Neuroanatomy Flashcards
Which bones make up the anterior cranial fossa?
frontal bone
ethmoid bone
lesser wing of sphenoid bone
Where does the ACF lie over?
superiorly over the nasal and orbital cavities
What does the ACF accommodate?
anteroinferior portions of the frontal lobes of the brain
Where is the crista galli (latin for cock’s comb)?
Midline of the ethmoid bone
Where is the cribriform plate?
Either side of the crista galli
What is the cribriform plate and what does it contain?
a sheet of bone seen either side of the crista galli which contains numerous small foramina
these transmit olfactory nerve fibres (CN I) into the nasal cavity
Also contains anterior and posterior ethmoidal foramen
What does the anterior ethmoidal foramen transmit?
transmits the anterior ethmoidal artery, nerve and vein
What does the posterior ethmoidal foramen do?
transmits the posterior ethmoidal artery, nerve and vein
The cribriform is the thinnest part of the ACF and is most likely to fracture. What are the 2 clinical consequences of this?
Anosmia
CSF rhinorrhoea
What forms the body of the middle cranial fossa?
the body and greater wing of the sphenoid
squamous and petrous parts of the temporal bone
What forms the central part of the middle cranial fossa?
the body of the sphenoid bone
What does the central part of the MCF contain and what is its role?
sella turcica
holds the pituitary gland
What are the 3 parts of the sella turcica?
- tuberculum sellae
- pituitary fossa
- dorsum sellae
What is the sella turcica surrounded by?
the anterior and posterior clinoid processes
What is the tentorium cerebelli and what is attached to?
a membranous sheet that divides the brain.
attached at clinoid processes
separates occipital and temporal cerebral hemisphere from the cerebellum and infratentorial brainstem
Where are optic canals (foramina) and what do they transmit?
situated anteriorly in the middle cranial fossa
transmit the optic nerves (CN II) and ophthalmic arteries into the orbital cavities
What 4 foramina are lateral to the central part of the middle cranial fossa?
superior orbital fissure
foramen rotundum
foramen ovale
foramen spinosum
Where does the superior orbital fissure open and what does it transmit?
opens anteriorly into the orbit
transmits the oculomotor nerve (CN III), trochlear nerve (CN IV), ophthalmic branch of the trigeminal nerve (CN V1), abducens nerve (CN VI), opthalmic veins and sympathetic fibres
Where does the foramen rotundum open and what does it transmit?
opens into the pterygopalatine fossa
transmits the maxillary branch of the trigeminal nerve (CN V2)
Where does the foramen ovale open and what does it transmit?
opens into the infratemporal fossa
transmits the mandibular branch of the trigeminal nerve (CN V3) and accessory meningeal artery
Where does the foramen spinosum open into and what does it transmit?
opens into the infratemporal fossa
transmits the middle meningeal artery, middle meningeal vein and a meningeal branch of CN V3
What does the carotid canal transmit and where is it?
located posteriorly and medially to the foramen ovale
Internal carotid artery
Deep petrosal nerve
What junction does the foramen lacerum mark and what is it filled with in life?
sphenoid, temporal and occipital bones
filled with cartilage, only pierced by small blood vessels
What bones make up the posterior cranial fossa?
the occipital bone and the two temporal bones
What does the posterior cranial fossa accommodate?
accommodates the brainstem and cerebellum
What is the internal acoustic meatus and where is it? (what does it transmit)
oval opening in the posterior aspect of petrous part of temporal bone
Transmits facial nerve (CN VII), vestibulocochlear nerve (CN VIII) and labyrinthine artery
What does the foramen magnum transmit and where is it?
lies centrally in the floor of the posterior cranial fossa
the largest foramen in the skull
transmits the medulla of the brain, meninges, vertebral arteries, spinal accessory nerve
What does the jugular foramina transmit and where are they?
situated either side of the foramen magnum
Each transmits the
- glossopharyngeal nerve, vagus nerve, spinal accessory nerve (descending)
- internal jugular vein
- inferior petrosal sinus, sigmoid sinus
- meningeal branches of the ascending pharyngeal and occipital arteries
Where is the hypoglossal canal and what does it transmit?
