Anatomy Flashcards
What is a group of nerve cell bodies in the CNS called and how is this named differently in the PNS?
CNS - Nucleus
PNS - ganglion
How can you tell the difference between an axon and the dendrites of a multipolar neuron?
Usually axon = longest process
What type of signals are usually transported via MULTIPOLAR neurons?
Motor efferent signals
What type of signals are usually transported via pseudounipolar neurons?
Sensory afferent signals
A nerve is a bundle of what?
Axons
this is called a tract in the CNS
Tracts tend to be of a “single modality”. What does this mean?
all axons contained within it have the same job
i.e. somatic motor/sensory, special sensory etc
What is meant by “mixed modality” nerves?
Axons for somatic motor and sensory and sympathetic all together in one nerve
What cranial nerves connect to the CNS in the forebrain?
CN I and CN II
What cranial nerves connect to the CNS via the midbrain?
CN III and CN IV
Where does CN V connect to the CNS?
Pons
What cranial nerves connect to the CNS at the pons-medullary junction?
VI, VII, VIII
Which of CN IX, X XI and XII does NOT connect to the CNS at the medulla?
CN XI connects at the spinal cord (SPINAL ACCESSORY NERVE)
Spinal nerves are actually very small. TRUE/FALSE?
TRUE - they are only found in the intervertebral foraminae as on one side they are rootlets/roots OR the opposite side = rami
What do the anterior and posterior rami supply?
Body walls (soma)
Are roots and rootlets single or mixed modality?
Single modality
Posterior rootlets/roots = somatosensory
Anterior rootlets/roots = somatomotor
Are spinal nerves and rami single or mixed modality?
Mixed modality
Anterior and Posterior roots come together and mix forming spinal nerve
What is the name given to the swelling on the posterior (or dorsal) root? And what does it contain?
Dorsal root ganglion
- contains a collection of cell bodies)
Rami supply what in their segment of the body?
- sensory supply to area
- somatic motor supply to skeletal muscles
- sympathetic supply to the skin and to the smooth muscle of arterioles
What is a dermatome?
area of skin supplied with sensory innervation from a single spinal nerve
e.g. T4 dermatome (nipple level)
What is a myotome?
skeletal muscles supplied with motor innervation from a single spinal nerve
Myotomes lie under the corresponding spinal nerve dermatome. TRUE/FALSE?
FALSE - this is not always the case
e.g. C3,4,5 dermatome = shoulder and upper arm
BUT myotome = diaphragm
Dermatomes for spinal nerves can overlap. TRUE/FALSE?
TRUE
Why is dermatome overlap a clinical issue?
If patient experiences a symptom (e.g. numbness/tingling) in a specific dermatome then we must contemplate that nerves in adjacent dermatomes may also be damaged
What dermatome levels mark the nipple and the umbilicus?
T4- nipple
T10 - umbilicus
Roughly describe what each segement of spinal nerves innervates (I.e. cervical,thoracic, etc)
Cervical - Upper limbs, posterior neck and head
Thoracic - thorax
Lumbar - anterior of lower limbs
Sacral - posterior of lower limbs
What makes up a nerve plexus?
ANTERIOR RAMI
What anterior rami make up each plexus?
Cervical C1-C4
Brachial C5-T1
Lumbar L1-L4
Sacral L5-S4
Its is possible for more than one named cutaneous nerve to pass through 1 dermatome. TRUE/FALSE?
TRUE
e.g. lateral cutaneous nerve of thigh, femoral nerve and obturator nerve ALL pass through L2 dermatome
Between what spinal levels does sympathetic outflow leave the spinal cord?
T1-L2
What extra horns are found in the spinal cord where sympathetics or sacral parasympathetics leave?
Lateral horns (on edge of grey matter in spinal cord)
What 4 ways are used by sympathetics to leave the spinal cord?
