skull anatomy Flashcards
how many bones does the skull have?
22
how are the skulls of the bone divided?
neurocranium
viscerocranium
how many bones of the skull are linked by fibrous joints?
21
what is the only non-fibrous joint of the skull?
synovial temporomandibular joint
what is the function of the neurocranium?
housing the brain
attachment site for the head and neck muscles
what is the function of the viscerocranium?
- Form framework of the face – makes up orbit, nasal cavity and oral cavity
- Contain cavities for special sense organs (sight, taste and smell)
- Opening for air and food passage
- Secure teeth
- Anchor facial muscles of expression
how many cranial bones are there?
8
name all the cranial bones
o 2x parietal, 2x temporal, sphenoid, frontal, ethmoid, occipital
how does the frontal bone change throughout development?
starts as 2 in development and then they fuse
what does a fracture of the ethmoid bone lead to?
CSF leaking into the nose
what is the function of sutures
limit movement of the bones
what bone predominantly makes up the zygomatic arch?
temporal bone
where is the external acoustic meatus found?
outside the temporal bone
what does the temporal bone house?
the middle and internal ear
what houses the internal ear?
petrous part of the temporal bone
what does the sphenoid bone link?
facial skeleton to cranial skeleton
how many pterygoid plates does the sphenoid bone have and what do they do?
4
attachment point for pterygoid muscles (muscles of mastication)
what is the sella turcica?
bony cradle which protects the pituitary gland
what is the function of the clinoid processes?
attachment points for the dura mater in the skull
what are the 3 layers of the meninges?
dura mater
arachnoid mater
pia mater
what are the two layers of dura mater in the skull?
meningeal
periosteal
where is the periosteal layer found?
sticks to the inner layer of the skull
how are inward folds of the dura mater made?
when the meningeal layer of the dura mater pulls away from the periosteal layer
name the inward folds of the meningeal layer of dura mater
falx cerebri
tentorium cerebelli
what does the falx cerebri do?
separates the left and right hemisphere
what does the tentorium cerebelli do?
separates the cerebellum from the cerebrum
what is the function of the inward folds of the meningeal layer?
help compartmentalise the inside of the skull and gives support to the brain
what is the tentorial notch?
hole in the tentorium cerebelli to allow brainstem to pass up to the cerebrum
what are the dural venous sinuses?
a network of endothelial lines spaces which are filled with venous blood in the space between dura mater layers
where is the superior saggital sinus?
at the top of the falx cerebri
where is the inferior saggital sinus?
bottom of the falx cerebri
what does the straight sinus do?
joins the supeiror and inferior saggital sinus
what leads into the transverse sinus?
the straight sinus
where does the sigmoid sinus leave the skull?
through the jugular foramen into the jugular vein
where are the cavernous sinuses found?
either side of the pituitary gland
what runs through the cavernous sinus?
internal carotid artery and some cranial nerves
what do the petrosal sinuses do?
link cavernous sinus to sigmoid and transverse sinuses
what part of the skull do the facial bones form?
anterior skull – make up orbit, oral and nasal cavity
what are the orbits?
Bilateral pyramidal shaped cavity on the anterior aspect of the skull
what is the function of the orbit?
the eyeball, extra-ocular muscles and associated neurovasculature
what bones make up the orbit and what aspect of the orbit do they make up?
frontal (superior), maxilla (inferior), lacrimal, ethmoid (medial), sphenoid, zygomatic (lateral)
which walls of the orbit are thin?
medial and inferior walls
what part of the orbit is most likely to fracture?
medial and inferior walls
what makes up the hard palate?
maxilla anteriorly and palatine bone posteriorly
what makes up the nasal septum?
bony and cartilaginous contributions
what is either side of the crista galli?
cribiform plate
which of the conchae are from the ethmoid bone?
superior and middle
which of the conchae are their own bone?
inferior conchae
what are the paranasal sinuses?
