Osteology of the Head and Neck Flashcards
Where does movement occur in the skull?
the mandible at the temporomandibular joint (TMJ) & the atlanto-occipital joint
What is the function of the skull?
Protects the brain, brainstem, cranial nerves & associated blood vessels
Provides attachment for muscles Provides a framework for the head Gives us our identity as individuals…
What types of bones are in the skull?
flat and irregular bones
pneumatised bones
What type of osstification are flat smooth bones?
intramembranous
What type of ossification are irregular bones?
endochondral
What are pneumatised bones? What is the purpose of them?
What are examples?
Pneumatised bones: Bones with air spaces (air cells or sinuses) such as the frontal, temporal, sphenoid & ethmoid
Why? Reduce weight & add resonance to our voice
How many bones are in the skull?
total of 22 bones in the adult excluding the ossicles of the ear (28 with ossicles)
What is the neurocranium?
Bony case of the brain including cranial meninges with a dome-like roof (calvaria/skullcap) & a floor (cranial base/basicranium)
What is the viscerocranium?
(facial skeleton):
Anterior part of cranium that consists of bones surrounding the oral cavity, nasal cavity & most of the orbit
What are the bones of the neurocranium?
8 bones
Frontal
Parietal x2
Occipital
Sphenoid
Temporal x2
Ethmoid
What are the bones of the viscerocranium?
15
Ethmoid
Palatine x2
Lacrimal x2
Nasal x2
Zygomatic x2
Vomer
Inferior nasal concha x2
Maxilla x2
Mandible
What are the main features of the viscerocranium?
Zygomatic arch, mandible & infratemporal fossa
What are the main features of the neurocranium?
External acoustic meatus (opening), styloid & mastoid processes & temporal fossa
What is at the borders of the temporal fossa?
*including the floor
Superior & posterior borders: Superior & inferior temporal lines
Anterior border: Frontal process of zygomatic bone & zygomatic process of frontal bone
Inferior border: Infratemporal crest deep to zygomatic arch
Floor: Includes pterion
What is the pterion?
h-shaped junction of sutures
includes the frontal, parietal, temporal, & greater wing of sphenoid bone
thin and vulnerable
What does the pterion overlie?
anterior branch of the middle meningeal artery
trauma can lead to extradural (epidural) haematoma
Where is the surface anatomy of the pterion?
superior to midpoint of zygomatic arch & posterior to frontal process of zygomatic bone
What is the calvaria composed of?
4 bones
4 flat bones (2x parietal, single frontal & occipital) fused by the coronal, sagittal & lambdoid sutures
What is the bregma?
what is it in the neonate
the midline bony landmark where the coronal and sagittal sutures meet, between the frontal and two parietal bones. It is the anterior fontanelle in the neonate and closes in the second year
What are granular foveolae found in the calvaria?
what is their role?
Arachnoid granulations (return CSF to the venous circulation)
What are sutures and what is their movement?
- Structurally, type of fibrous joint
- Functionally, limited or no movement
(synarthrosis)
What are fontanelles?
- Moulding of cranial shape during birth
- Post-natal growth of brain
- Corners of frontal & parietal bones fuse by 18 months (anterior fontanelle not palpable)
What are flat bones seperated by?
by fibrous membranes that fuse in post-natal life (sutures)
What are the accessory/wormian/sutural bones?
which suture are they most commonly found in?
- Small islands of bone may be seen within a cranial suture
- Most commonly observed in the lambdoid suture
What are the exit points of CN V divisions?
supra-orbital notch (foramen)
infra-orbital foramen
mental foramen
What are craniometric points?
Craniometric points (CPs) are landmarks on the skull that are important in radiology and surgery
What are the craniometric points?
8
asterion
inion
lambda
vertex
bregma
pterion
glabella
nasion
What part of the palate is bony?
anterior 2/3
What part of the palate is soft?
posterior 1/3
Why are injections in the hard palate painful?
The hard palate mucosa is tightly bound to the underlying bone & submucous injections here are very painful
Why does an injection into the gingiva of a tooth anesthestises the adjacent mucosa of the palate?
The superior lingual gingiva, the part of the gingiva covering the lingual surface of the teeth & the alveolar process of the maxilla, is continuous with the mucosa of the palate,
What bones does the anterior cranial fossa have?
frontal, ethmoid and sphenoid
Where is the anterior cranial fossa?
shallowest part of cranial base - occupied by frontal lobes
What significance does the foramina of the cribiform plate hold?
Olfactory bulbs (CN I) receive nerve fibres from the nasal cavity via the foramina of the cribriform plate (olfaction)
What can cribriform plate (of ethmoid bone) fractures present with?
CSF rhinorrhoea
What bones does the middle cranial fossa house?
