What are some features of the temporomandibular joint? (TMJ)
- Glenoid (mandibular) fossa of temporal bone & condylar process of mandible (modified hinge joint which allows for elevation and depression of mouth)
- Articular surfaces of bone covered with fibrocartilage (not hyaline cartilage!)
- Fibrocartilaginous articular disc separates the joint into superior & inferior articular cavities
- Intrinsically ‘unstable’ joint
- Anterior dislocation most common (most common from big bite or trauma)
Features;
- Upper joint cavity
- Articular disc
- Lower joint cavity
What ligaments help the temporomandibular joint to function?
There are 2 extrinsic and 1 intrinsic (lateral) ligaments which connects the mandible to the cranium
Sphenomandibular ligament - Primary passive support of the mandible
Stylomandibular ligament - this and the sphenomandibular ligament together allows the jaw to swing from side to side when grinding food
Lateral ligament - strengthens TMJ laterally and prevents dislocation
What movements does the TMJ do?
Protrusion - Lateral pterygoid assisted by medial pterygoid
Retraction - Posterior fibres of temporalis, deep part of masseter, and geniohyoid and digastric
These 2 movements are both considered as gliding movements between the temporal bone & articular disc (superior cavity)
Elevation - Temporalis, masseter, medial pterygoid
Depression - Gravity and digastric, geniohyoid and mylohyoid muscles
These 2 movements are both considered as hinge & rotational movements between the head of mandible & articular disc (inferior cavity)
What ligaments hold together the Median & lateral Atlanta-axial joints
- Apical ligament
- Alar ligaments
- Transverse ligament of atlas (cruciform)
Keeps dens/odontoid process in this position
If transverse ligament is ruptures then 2 bones would grind and sever spinal cord
What liagments would you find in the normal spine?
- Tectorial membrane
- Anterior longitudinal ligament
- Posterior longitudinal ligament
- Ligament nuchae
