cranial fossa Flashcards
what does the anterior cranial fossa form?
the roof of the orbit, contributes to the nasal cavities and has foramina related to the special senses of vision and smell
what lobes of the brain are found in the anterior cranial fossa?
the frontal lobes
what is the attachment site for the dura mater?
the crest Galli - a bony ridge formed by the frontal bone
the cribriform plate is part of which bone?
the ethmoid bone
in life what lies on the superior surface of the cribiform plate?
the olfactory bulbs
what bone that contributes to the anterior cranial fossa contains the optic canals?
the sphenoid bone
what is the function of the optic canals?
allow optic nerves (Cn2) and ophthalmic arteries to pass between the orbit and inside the skull
explain the contribution of the sphenoid bone to the middle cranial fossa
the sphenoid bone contributes to the floor of hte middle cranial fossa and forms the floor of the orbital fissures, foramen rotundum, foramen ovale and foramen spinosum
where does the trigeminal nerve divide into its 3 divisions?
it forms a large ganglion that sits on the floor of the middle cranial fossa and here it divides into its three divisions
explain the course of the ophthalmic division of the trigeminal nerve (V1)
it is a sensory nerve that passes through the superior orbital fissure to reach the orbit
what nerves accompany the ophthalmic division of the trigemianl nerve as it passes through the superior orbital tissue to reach the orbit?
oculomotor (CN3), trochlear (CN4) and abducens (CN6)
explain the course of the maxillary division of the trigeminal nerve (V2)
it carries sensory nerves which pass through the foramen rotundum to pass towards the maxilla
explain the course of the mandibular division of the trigeminal nerve (V3)
it carries motor and sensory fibres through the foramen ovale to the infratemporal fossa
apart from the mandibular division of the trigeminal nerve what else passes through the foramen ovale?
the otic ganglion, the accessory meningeal artery, the lesser petrosal nerve and emissary veins
what does the foramen spinosum carry?
the middle meningeal artery
where does the middle meningeal artery arise from and what does it supply?
is a branch of the maxillary artery
supplies blood to the dura
what foramen allows the internal carotid artery to enter the middle cranial fossa?
the foramen lacerum
what lobes of the brain lie in the middle cranial fossa?
the temporal lobes
how does the internal carotid artery enter the skull?
via the carotid canal
explain the course of the internal carotid artery
it enters the skull via the carotid canal then turns away from the canal and enters the top of the foramen lacerum it does not pass all the way through the foramen lacterum and small blood vessels transverse the length of the foramen lacterum
the artery then lies either side of the body of the sphenoid bone where it will enter the cavernous venous sinus before contributing to the circle of willis
which bones make up the posterior cranial fossae?
the temporal bone (contributes to the floors of both the middle and posterior cranial fossae)
the occipital bone (forms most of the floor of the posterior fossa)
which structures pass through the jugular foramen?
the internal jugular vein
the glossopharyngeal nerve
the vagus nerve
the accessory nerve
which structures pass though the foramen magnum?
the spinal cord and its meninges (leaving the skull)
the vertebral arteries and part of the accessory nerve (entering the skull)
what structure passes through the hypoglossal canal?
the hypoglossal nerve (exiting the skull)
what structure passes through the hypoglossal canal?
the hypoglossal nerve (exiting the skull)
what part of the brain lies in the posterior cranial fossa?
the cerebellum
what sits in the petrous bit of the temporal bone?
the internal acoustic meatus
what passes through the internal acoustic meatus?
the facial nerve and vestibular cochlear nerve (exiting the cranial cavity and entering the temporal bone)
explain the course of the trigeminal nerve
it forms a ganglion before dividing into its 3 divisions
what is the first cranial nerve?
the olfactory nerve
what is the function of the olfactory nerve?
provides special sense of taste
explain the course of the olfactory nerve
it passes from the mucosa in the nose through the cribiform plate to synapse on the olfactory bulb
what is the second cranial nerve?