- Sphenoid & temporal bones
- Occupied by temporal lobes
Where is the PG?
the pituitary gland lies in the hypophyseal (pituitary) fossa (deepest part of sella turcica)
What is the PG surrounded by?
pituitary gland is surrounded by 4 clinoid processes & 2 superior projections (dorsum sellae posteriorly & tuberculum sellae anteriorly)
What bones are in the posterior cranial fossa and what is it occupied by?
- Sphenoid, occipital & temporal bones
- Occupied by the cerebellum & medulla, & pons
What does the foramen magnum house?
medulla oblongata (brainstem)
What surrounds the infratemporal fossa?
laterally, medially, anteriorly, posteriorly, superiorly, inferiorly
Laterally: Ramus of the mandible
Medially: Lateral pterygoid plate of sphenoid bone
Anteriorly: Posterior aspect of maxilla
Posteriorly: Tympanic plate, mastoid & styloid processes
Superiorly: Infratemporal crest of sphenoid bone
Inferiorly: Angle of the mandible
What does the infratemporal fossa communicate with?
communicates with the temporal fossa through the interval between (deep to) the zygomatic arch & (superficial to) the cranial bones
Where does the pteryogopalatine fossa lie?
between the pterygoid process of the sphenoid bone and the posterior aspect of the maxilla
Where does the pterygomaxillary fissue lead?
leads to pterygopalatine fossa like a door
What is medial to the pterygopalatine fossa?
what does the pterygopalatine fossa lead to?
sphenopalatine foramen
What are noteable foramina in the anterior cranial fossa?
what do they containn?
cribriform foramina in cribriform plate - axons of olfactory cells in olfactory
What are the noteable foramina in the middle cranial fossa?
optic canals
superior orbital fissure
foramen rotundum
foramen ovale
foramen spinosum
foramen lacerum
6
What are the contents of the optic canals?
optic nerves (CNII) and ophthalmic arteries
What are the contents of the superior orbital fissure?
ophthalmic veins, ophthalmic nerve (CNV1), CNIII, IV and VI and sympathetic fibres
What are the contents of the foramen rotundum?
maxillary nerve (CNV2)
What are the contents of the foramen ovale?
mandibular nerve (CNV3)
accessory meningeal artery
lesser petrosal nerve
What are the contents of the foramen spinosum?
middle meningeal artery and vein and meningeal branch of CNV3
What are the contents of the foramen lacerum?
deep petrosal nerve
greater petrosal nerve
internal carotid passes horizontally to FL
What are the noteable foramina of the posterior cranial fossa?
3
foramen magnum
jugular foramen
hypoglossal canal
What are the contents of the foramen magnum?
medulla and meninges, vertebral arteries, CN XI, dural veins, anterior and posterior spinal arteries
What are the contents of the jugular foramen?
CN IX, X and XI, superior bulb of internal jugular vein, inferior petrosal and sigmoid sinuses and meningeal branches of ascending pharyngeal and occipital arteries
What are the contents of the hypoglossal canal?
hypoglossal nerve (CN XII)
What is the cervical spine made of and what movement does it allow?
- Concave posteriorly
- 7 vertebrae
- Allows lateral flexion
& rotation
What unique features do only cervical vertebrae have?
foramen transversarium
What vertebrae are typical?
c3-c6
What vertebrae are atypical?
c1, c2, c7
What vertebrae have bifd spinous processes?
c2-c6
Why is c1 atypical?
atlas
anterior & posterior arches, no body, no spinous process instead tubercle, facets articulate with occipital condyles of skull or dens)
What are the joints of the cervical vertebrae?
lateral atlanto-axial joint
atlanto-occipital joint
Why is c2 atypical?
axis
dens/odontoid process
What does the lateral atlanto-axial joint and pivot joint of dens allow?
what ligament is it assisted by?
Allows rotation of head (side-to- side movements); assisted by transverse ligament of atlas holding dens in position
What does the atlanto-occiptal joint allow?
Allows flexion & extension (nodding); between the occipital condyles of the skull; condyloid joint
What is the role of alar ligaments?
prevent excessive rotation of head & neck, connect dens to occipital condyles
What is between c1 and c2?
No intervertebral disc between C1 & C2!
What is the highest point of the skull?
vertex
What type of structural joints are sutures?
fibrous
syntharthosis
What forms the pterion and why is it important clinically?
sqamous part of temporal
greater wing of sphenoid
parietal
frontal
Weakest Part of the Skull: It is considered the weakest part of the skull because it is where multiple bones meet and the skull is relatively thin
Middle Meningeal Artery: The anterior division of the middle meningeal artery runs beneath the pterion. A traumatic blow to this area can rupture the artery, leading to an epidural hematoma, a potentially life-threatening condition
Alar ligament vs Transverse ligament
The alar ligament restrains rotation of the upper cervical spine, whereas the transverse ligament restricts flexion as well as anterior displacement of the atlas
