Skull and cervical spine: anatomy and imaging Flashcards
What are the main functions of the skull?
- Protects the brain, brainstem, cranial nerves and vasculature
- Provides attachment for muscles
- Provides a framework for the head
- Gives us our identity as individuals
What are the bones like in the skull?
- Flat and irregular
- Pneumatised (air spaces within bones)
What is the neurocranium?
- Bony base of the brain including cranial meninges with a dome-like roof (calvaria/skullcap) and a floor (cranial base/basicranium)
- In contact with parts of the brain
What is the viscerocranium?
Anterior part of the cranium that consits of bones surrounding the oral cavity, nasal cavity and most of the orbit
WHat are the bones of the neurocranium?
Formed by 8 bones
- Frontal
- Parietal x2
- Occipital
- Sphenoid
- Temporal x2
- Ethmoid
What are the bones of the viscerocranium?
Composed of 15 irregular bones
- Ethmoid
- Palatine x2
- Lacrimal x2
- Nasal x2
- Zygomatic x2
- Vomer
- Inferior nasal concha x2
- Maxilla x2
- Mandible
What bone is in both the viscero and neurocranium?
Ethmoid bone
What is the zygomatic arch formed by?
Zygomatic process of temporal bone and temporal process of zygomatic bone
What make up the temporal fossa?
- Superior and inferior temporal lines
- Supramastoid crest of temporal bone
- Zygomatic arch
Where does the temporalis muscle originate?
Inferior temporal line
Where does the temporal facia attach?
Superior temporal line
Where does the temporalis muscle insert?
- Pass deep to zygomatic arch and insert on coronoid process of mandible
What is the Pterion?
- Important craniometric area
- H shaped junction of sutures where frontal, parietal, temporal and greater wing of sphenoid bone articulate
- Underneath temporalis muscle
- Bones are thin, structurally weak
What artery is vulnerable to injury in the Pterion?
Anterior branch of the middle meningeal artery
Where is the Pterion (surface anatomy)?
4cm superior to midpoint of zygomatic arch and 3cm posterior to frontal process of
What is the calvarium?
Top of neurocranium
- Formed by 4 flat bones
- Parietalx2, Occipital, Frontal
What suture connects the 2 parietal bones?
Sagittal suture
What suture connects the frontal bone to the 2 parietal bones?
Coronal suture
What suture connects the 2 parietal bones to the occipital bone?
Lamboid suture
What is the bregma?
On the calvarium where the coronal suture is intersected perpendicularly by the sagittal suture. Where ant. fontanelle was located
What is the purpose of the groove in sagittal suture?
For the sagittal sinus - carries venous blood to systemic circulation
What is the purpose of the granular foveolae?
Inside are arachnoid granulations
- function is to absorb CSF from the subarachnoid space and pass it on to the superior sagittal sinus
What is the lambda?
Midline bony landmark where the lambdoid sutures and sagittal suture meet, between the occipital and two parietal bones
What is the boundry between the squamous and the nuchal part of the occipital bone called?
Superior nuchal line
WHy is the nuchal part of the occipital bone rough?
For attachment of deep neck muscles and superficial back muscles
Where is the inion located?
- Tip of the external occipital protuberance
- Midpoint of superior nuchal line
What are sutures?
Types of fibrous joints - do not move (or limited) (synarthrosis)
What are the soft spots on the cranium called?
- Anterior fontanelle
- Posterior fontanelle
When does the anterior fontanelle fuse?
18 months
What is the suture between the 2 frontal bones which eventually fuse together called?
Metopic suture
What do unfused sutures allow for?
Brain to grow without being compressed
When does the posterior fontanelle fuse?
6-9 months after birth
What happens to the bones of the neurocranium during birth?
They go over each other
The impression on the anterior fontanelle is useful for what reason?
no bone to protect brain - this protects instead (if depressed infant may be malnourished)
What will make the anterior fontanelle buldge?
Increased intracranial pressure
What are the 3 divisions of the trigeminal nerve?