the optic nerve
what is the function of the optic nerve?
provides special sense of vision
explain the course of the optic nerve
the optic nerves form a chiasm where some fibres from each eye cross over to the other side of the chasm. the optic tracts pass info from the chiasm to other areas of the brain such as the thalamus and then fibres pass to the occipital lobe to be processed by the visual cortex
what is the third cranial nerve?
the oculomotor nerve
where does the oculomotor nerve arise from?
the midbrain (it is one of two nerves to arise from the midbrain)
what is the function of the occulomotor nerve?
it innervates the extraoccular muscles and changes the shape of the lens and the pupil
what is the fourth cranial nerve?
the trochlear nerve
what is the function of the trochlear nerve?
motor fibres to one extra ocular muscle - superior oblique
what is the fifth cranial nerve?
the trigeminal nerve
what is the function of the trigeminal nerve?
supplies muscles of mastication and sensory innervation to the face
where does the trigeminal nerve originate?
from the pons
what is tensor tympani?
a small muscle in the middle ear that attaches to the malleus and dampens vibrations from the tympanic membrane to prevent damage to the inner ear structures
what is the function of tensor veli palatini?
helps to tense the soft palate
describe the trigeminal innervation of the tongue
the trigeminal nerve supplies general sensation to the anterior two thirds of the tongue
what is the sixth cranial nerve?
abducens
what is the function of abducens?
carries motor fibres to one extraoccular muscle - lateral rectus
where does abducens originate from?
the pons
what passes through the cavernous venous sinus?
the cavernous venous sinus has cranial nerves 3, 4, 5 and 6 and the internal carotid artery passing through it
explain the passage of CN3, 4, 5 and 6 through the cavernous venous sinus?
CN3, 4 and 5 pass in the lateral wall of the cavernous venous sinus but CN6 runs through the middle w/ the internal carotid artery
what is the seventh cranial nerve?
the facial nerve
what is the main function of the facial nerve?
supply motor innervation to the muscles of facial expression and suprahyoid muscle
what is the sensory function of the facial nerve?
general sensation to part of the auricle
special sense of taste from the anterior two thirds of the tongue
what is the eighth cranial nerve?
vestibulocochlear
what is the function of the vestibulocochlear nerve?
vestibular parts - balance
cochlear parts - hearing
what is the ninth cranial nerve?
glossopharyngeal
what are the modalities of the glossopharyngeal nerve?
motor, sensory, special sense and parasympathetic
where does the glossopharyngeal nerve supply w/ general sensation?
the soft palate (gag reflex)
the pharynx
many parts of the ear
how doe the glossopharyngeal nerve carry parasympathetic fibres to the parotid gland?
it communicates via the lesser petrosal nerve w/ the auriculotemporal branch of the trigeminal nerve to carry parasympathetic fibres to the parotid gland
what is the tenth cranial nerve?
the vagus nerve
what are the modalities of the vagus nerve?
sensory
motor
parasympathetic
explain the course of the vagus nerve
it sends a recurrent laryngeal branch that wraps around the aortic arch on the left and the subclavian artery on the right
the nerves then ascend the neck between the oesophagus and trachea to supply the intrinsic muscles of the neck
what is the eleventh cranial nerve?
the accessory nerve
what is the function of the accessory nerve?
carries motor fires to supply SCM and trapezius
explain the innervation of the soft palate
the innervation of the soft palate is either the cranial part of the accessory nerve or the vagus nerve
what its the olive?
cranial nerves 9, 10 and 11 originate posterior from a lump on the medulla called the olive
what is the twelfth cranial nerve?
the hypoglossal nerve
where does the hypoglossal nerve originate from?
it is the only cranial nerve to originate from the medulla, anterior to the olives
what is the function of the hypoglossal nerve?
it supplies most of the musculature of the tongue
it is only motor - it does not provide any sensory innervation to the tongue or oral cavity