Immediately superior to the anterolateral margin of the foramen magnum
It transmits the hypoglossal nerve through the occipital bone
What divides the cerebellar fossae?
divided medially by a ridge of bone, the internal occipital crest
What is responsible for superior eyelid movement?
Levator palpebrae superioris
Where does the levator palpebrae superioris attach?
Originates from the lesser wing of the sphenoid bone, immediately above the optic foramen
It attaches to the superior tarsal plate of the upper eyelid
What is the innervation of the LPS?
innervated by the oculomotor nerve (CN III)
What are the 4 recti muscles of eye?
superior rectus
inferior rectus
medial rectus
lateral rectus
Where do the 4 recti eye muscles originate from?
common tendinous ring at back of orbit
What is superior rectus’ innervation and role in the eye?
Oculomotor nerve (CN III)
Upward movement
What is inferior rectus’ innervation and role in the eye?
Oculomotor nerve (CN III)
Downward movement
What is medial rectus’ innervation and role in the eye?
Oculomotor nerve (CN III)
Adduction
What is lateral rectus’ innervation and role in the eye?
Abducens nerve (CN VI)
Abducts the eye
Where does the superior oblique originate from and attach to?
Originates from the body of the sphenoid bone at posterior orbit
Its tendon passes through a trochlear and then attaches to the sclera of the eye, posterior to the superior rectus
Where does the inferior oblique originate from and attach to?
Originates from the anterior aspect of the orbital floor
Attaches to the sclera of the eye, posterior to the lateral rectus
What is the role of the superior oblique in the eye and its innervation?
Depresses, abducts and medially rotates the eyeball
Trochlear nerve (CN IV)
What is the role of the inferior oblique in the eye and its innervation?
Elevates, abducts and laterally rotates the eyeball
Oculomotor nerve (CN III)
What can the outer ear be divided into?
External acoustic meatus
Pinna (auricle)
What can the outer ear be divided into?
External acoustic meatus
Pinna (auricle)
What is the function of the pinna?
capture and direct sound waves towards the external acoustic meatus
What is the tympanic membrane?
a connective tissue structure
attached to malleus
articulates to incus
Where is the middle ear?
within the temporal bone
extends from the tympanic membrane to the lateral wall of the inner ear
What is the function of the middle ear?
transmit vibrations from the tympanic membrane to the inner ear via the auditory ossicles
What are the 3 auditory ossicles (bones)?
the malleus (largest, most lateral), incus and stapes (smallest)
What do the ossicles link and why?
linking the tympanic membrane to the oval window of the internal ear
transmit sound vibrations
What does the stapedius muscle attach to and what is its innervation?
attaches to the stapes, and is innervated by the facial nerve.
What is tensor tympani attached to and what is it innervated by?
attaches to the handle of malleus, pulling it medially when contracting
innervated by the tensor tympani nerve, a branch of the mandibular nerve
What is the function of the inner ear?
- To convert mechanical signals from the middle ear into electrical signals, which can transfer info to the auditory pathway in the brain
- To maintain balance by detecting position and motion
Where is the inner ear?
located within the petrous part of the temporal bone
It lies between the middle ear and the internal acoustic meatus
Which 3 bones make up the bony labyrinth of the inner ear and which fluid is inside them?
composed of the cochlea, vestibule and three semi-circular canals
perilymph fluid
What is the innervation of the inner ear and how does the nerve divide?
vestibulocochlear nerve (CN VIII)
enters the inner ear via the internal acoustic meatus, where it divides into the vestibular nerve (responsible for balance) and the cochlear nerve (responsible for hearing)
Which nerve passes through inner ear but doesn’t innervate it?
Facial CN VII
Where is white and grey matter?