Hollow spaces within the frontal, sphenoid, ethmoid and maxillary bones
what lines the paranasal sinuses?
mucous membrane
where do all the paranasal sinuses drain?
the nose
where is the frontal sinus?
in the frontal bone
which is the largest sinus?
maxillary sinus
explain the drainage in the maxillary sinus
Drains into the middle meatus so it has to be full of mucus before it drains
where is the sphenoid sinus?
behind the nasal cavity
what makes up the ethmoid sinus?
many small sinuses
which bones are most and least developed in the foetal skull?
cranial bones are most developed
facial skeleton is underdeveloped and small - jaw is small and no teeth
do newborns have sinuses?
no
what are fontanelle?
large spaces between bones where sutures havent formed yet in newborns
what is the largest fontanelle?
anterior
how do dehydrated babies present?
depressed anterior fontanelle
how does a raised intercranial pressure in a baby present?
fontanelle bulges
when does the anterior fontanelle close?
18 months
when does the posterior fontanelle close?
12 months
what is the function of the fontanelles?
allows brain to grow; allows baby to be born without skull fracture
what separates the anterior and middle cranial fossa?
the lesser wing of the sphenoid
what separates the middle and posterior cranial fossa?
petrous part of the temporal bone
what does the anterior cranial fossa protect?
the frontal lobes of the brain
what does the middle cranial fossa protect?
temporal lobes
what sits in the posterior cranial fossa?
cerebellum
what passes through the foramen spinosum?
middle meningeal artery
runs into the skull then underneath the pterion
what artery runs under the pterion?
middle meningeal artery
what passes through the jugular foramen?
internal jugular vein
describe the passage of the internal carotid artery
travels through the carotid canal
through temporal bone
to the foramen lacerum then travels superiorly
what is the foramen lacerum?
covered over in cartilage, so nothing passes through this
what is the weakest point in the skull?
pterion
what complication arises if the pterion is fractured?
laceration to middle meningeal artery leading to an extradural haematoma
what bones make up the pterion?
parietal bone, squamous part of the temporal bone, the greater wing of sphenoid and the frontal bone
how many cranial nerves are there?
12
where does the olfactory nerve run?
inferiorly from the olfactory bulb, through perforated cribiform plate of the ethmoid bone to enter the nasal cavity
where does the optic nerve run?
Optic nerve transverses the optic canal to enter the orbit
where does the occulomotor nerve come from?
the midbrain
where does the trochlear nerve come from?
posterior surface of the midbrain
where does the abducens nerve come from?
pons
where do the occulomotor, trochlear and abducens transverse?
the superior orbital fissure to enter the orbit
where does the trigeminal nerve emerge from?
lateral surface of the pons
what are the branches of the trigeminal nerve?
ophthalmic, maxillary and mandibular
where does the opthalmic branch transverse?
superior orbital fissure to enter the orbit
how does the maxillary branch of the trigeminal nerve leave the cranium?
through the foramen rotundum
how does the mandibular branch leave the cranium?
through foramen ovale
where does the facial nerve emerge from?
the pons
where does the facial nerve travel?
into internal acoustic meatus – inside temporal bone
Leaves temporal bone through stylomastoid foramen (on the base of the skull)
Emerges from the pons
where does the vestibulocochlear nerve travel?
emerges from the pons and enters the internal acoustic meatus
where do the glossopharyngeal and vagus travel?
- Glossopharyngeal nerve emerges from lateral surface of medulla oblongata w vagus
- Both exit skull via jugular foramen
where does the spinal accessory nerve travel from?
first 5-6 cervical spinal nerves
describe the passage of the spinal accessory nerve?
- Emerges from the first 5-6 cervical spinal nerves
- Then runs superiorly through foramen magnum alongside the brainstem
- Leaves skull via jugular foramen
what does the spinal accessory nerve innervate?
sternocleidomastoid
trapezius
where does the hypoglossal nerve emerge from?
anterior aspect of the medulla oblongata
where does the hypoglossal nerve run?
through the hypoglossal canal
