2 - Osteology of the skull, hyoid and cervical spine Flashcards
What is the function of the skull?
- protects brain, brainstem, cranial nerves and vasculature
- attachment for muscles (bony landmarks)
- framework for head and identity
What are the different types of bone in the skull?
- flat bones, formed by intramembranous ossification
- irregular bones, formed by endochondral ossification
- pneumatised bones, bones that have air spaces (ie sinuses), reduce the weight of the skull
What are the divisions of the skull?
- neurocranium, made up of the vault (calvaria) and the cranial base
- viscerocranium (facial), anterior part of the skull surrounding the orbit, nasal and oral cavities
- mandible
What are the 8 bones of the neurocranium?
- occipital
- parietal x2
- frontal
- temporal x2
- sphenoid
- ethmoid
What are the 14 bones of the viscerocranium?
- zygomatic x2
- maxilla x2
- palatine x2
- nasal x2
- vomer
- inferior nasal conchae x2
- lacrimal x2
- mandible
What are the main features of the norma lateralis?
Neurocranium
- external acoustic meatus
- styloid process
- mastoid process
- termporal fossa
Viscerocranium
- zygomatic arch
- mandible
- infratemporal fossa
Describe the borders of the temporal fossa.
Superior = superior temporal line
Inferior = infratemporal crest, deep to zygomatic arch
Anterior = frontal process of zygomatic bone, zygomatic process of frontal bone
Posterior = inferior temporal line
Floor = pterion
What is the correct anatomical plane of the skull?
- orbito-meatal line / Frankfort horizontal plane
- runs from the superior border of external acoustic meatus to the inferior border of the orbit
What is the asterion?
Star shaped junction of the occipital, parietal and temporal bones
What is the inion?
Most prominent protuberance of the back of the skull
What is the lambda?
- junction of the lambdoid and sagittal suture
- located at the rear of the skull
What is the vertex?
Superior and middle point of the vault of the skull
What is the bregma?
Junction of the sagittal and coronal sutures
What is the glabella?
- smooth part of bone at the most anterior protuberance of the forehead
- “hairless” in greek
What is the naison?
- junction of the nasal sutures
What is the pterion?
- H-shaped junction of sutures
- junction between the frontal, temporal (squamous), parietal and the greater wing of the sphenoid bones
- structurally thin, and overlies the anterior branch of the middle meningeal artery
- “wing” in greek
What is a sutural bone?
- small island of bone found in the suture between two bones
- commonly observed in the lambdoid suture
What are sutures?
- structurally a fibrous joint
- limited to no movement = synarthrosis
What is a fontanelle?
- soft spots in the skull that fuse after birth
- allow for delivery by the birth canal and post natal growth of the brain
When does the anterior fontanelle close?
18 months
When does the posterior fontanelle close?
Not palpable by 1 year
When does mandibular symphasis finish?
2 years
What are the paranasal sinuses?
- frontal sinuses
- ethmoidal cells
- maxillary sinuses
What passes through the carotid canal?
Internal carotid artery
What passes through the jugular foramen?
- internal jugular vein
- CN IX
- CN X
- CN XI
What passes through the foramen magnum?
- spinal cord
- meninges
- spinal arteries
- CN XI
What passes through the foramen ovale?
- CN V3
- accessory meningeal artery
What passes through the foramen spinosum?
- middle meningeal artery
- CN V3
What passes through the hypoglossal canal?
CN XII
What comprises the cervical spine?
- 7 vertebrae
- concave posteriorly, which allows lateral flexion and rotation
What is the ligamentum nuchae?
- supports the head and resists flexion
- attaches to external occipital protuberance (most posterior part of skull) and the foramen magnum to the spinous processes of the vertebrae
- continuous with supraspinous ligament (which connects the apices of the spine)
What are the typical cervical vertebrae?
C3-C6
Describe a typical cervical vertebrae.
- body
- bifid spinous process, which connects to the body via the lamina and the superior articular facet
- anterior and posterior tubercles, which are connected by the transverse process which is lateral to the foramen transversarium
- vertebral foramen for the spinal cord
Describe C7.
- body
- non-bifid elongated spinous process, which connects to the body via the lamina and the superior articular facet
- anterior and posterior tubercles, which are connected by the transverse process which is lateral to the foramen transversarium
- vertebral foramen for the spinal cord
Describe C1.
- known as the atlas
- posterior and anterior arches connected by the lateral mass and the superior articular facet for the occipital condyle
- articular facet for the dens
Describe C2.
- known as the axis
- body with a dens (pivot for the atlas)
- bifid spinous process, which connects to the. body via the lamina and the superior articular facet for the atlas
What is the lateral Atlanto-axial joint?
- pivot joint of the dens
- allows rotation of the head (side-side)
- assisted by transverse ligament
What is the atlanto-occipital joint?
- allows flexion
- allows extension (nodding)
What are the alar ligaments?
- prevent excessive rotation
- connects dens to occipital condyles
What is the hyoid bone?
- u shaped bone at C3 level in the anterior neck
- doesn’t articulate with any bones
- suspended by muscles and ligaments
Describe the hyoid.
- u shaped
- body of the hyoid bone has 2 lesser horns
- 2 greater horns extend posteriorly
