Theme 8 part 2 Flashcards
what is intramembrous ossification
mesoderm to bone
what is endochondral ossification
cartilage to bone
how does the cranial vault form
intramembranous ossification
how does the cranial base form
endochondral ossification
how does the facial skeleton form
intramembranous ossifcation (neural crest)
what are the unpaired bones of the skull in the interior cranium
frontal
ethmoidal
occipital
sphenoid
what are the paired bones of the skull in the interior cranium
parietal
temporal
what is the boundary between the middle and anterior cranial fossa
lesser wings of sphenoid
anterior clinoid process and jugum sphenoidale
what is the boundary between the middle and posterior cranial fossa
superior borders of the petrous temporal bones, posterior clinoid processes and dorsum sellae
what are the features of the anterior cranial fossa
crista galli
cribriform plate
orbital plate of frontal bone
What are the features of the middle cranial fossa ?
Jugum sphenoidale sella turcica pituitary fossa optic canal Fo. Lacerum Superior orbital fissure Fo.Rotundum Fo. Ovale Fo.Spinosum Hiatus for the greater and lesser petrosal nerves
What are the features of the posterior clinoid fossa ?
Clivus Fo. Magnum Hypoglossal canal jugular Fo Internal auditory meatus Internal occipital protuberance
Which cranial nerves emerge in the anterior cranial fossa ?
I
olfactory
Which cranial nerves emerge in the middle cranial fossa ?
II, III, IV, V, VI optic oculomotor trochlear trigeminal abducens
Which cranial nerves emerge from the posterior cranial fossa ?
VII, VIII, IX, X, XI, XII Facial vestibulocochlear glossopharyngeal vagus spinal accessory hypoglossal
What are the 3 layers of the meninges (part of protective tissue)?
dura matter
arachnoid matter
pia matter
what are the four parts of dura matter
falx cerebri
falx cerebelli
diaphragma sella
tentorium cerebelli
What does the falx cerebri do ?
hangs down into the cranial cavity and separates the 2 cerebral hemispheres
What does the falx cerebelli do ?
separates the right and left cerebellar hemispheres
What is the diaphragma sellae do ?
a small fold between the anterior and posterior clinoid processes
What are the 2 spaces between the meningeal layers ?
extradural space
subarachnoid space
What is the extradural space ?
space between the dura and the bone
What is the subarachnoid space ?
below the arachnoid mater and is filled with CSF
where do the frontal lobes of the cerebral hemisphere normally rest
the orbital plate of the frontal bone
where do the temporal lobes of the cerebral hemisphere normally rest
greater wing of sphenoid
what would damage to the middle meningeal artery cause
extradural haemorrhage
where is the petrous sinus located
on the superior border of the petrous temporal bone
what bone is the dorsum sellae apart of
sphenoid
which bone is the cerebellar fossa located in
squamous part in temporal bone
where does the cerebellum rest
cerebellar fossa
where is the transverse sinus located
groove on the occipital bone
where is tentorum cerebelli usually attached
to the margins of the grooves on the occipital bone
where is the superior sagittal sinus located
Groove on the inferior surface of the calvarium in the midline on the frontal bone and extending onto the parietal bones on either side of the sagittal suture
where does the superior sagittal sinus drain
transverse sinus at confluence of sinuses
which groove does the internal carotid artery pass medial to
groove in the body of the sphenoid bone where the carvenous sinus is located
which nerves enter at the internal auditory meatus
facial and vestiboluocochlear
what would happen if there was damage to the facial nerve at the internal auditory meatus
ipsilateral facial paralysis combined with a loss of taste to the anterior ⅔of the tongue, loss of the stapedial reflex and loss of lacrimal gland secretion
what would happen if there was damage to the vestibulocochlear nerve
hearing loss and balance affected
where does the trigeminal ganglion lodge
trigeminal impression
what would happen if there was damage to the spinal accessory
nerve (XI)paralysis of the sternocleidomastoid and trapezius muscles
what would happen if there was damage to the vagus nerve
loss of sensation from the larynx and the thoracic and abdominal viscera and paralysis of the muscles of the larynx, pharynx and soft palate and muscles lining the thoracic and abdominal viscera
what would happen if there was damage to the glossopharyngeal nerve
loss of touch and taste sensation from the posterior ⅓ of the tongue, loss of sensation from the oropharynx and from the carotid chemo- and baroreceptors, paralysis of stylopharyngeus and loss of parotid salivary secretion.
how does the cerebrospinal fluid (CSF) protect the brain
Lies between the meningeal layers: arachnoid and the pia mater
It acts as a shock absorber
how do the Meningeal reflections (CSF) protect the brain
Helps protect the brain from mechanical damage
shock absorbers
how do the Venous sinuses protect the brain
Help in cooling the brain and protect if against transient fluctuations in venous pressure
how do the bones of the skull help protect the brain
through their thickness and immobility of their joints (sutures)
Do venous sinuses contain valves?
no
What do the dural venous sinuses do ?
drain blood from the brain into the internal jugular vein and the jugualr foramen
What does the superior sagittal sinus drain into ?
the confluence
What does the inferior sagittal sinus do ?
turns into the straight sinus as it approaches the tentorium cerebelli
What is the transverse sinus ?
passes laterally from the confluence and becomes the sigmoid sinus as it passes to the petrous temporal bone
What is the sigmoid sinus ?
continues medially from the petrous ridge to the jugular fo. All blood drains into the sigmoid sinus
What are the cavernous sinuses ?
lie in the body of the sphenoid on either side of the sella tursica - draineed by the superior and inferior petrosal sinuses
What does the superior petrosal sinus do ?