1) Signal ascends sympathetic chain before synapsing
2) Signal synapses on same spinal level it leaves
3) Signal descends sympathetic chain before synapsing
4) Passes through symp. chain without synapsing, passes onto splanchnic nerves and then synapses onto viscera
What term is used to describe parasympathetic outflow and why is this?
Craniosacral Outflow
- cranial nerves III, VII, IX and X
- sacral spinal nerves
What is the difference between the extrinsic and intrinsic muscles of the back?
Extrinsic attach outwith back
- attach back to pectoral girdle
- move upper limb
Intrinsic attach within the spine
- Maintain posture
- Superficial - Erector Spinae
- Deep muscles - Tranversospinalis
Strain of which muscle may cause lower back pain?
erector spinae strain
What nerves supply the extrinsic vs the intrinsic muscles?
Extrinsic = Anterior rami Intrinsic = Posterior rami
What movement is created if erector spinae contracts unilaterally?
Lateral flexion
Why do vertebrae get larger towards the lumbar region and then progressively smaller again
Larger to bear more weight
UNTIL weight has transferred to hip bones
What curves of the spine are considered SECONDARY? (AKA not present from birth, they have adapted to new functions of the spine)
Cervical and Lumbar Lordosis
Where are spinal nerves found and where is the spinal cord found in relation to the vertebrae?
Spinal nerves = intervertebral foramen
Spinal cord = vertebral foramen
What ligaments are found on the outside of the vertebral body?
posterior longitudinal ligament (between body and spinal cord)
anterior longitudinal ligament (wider and gives more support)
What ligament attaches between adjacent vertebrae?
ligamentum flavum
Where are the supraspinous ligament and interspinous ligament found?
supraspinous ligament = connects tips of spinous processes
(Strong)
interspinous ligament
connects adjacent spinous processes
(weak)
What features are typical of the cervical vertebrae?
- transverse foramen
- bifid spinous process
- triangular shaped vertebral foramen
C1 does not have a body or spinous process. TRUE/FALSE?
TRUE
body is donated to C2 as odontoid process
Why is C7 important?
first palpable spinous process in ~70% of people
How does C1- Atlas connect to the base of the skull
Connection between occipital condyles and the superior articular facets of the atlas
- synovial joints for maximum movement
What movements does the Atlanto-occipital joint allow?
Flexion, extension
Little lateral flexion and rotation
How many articulations are part of the Atlanto-axial joint?
3 articulations – all synovial
What is the main function of the atlanto-axial joint?
Rotation
C1 disappears on a radiograph as it has no spinous process. TRUE/FALSE?
FALSE
the posterior arch appears like a spinous process would
It is easier to fracture cervical vertebrae than dislocate them. TRUE/FALSE?
FALSE
much easier to dislocate them
Sometimes they will reduce by themselves
What nerves pass through the anterior and posterior sacral foraminae?
Rami of spinal nerves
What is the cauda equina made up of?
Nerve roots from L2 -> Co1 descending to their intervertebral foramen at their level
Why is it safer to perform an epidural or lumbar puncture at the level of the cauda equina?
No damage to the spinal cord
Nerve roots more likely to move out of way of needle
What can result from an epidural or lumbar puncture which damages the venous plexus in the epidural fat?
Epidural haematoma which can compress the spinal cord
What layer of meninges needs to be reached during a lumbar puncture?
Subarachnoid space containing CSF for extraction
What is a laminectomy?
Removal of one or more spinous processes and the adjacent lamina
What functions are defined as special sensory?
Sight Smell Taste Hearing Balance
CN I only has a special sensory function. TRUE/FALSE?
TRUE
Only special sensory for smell
What is the extracranial part of CN I?
bipolar neurons in the olfactory mucosa of nasal cavity
What cranial foraminae does CN I pass through?
Cribriform plate of the ethmoid bone
In the Anterior cranial fossa
What part of CN I is intracranial?
olfactory bulb and tract
Is CN II sensory or motor?
Special sensory - sight
Where does CN II appear extracranially?