White matter in deeper parts of brain
Grey matter on cerebral cortex surface
What are sulci and gyri?
sulci (grooves or depressions)
gyri (ridges or elevations)
What divides the two hemispheres?
the longitudinal fissure
Where and what is the falx cerebri?
an arched crescent of dura lying in longitudinal fissure
What does the central sulcus separate?
frontal and parietal lobes
What does the lateral sulcus separate?
frontal and parietal lobes from the temporal lobe
Where is the precentral gyrus and what is it for?
directly anterior to central sulcus
location of primary motor cortex
Where is the postcentral gyrus and what is located there?
directly posterior to central sulcus
location of primary somatosensory cortex
Where is the superior temporal gyrus and what is it responsible for?
ridge located inferior to lateral sulcus
responsible for the reception and processing of sound
What are the functions of the meninges?
Provide a supportive framework for the cerebral and cranial vasculature
Acting with cerebrospinal fluid to protect the CNS from mechanical damage
Where is the dura mater?
directly underneath the bones of the skull and vertebral column
What are the two layers of the dura?
Outer periosteal of cranial dura line the interior of the skull, sends blood vessels and fibrous processes into the cranial bone
Inner meningeal layer completely envelopes CNS, tube of dura seen around spinal cord and tubular sheaths for cranial nerves
Are the dura layers fused?
The periosteal dura and meningeal dura are tightly fused together, except in a few places where they separate to form the dural venous sinuses
What is the dura mater like?
thick, tough, and inextensible
Where are the dural venous sinuses and what are they responsible for?
located between the two layers of dura mater
Responsible for the venous drainage of the cranium and empty into the internal jugular veins
What is the blood supply to the dura and what is its innervation?
primarily from the middle meningeal artery and vein
innervated by the trigeminal nerve (V1, V2 and V3)
Where do the dural folds come from and what is in them?
The meningeal layer of dura mater folds inwards upon itself to form four dural folds
Project into the cranial cavity, dividing it into several compartments – each of which houses a subdivision of the brain
What are the four dural folds?
Falx cerebri
Tentorium cerebelli
Falx cerebelli
Diaphagma sellae
How many venous sinuses are in the brain?
11
Which sinuses are in the falx cerebri?
straight, superior, and inferior sagittal sinuses
Where do the internal cerebral veins run?
Within substance of brain tissue and end at surface where they become external
Where do external cerebral veins run?
Surface of the brain, crossing subarachnoid space to drain into dural venous sinuses
What do sinuses in the brain do?
Connect major cerebral veins to internal jugular veins
Where can you find the cavernous sinus and what does it drain?
drains the ophthalmic veins and can be found on either side of the sella turcica. From here, the blood returns to the internal jugular vein via the superior or inferior petrosal sinuses
What is clinically significant about the cavernous sinus?
Contains 5 cranial nerves and the internal carotid artery
Very close to pituitary gland
What is the arachnoid mater?
the middle layer of the meninges, lying directly underneath the dura mater
What are 3 features of the arachnoid mater?
layers of connective tissue
avascular
does not receive any innervation
How does CSF re enter circulation?
Small projections of arachnoid mater into the dura (known as arachnoid granulations) allow CSF to re-enter the circulation via the dural venous sinuses
What do the sub-arachnoid cisterns contain?
CSF
What is CSF?
a clear, plasma-like fluid, that circulates within the system of cavities found within the central nervous system
Which specialized tissue produces and secretes CSF?
Choroid plexus
Where is the pia mater?
underneath the sub-arachnoid space
Features of the pia
very thin
tightly adhered to the surface of the brain and spinal cord
Follows gyri and sulci
Highly vascularised
What makes up the brainstem?
Medulla oblongata
Pons
Midbrain
What are the boundaries of the medulla?
beginning at the foramen magnum to the caudal border of the pons and bulbopontine sulcus
What are the 3 sulci/fissure of the anterior medulla?
ventrolateral sulcus
anterior median fissure
posterolateral sulcus
What and where are the pyramids of the medulla?
Paired swellings found between the anterior median fissure and the ventrolateral sulcus
Marks the position of the corticospinal tracts
Where are the olives in the medulla?
pair of swellings located laterally to the pyramids
between the ventrolateral and posterolateral sulci
Which CN extends out of the ventrolateral sulcus?
Hypoglossal CN XII
Which CN join the medulla in the posteriolateral sulcus?
CN IX, CN X, and CN XI
What are the olives?
caused by the presence of the underlying inferior olivary nucleus
concerned with the control of movement