drains into the cavernous sinus
What does the inferior petrosal sinus do ?
drains directly into the internal jugular vein
What is the arterial supply of the brain ?
vertebral and the internal carotid arteries
How does the internal carotid artery enter the posterior cranial fossa ?
through the carotid canal
How does the vertebral artery enter the posterior cranial fossa ?
foramen magnum
what are the foramina in the anterior cranial fossa
cribriform plate- olfactory nerves
what are the foramina in the middle cranial fossa
superior orbital fissure optic canal rotundum ovale spinosum lacerum hiatus for greater petrosal hiater for lesser petrosal
what are the foramina in the posterior cranial fossa
internal auditory meatus
jugular
hypoglossal canal
magnum
what are the structural buttresses of the skull
areas of bone that are the most structurally stable and are the least likely to break
what does the buttress system do
absorbs and transmits forces applied to the facial skeleton to protect fragile bony areas
what is an extradural haemorrhage and what structure does it affect
bleeding between dura and skull- middle meningeal
what is a sub haemorrhage and what structure does it affect
bleeding in subdural space- superior cerebral veins
what is a subarachnoid haemorrhage
bleeding into the subarachnoid- aneurysms, angiomas
what is a intracerebral haemorrhage and what structure does it affect
bleeding into brains itself- middle cerebral artery
what are the typical routes for infection
tissue planes
venous
lymphatic
direct erosion
what are the severe untreated consequences of orofacial infections
airway obstruction
intracranial spread
septicaemia
what will happen if a periapical abscess is left untreated
passes into soft tissues through thin cortical bone before thick bone
where can infection spread in tissue spaces in the jaw and neck
- can spread backwards till it reaches the posterior border of mylohyoid. can spread into submandibular and submental space with infection on either side of mylohyoid pushing tongue up and covering airway- ludwigs angina
- between 2 heads of anterior digastric, left and right
what is ludwigs angina
where airways are obstructed due to the tongue being pushed up and back. this is bc infection has spread to both sides of the mylohyoid
what are the tissue spaces in the lower jaw
sublingual space submental space submandibular space pterygomandibular space peritonsillar space parotid space
Describe the route of infection spread from a 3rd mandibular molar ?
periapical abcess - in the roots of molar
breaks through on the lingual side
enters the sublingual space
spread backward - ludwigs angina
what is quinsy
medical condition caused by pressure on CNIX
where are the tissue spaces in the upper jaw
canine
palatal
infratemporal
where can infection from a lower 3rd molar spread
intraorally- sublingual space
extraorally- submandibular
neck-para- or retropharyngeal spaces
what are the 3 routes of entry for intracranial spread of infection
tissue spaces
paranasal sinuses
venous commincation
what can infections erode
basiocciput
enter the mediastinum
What is the second route of infection spread ?
from submandibular space
into lateral pharyngeal space
retropharyngeal space
Describe a route of infection spread from the cavernous sinus ?
from the cavernous sinus into the emissary veins and the into the infraorbital vein into the facial vein
Describe a second route of infection from the cavernous sinus ?
from the cavernous sinus into the pterygoid plexus of veins and into the RM vein
what is carvenous sinus thrombosis
deep seated infection which will erode the wall of the carvenous sinus which is close to the carotid artery.
what are the types of facial fractures
mandibular fractures
middle third fractures
zygomatic fractures
what are the signs of a fractured zygoma
pain
swelling
problems opening mouth
numbness over the lip, side of nose and teeth in that area
what are the common places for a mandibular fracture
condyle (neck) -thin
angle- grain crosses over so weak spot
mental fo- weak spot
where in an unusual place for a mandibular fracture
coronoid process
what is an indirect fracture
where injury on one side leads to injury on the other side
what is an unfavourbale fracture
where muscle distracts the fracture
what is a favourbale fracture
muscle aligns the fracture
what are the functional problems with mandibular fractures
disturbance in occlusion
nerve damage
AIRWAY PROBLEMS!!!
where would the fracture in the mandible occur for there to be nerve damage
between mandibular and mental fo- numb lower lip on one side
what occurs in bilateral parasymphseal mandibular fractures
the infra glossal muscles pull that segment backwards which also pulls the tongue occluding airways
what is the safest way to open the airway
jaw thrust not head tilt chin lift
what are the growth disturbances in children if the condyle of mandible fractures
mandible grows from the condyle so can be disproportion in the mandible, occlusal facial disturbances
what occurs in bony ankylosis
top condyle fuses with bone to the fossa it sits in leading to limited mouth opening
bone forms between the condyle and fossa
how can mandibular fractures be treated
- Reduction- get bone ends together
- Fixation- keep them together
Re-establish occlusion
what is a middle third fracture
from occlusal surface of upper teeth to the ridge of the nose
where is the anterior facial buttress
frontal bone
where is the middle facial buttress
frontal bone and base of skull
where is the posterior facial buttress
base of skull
how can middle third fractres block airways
middle third of the face is attached to the base of the skull and the force can go down a 45 degree angle and back dwon
if it goes down too much can block airway
how can middle third fractures be treated
ORIF- open reduction and internal fixation
what are the symptoms of zygomatic (malar) fractures- cheek bone (zygomatic arch damage)
pain
limited mouth opening
orbital deformity
redness in the eye- subconjuctiva haemorrhage
what are the fucntional prbelms with a fractures
eyes- one further down, double image, blow out fractures, diplopia due to muscle trapping
nerves
mandibular movement
how can zygomatic fractures be treated
ORIF- incison in buccal sulcus of the mouth or in the lateral eyebrow and insert a plate to fix