Neurons in retina connect to optic nerve at back of orbit
What cranial foraminae does CN II pass through?
optic canal
In the middle cranial fossa
What part of CN II is found intracranially?
optic chiasm joins to form the optic tract.
Does CN II connect to the CNS?
Yes connects at Diencephalon/ Thalamus
How is CN I clinically tested?
Get patient to smell a familiar smell while covering the contralateral nostril.
e.g. Orange/lemon peel, coffee or vinegar
How is CN II clinically tested?
5 Ways: Acuity (Snellen charts) Colour Fields Reflexes (this also tests efferent limb of reflex though!) Fundoscopy
Is CN III sensory or motor, and what are its functions?
Motor (moves eyes)
Parasympathetic (motor) for pupil constriction
Where does CN III connect with the CNS?
Midbrain (mesencephalon)
Where does CN III travel intracranially when attempting to reach the eye?
Towards the orbit in the lateral wall of the cavernous sinus, through the common tendinous ring
Through which cranial foraminae does CN III pass through, and what other nerves also pass through here?
Superior orbital fissure
CN IV, V1 and VI
Where does CN III end up extracranially?
Passes into orbit and supplies ALL extraocular muscles except two.
Parasympathetics synapse in ciliary ganglion
Where does the trochlear nerve communicate with the CNS?
Midbrain (mesencephalon)
Is CN IV sensory or motor?
Motor (moves Superior oblique muscle in eye)
What course is taken by CN IV intracranially?
Travels towards the orbit in the lateral wall of the cavernous sinus, but does NOT pass through common tendinous ring
How are CN III and IV different in they wa they innervate the muscles of the eye?
CN III passes through common tendinous ring to innervate from deep to the muscles
CN IV does ONT pass through ring, and instead sits on top of Superior oblique to innervate
Is CN VI sensory or motor, and what is its main function?
Motor to Lateral rectus
=> abducts the eye
Where does CN VI meet the brainstem?
Pontomedullary junction
What course does CN VI take intracranially?
Travels towards the orbit within the cavernous sinus.
similar to CN III
Other than CN III and VI, what other structure travels towards the orbit in the cavernous sinus?
Ophthalmic artery
Where does CN VI appear extracranially?
Found in orbit supplying only the lateral rectus muscle.
How can each ocular muscle be isolated to test the cranial nerves?
The “H” Test
What is the function of CN VIII?
Special Sensory (Hearing and Balance)
Where is CN VIII found extracranially?
Axons from cochlear and vestibular apparatus.
Which of the cranial foraminae does CN VIII pass through? What other nerve passes through here?
Internal acoustic meatus
(In posterior cranial fossa)
- CN VI also passes through here
Where does CN VIII meet the CNS?
pontomedullary junction
How is CN VIII clinically tested?
Rinne and Weber tests
(Rinne's = tuning fork on mastoid process for conductive hearing loss) (Weber's = tuning fork on forehead for Sensorineural Hearing loss)
CN XI has a motor supply to which two muscles?
Sternocleidomastoid and Trapezius
Where does CN XI connect to the CNS?
Connection with the CNS:
Cervical spinal cord (C1-4/5)
Cranial foramina:
Jugular Foramen
In posterior cranial fossa
Extracranial part:
Axons supply SCM on deep surface, then continue across the posterior triangle to supply trapezius and SCM
Describe the intracranial course of CN XI, and the cranial foramina from which it exits the skull
- Ascends through foramen magnum from spinal cord
- Travels towards jugular foramen to exit with CN IX and X
Describe the extracranial course of CN XI
Axons supply sternocleidomastoid on deep surface
Then travel across the posterior triangle to supply trapezius
How can CN XI be clinically tested?
Ask patient to shrug shoulders to test TRAPEZIUS
Ask them to flex neck and turn towards the opposite side => STERNOCLEIDOMASTOID
If a patient has trapezium weakness but the sternocleidomastoid is intact, where may the damage/lesion be located?
After CN XI passes through posterior triangle, as it has already supplied SCM by this point
Is CN XII sensory or motor? What does it supply?