V1- Opthalmic (sensory)
V2 - Maxillary (sensory)
V3 - Mandibular (sensory + motor)
What is the piriform aperture?
Anterior opening of the nasal cavity (looks like a pear)
What does the opthalmic nerve pass through?
Supra-orbital notch (foramen)
What does the maxillary nerve pass through?
Infra-orbital foramen
What does the mandibular nerve pass through?
Mental foramen
Where is the glabella?
Area between the eyebrows
Where is the nasion?
Point where frontal and nasal bones unite
What travels through the superior orbital fissure?
- Lacrimal nerve
- Frontal nerve
- Trochlear nerve
- Superior opthalmic vein
- Nasociliary nerve
- Oculomotor nerve
- Abducens nerve
What does the superior orbital fissure connect?
The orbit to the middle cranial fossa
What travels through the inferior orbital fissure?
- Zygomatic branch of maxillary nerve
- Infraorbital nerve
- Inferior opthalmic vein
- Sympathetic nerves
What does the inferior orbital fissure connect?
Orbit to pterygopalatine fossa
Where is the vertex located?
Highest most point of the skull
What is the asterion?
Where occipital, parietal and temporal bones unite/join
What is the choana?
Posterior opening of the nasal cavity
What is the sphenoid bone said to resemble?
a bat with the legs representing the pterygoid process
Where does the internal carotid artery enter the cranium?
External opening of carotid canal (on temporal bone)
What is the jugular foramen formed by?
Articulation of the temporal and occipital bones
What foramen does the spinal cord pass through?
Foramen magnum
What does the Hypoglossal nerve travel through?
Hypoglossal canal
What does the middle meningeal artery enter into the cranial cavity through?
Foramen spinosum
What nerve passes through the foramen ovale?
Mandibular
What pases through the foramen lacerum?
Artery of pterygoid canal, the nerve of pterygoid canal and some venous drainage
What are the boundries of the infratemporal fossa?
- Laterally: Ramus of mandible
- Medially: Lateral pterygoid plate of sphenoid bone
- Anteriorly: Posterior aspect of maxilla
- Posteriorly: Tympanic plate, mastoid and styloid processes
- Superiorly: Infratemporal crest of sphenoid bone
- Inferiorly: Angle of the mandible
WHat is the boundry between the infratemporal and temporal fossa?
Zygomatic arch
What is the pterygopalatine fossa?
Narrow space between the pterygoid process of the sphenoid and the palatine bone
What is the connection/door between pterygopalatine fossa and infratemporal fossa called?
Pterygomaxillary fissure
What does the sphenopalatine foramen connect?
Pterygopalatine fossa with nasal cavity
What does the inferior orbital fissure connect?
Pterygopalatine fossa with orbit
What does the foramen rotundum connect?
Pterygopalatine fossa with middle cranial fossa
What are the 3 fossae of the cranial base?
- Anterior middle and posterior cranial fossa
What is the border between the anterior and middle cranial fossa called?
Sphenoid crest
What is the border between the middle and posterior cranial fossa called?
Superior border of the petrous temporal bone
What bones form the anterior cranial fossa?
Frontal, ethmoid and sphenoid bones
Where do the olfactory bulbs receive fibres from?
The nasal cavity via the foramina of the cribriform plate (olfaction)
What can cribiform plate fractures result in?
CSF rhinorrhoea
What is the middle cranial fossa formed by?
Sphenoid and temporal bones and occupied by temporal lobes of the brain
Where is the pituitary gland located?
Hypophyseal fossa
What is immediately anterior to the hypophyseal fossa?
Chiasmatic sulcus (where optic chiasm is located)
What is the posterior cranial fossa formed by?
- Sphenoid
- Occipital
- Temporal bones
What occupies the posterior cranial fossa?
- Cerebellum inferiorly (cerebellar fossa)
- Occipital lobes (cerebral fossa)
What does the brainstem lie against in the posterior cranial fossa?
Clivus
What exit/enter through the internal acoustic meatus (part of posterior cranial fossa)?
Vestibulocochlear + fascial nerve
What passes through the mandibular foramen?
