Osteology of skull, hyoid & cervical spine Flashcards
what is the most complex bony structure in the body?
The skull
- made up of 23 separate bones
what are the functions of the skull?
- houses & protects the brain, brain stem, cranial nerves & vasculature
- protects the 5 organs of special sense
- provides attatchment for muscles
- provides framework for the head
what are the 5 special senses?
- olfaction (smell)
- vision
- taste
- vestibular function
- auditory function
what is the atlanto-occipital joint?
joint at base of skull & cervical spine
what type of bones is the skull composed of?
- flat bones
- irregular bones
- pneumatised bones
what is the difference between flat and irregular bones?
FLAT BONES
- formed by intramembranous ossification
IRREGULAR BONES
- formed by endochondral ossification
what are pneumatised bones?
bones with air spaces (air cells or sinuses)
what are examples of pneumatised bones?
- frontal bone
- temporal bone
- sphenoid bone
- ethmoid bone
what are the functions of pneumatised bones in the skull?
- reduce weight of skull
- add resonance to our voice
what are the developmental divisions of the skull?
Neurocranium
- portion of skull that protects the brain & organs of special sense
Viscerocranium
- facial skeleton (relating to the digestive & respiratory systems)
what is the Norma Frontalis?
the anterior view of the skull
what is the Norma Lateralis?
the lateral (side) view of the skull
what is the Norma Occipitalis?
the posterior view of the skull
what is the Norma Basalis?
the inferior view of the skull
what is the Norma Verticalis?
the superior view of the skull
What bones make up the Neurocranium?
- Frontal
- Parietal x2
- Occipital
- Sphenoid
- Temporal x2
- Ethmoid
what bones make up the Viscerocranium?
- Ethmoid
- Palatine x2
- Lacrimal x2
- Nasal x2
- Zygomatic x2
- Vomer
- Inferior Nasal Concha x2
- Maxilla x2
- Mandible
what is the zygomatic arch?
arch formed between the temporal process of the zygomatic bone and the zygomatic process of the temporal bone
what is the external acoustic meatus?
the ear canal!
What is the temporal fossa?
an area on the side of the cranium from which the temporal muscle arises
What are the anterior borders of the temporal fossa?
- frontal process of zygomatic bone
- zygomatic process of frontal bone
what is the inferior border of the temporal fossa?
- infratemporal crest deep to zygomatic arch
What is the Vertex?
superior point of the neurocranium and is centred in the middle
junction of the sagittal & coronal suture (where they meet)
what is the Lambda?
junction of the lambdoid and sagittal sutures
what is the Inion?
most prominent point of the external occipital protuberance
what is the Asterion?
star shaped junction between the occipital, parietal and temporal bones
What is the nasion?
where the frontonasal and internasal sutures meet
what is the Glabella?
- a smooth part of frontal bone superior to the root of the nose
- the most anterior projecting part of the forehead
What is the Pterion?
- H-shaped junction of sutures (where the frontal, parietal, temporal & greater wing of sphenoid meet)
What is interesting about the Pterion?
structurally weak point of the skull
Why is an injury to the pterion clinically relevant?
- vulnerable to injury as structurally weak
- overlies the anterior branch of middle meningeal artery
- if pterion fractures this artery may rupture
what can trauma to the pterion lead to?
rupture of the anterior branch of middle meningeal artery which can cause an extramural haematoma (bleed between skull & dura)
How can the surface anatomy of the Pterion be described?
- 4cm superior to midpoint of zygomatic arch
- 3cm posterior to frontal process of zygomatic bone
what are Wormian bones?
irregularly shaped small bones found along sutures that occur naturally
- most commonly seen on lambdoid sutures
What are sutures?
a type of fibrous joint (bound together by Sharpey’s fibres)
What are fontanelles?
fibrous membranes that fuse in post-natal life
- allow for moulding of cranial shape during birth
what is the Vomer bone?
forms the posterior inferior part of nasal septum
what passes through the carotid canal?
Interior carotid artery
what passes through the Jugular foramen?
- inferior petrosal sinus
- sigmoid sinus
- posterior meningeal artery
- cranial nerves IX, X and XI (glossopharyngeal, vagus and accessory)
what passes through the foramen magnum?
- medulla oblongata
- venous plexus
What passes through the Foramen Spinosum?
- middle meningeal artery
- middle meningeal vein
- meningeal branch of the mandibular division of trigeminal nerve CNV3
how many cervical vertebrae are there?
7 cervical vertebrae
- C1 to C7
What vertebrae are considered atypical?
C1, C2 and C7
What vertebrae are considered typical?
C3 to C6
what is vertebrae C1 also known as?
Atlas
What are the characteristics of vertebrae C1?
- no body
- no spinous process
- has an anterior arch and a posterior arch
- facets articulate with occipital condyle of skull or dens
what is vertebrae C2 also known as?
Axis
what are the characteristics of vertebrae C2?
- dens (odontoid process) located on bodies superior surface
- spinous process is large and bifid
what is characteristic of vertebrae C7?
long spinous process that is NOT bifid
what is the function of Alar ligaments?
prevent excessive rotation of head & neck, also connect dens to occipital condyles
what is the Hyoid bone?
U-shaped bone found at C3 level in anterior neck
- does NOT articulate with any other skeletal elements
- suspended by muscles & ligaments
How many vertebrae are in the cervical spine?
7
What structures does the ligamentum nuchae attach to?
attaches external occipital protuberance & foramen magnum to the spinous processes of clinical vertebrae (to C7)
what is the function of the ligamentum nuchae?
supports head & resists flexion, attachment point for muscles