Motor to muscles of the tongue
Where does CN XII connect to the CNS?
In groove between pyramids and olives of the medulla
What cranial foraminae does CN XII use to exit?
Hypoglossal Canal
Describe the extracranial course of CN XII?
Descends lateral to carotid sheath.
At the level of the hyoid loops around occipital artery to change direction and supply tongue
Which of the tongue muscles does CN XII not innervate?
palatoglossus.
How can CN XII be clinically tested?
- Ask patient to stick tongue straight out
- If unilateral CN XII pathology the tongue tip will point TOWARDS the side of the injured nerve
Where does CN V connect to the CNS?
Pons
only one that connects here
What cranial foraminae are used by the divisions of CN V?
V1 -Superior orbital fissure
V2- Foramen rotundum
V3- Foramen ovale
What structures are found in the CN V1 dermatome?
- upper eyelid
- cornea (corneal reflex)
- conjunctiva
- Skin of the root/bridge/tip of the nose
What is covered by the CN V2 dermatome?
From the skin of the lower eyelid over the maxilla to the upper lip
What structures are covered by the CN V3 dermatome?
Skin over the mandible and TMJ
What deeper structures do the trigeminal divisions supply under their dermatomes?
V1 - Bones & soft tissues of the orbit, anterior nasal cavity
V2 - posterior nasal cavity, maxillary sinus, upper dental arch
V3 - Mandible, Floor of the mouth, Buccal mucosa, lower dental arch
What larger muscles does CN V3 supply and what is their main function?
Muscles of mastication: **CLOSE** Masseter Temporalis Medial Pterygoid
OPEN
Lateral pterygoid
What two small muscles are supplied by CN V3 and what are their functions?
Tensor veli palatini - tenses palate
Tensor tympani - muffles sounds
How is the sensation of the CN V1,2,3 dermatomes tested?
brush the skin in each dermatome with a fine tip of cotton wool
How is the motor function of CN V3 tested?
- Palpate the contraction of masseter & temporalis by asking patient to clench teeth
- Ask the patient to open their jaw against resistance
Is CN VII sensory or motor?
Special Sensory (Taste), Motor AND parasympathetics
How does CN VII enter and exit the cranium?
IN - Internal Acoustic Meatus
OUT - Stylomastoid foramen
Describe the extracranial course of CN VII
- Somatic motor axons pass into the parotid gland
- Then form 6 branches supplying muscles of facial expression
What part of the CN VII course does the chorda tympani arise from?
Splits off from CN VII in facial canal
Found in temporal bone
AT posterior surface of the middle ear
What does the chorda tympani go on to supply?
- Taste - anterior 2/3rds of the tongue
- Parasympathetic - salivary glands
What is the smallest muscle in the body, which is supplied by CN VII, and what is the function of this muscle?
Stapedius
- Reduces stapes movement to protect the internal ear from excessive noise
What nerve does the Chorda tympani piggy back on, in order to supply the salivary glands and the tongue?
Lingual nerve (division of V3)
What muscles of facial expression does CN VII supply?
Frontalis (forehead)
Orbicularis oculi
Elevators of lips
Orbicularis oris
How are the muscles of facial expression used to test CN VII?
Raise eyebrows (frontalis)
Close eyes tightly (orbicularis oculi)
Smile (lip elevators)
Puff out cheeks and hold air (orbicularis oris)
What are the many functions of CN IX?
Special sensory (vallate papillae - Taste)
Sensory
- posterior 1/3rd of the tongue
- pharynx
- palatine tonsil
- eustachian tube and middle ear
Motor - stylopharyngeus
Visceral afferent - carotid sinus
Parasympathetic (motor) - parotid gland
Describe the extracranial course of CN IX in order to complete all of its functions
Descends towards pharynx and mouth
Describe the extracranial structures supplied by the vagus nerve CN X?
Axons supply lots of structures BETWEEN the palate and the midgut
The vagus nerve runs just lateral to the carotid sheath. TRUE/FALSE?