Branch of mandibular nerve supplying the lower teeth gums
What is the only synovial moveable joint in the skull?
Temporomandibular joint (hinge joint)
What are the articular surfaces of the mandible bone covered by?
fibrocartilage (not hyaline)
What seperates the temporomandibular joint into superior and inferior articular cavities?
Fibrocartilaginous articular disc
What is the most common form of dislocation of the temporomandibular joint?
Anterior
What are the ligaments of the temporomandibular joint?
- Sphenomandibular ligament (extrinsic)
- Stylomandibular ligament (extrinsic)
- Lateral ligament (intrinsic)
In what cavity of the TMJ does the mandible retract and protrude?
Superior cavity
In what cavity of the TMJ does the mandible elevate and depress?
Inferior cavity
What is C1 called?
Atlas
What is unique about the atlas?
- No body
- No spinous process just tubercle
- 2 lateral masses with articular surfaces superiorly and inferiorly
What is unique about the axis (C2)?
- Has a dens (articulates on the articular facet on C1)
- 2 lateral masses
What is unique to the cervical vertebra?
Bifid spinous process
What do Occipital condyles articulate with?
Superior articular surfaces on the lateral masses of the atlas
Describe the intervertebral joints
- Secondary cartilaginous
- Hyaline cartilage on endplates
- Intervertebral disc - fibrous
What are the intervertebral joints supported by?
- Anterior longitudinal ligament
- Posterior longitudinal ligament; pierced by vertebral artery; continues cranially as tectorial membrane
Where does the nucleus pulposus herniate?
Posterolaterally (due to presence of ligaments)
- touches spinal nerves
What is another name for the facet joints?
Zygapophysial joints
Describe the facet joints?
- Synovial joint
- Between superior and inferior articular processes
- Hyaline cartilage
- Supported by ligamentum flavum
What ligaments stabilise the atlanto-axial joint?
- Apical ligament
- Alar ligament
- Transverse ligament of atlas (cruciform)
What is the ligamentum nuchae?
- Superior and posterior extension of the supraspinous ligament (fascial like)
- Covers C1 to C6
What is the most superior spinous process the supraspinous ligament reaches?
C7
What are the 4 compartments of the neck?
- Visceral compartment
- 2x vascular compartments
- Vertebral compartment
What are the fascia which divide the compartments of the neck?
- Superficial facia
- Investing fascia
- Pretracheal fascia
Buccopharyngeal fascia - Prevertebral fascia
- Carotid sheath
What does the investing fascia cover?
- Sternoclydomastoid
- Trapezius
- Supra and infra hyoid muscles
What does the pretracheal fascia cover?
- Oesophagus
- Trachea
- Thyroid and parathyroid gland
What part of the pretracheal fasicia is called buccopharyngeal fascia?
Posterior part
What does the prevertebral fascia surround?
- Vertebral column plus spinal nerves pre and post vertebral muscles
Where does the prevertebral fascia extend from?
Base of the skull to the superior mediastinum (T3)
What is the danger space?
The alar space - within prevertebral layer (alar fascia anf deep prevertebral layer) area extends from base of skull though posterior mediastinum to diaphragm
What is the true retropharyngeal space?
Between bucopharyngeal fascia and superficial prevertebral fascia (alar fascia); area extends between base of skull and superior mediastinum. Pharynx infection can spread through this to post. mediastinum
What is the pretracheal space?
Between investing layer and pretracheal fascia; area extends between neck and superior mediastinum
What 2 spaces are indistinguishible in healthy people?
True retropharyngeal and danger/alar space
What do vertebral vessels travel in up the neck?
Foramen transversarium (found on transverse process)
What cervical vertebra does the vertebral artery not travel through?
C7
What cervical vertebra does the vertebral vein not pass through?
C6
What should you see on an adequate cervical x-ray?
All 7 cervical vertebrae and the occipital bone
What is the curve like on the cervical spine?
Lordotic curve (-43deg arc)
- You should be able to draw a line from:
- Ant + Post vertebral bodies
- Lamina junctional line
- Posterior tip of spinous processes