FALSE
CN XII runs just lateral to the sheath
whereas CN X runs within the carotid sheath
What does the vagus nerve curve under on either side?
Left curves under arch of aorta
Right curves under subclavian
How is the vagus nerve transported to the structures in the gut?
On arteries
How can CN X be clinically tested?
- Ask patient to say ‘ahhhhh’ - tests MUSCLES OF PALATE
- Ask patient to swallow small amount of water - tests PHARYNGEAL MUSCLES
- Listen to speech - tests LARYNGEAL MUSCLES
Why are space occupying lesions (SOL) such a problem in the skull?
- Not a lot of extra space
- Can cause raised Intracranial Pressure (ICP)
- Contents can be compressed or attempt to herniate
What are the 5 layers of the scalp?
S = Skin C = Connective tissue A = Aponeurosis L = Loose connective tissue P= Pericranium
Which layer of the scalp contains the anastomotic network of arteries?
C = Connective tissue
Why does the scalp tend to bleed a lot when injured?
Connective tissue layer housing blood vessels is very sturdy and holds vessels open when they are cut into
What is thought to be the weakest point in the skull, and what artery is found deep to this area?
Pteryion
(where frontal, parietal, temporal and sphenoid bones meet and have an H shaped suture)
Middle meningeal artery found behind this
The dura mater has two layers. What are these layers called, and what can arise between them?
Periosteal layer - over bone
Meningeal layer - over arachnoid layer
dural venous sinuses form between them
A fracture of the skull is likely to penetrate through a suture. TRUE/FALSE?
FALSE
sutures stop the propagation of fractures in the skull
The middle meningeal artery creates a groove in the base of the skull that leads to which foramina?
Foramen spinosum
Where does the pain in meningitis arise from, and why?
Stretching of the dura mater
dura is only meningeal layer with sensory innervation
What are arachnoid granulations from the arachnoid mater?
projections up into the dural venous sinuses which reabsorb CSF
What layer of the dura mater does not extend down to the spinal cord?
Periosteal - as no part is needed to cover bone
What tough sheet of dura mater forms a roof over the pituitary fossa?
diaphragm sellae
What name is given to the sheet of dura mater which covers the cerebellum ?
Tentorium Cerebelli
What is the Falx cerebri?
infolding of 2 dura mater layers in lilne with sagittal suture
Attaches to crista galli anteriorly and merges with tentorium cerebelli posteriorly
How does blood from the cerebral hemispheres of the brain drain to the dural venous sinuses?
Cerebral veins
What is a secondary function of the dural venous sinuses?
reabsorb CSF from arachnoid granulations
Why is an infection to the facial vein (superficial) rather dangerous?
Can track back to cavernous sinus in brain and cause infection
What artery does the vertebral artery branch from?
The subclavian artery
What are the main arteries in the Circle of Willis supplying the cerebrum?
Anterior Middle and Posterior cerebral arteries
In what layer of the meninges is the Circle of Willis found?
Subarachnoid space => its bathed in CSF
When would damage to the Circle of Willis or one of its branches be suspected?
If blood was found in the CSF
Describe the course of CSF from production to the subarachnoid space (and a little to centre of spinal canal)
Made in choroid plexus Lateral ventricles -> foramina of Monro -> 3rd ventricle -> cerebral aqueduct -> 4th ventricle -> subarachnoid space
What 3 situations can cause hydrocephalus?
- Overproduction
- Flow obstruction
- Inadequate reabsorption
What intervention can be done in children for hydrocephalus?
ventricular peritoneal shunt
moves CSF reabsorption point down into peritoneum
Where is it possible to bleed in the cranial cavity and what can cause this?
EXTRADURAL
- between bone and dura
- ruptured middle meningeal artery
SUBDURAL
- separates the dura from the arachnoid
- torn cerebral veins
SUBARACHNOID
- bleed into the CSF of subarachnoid space
- ruptured Circle of Willis (“berry”) aneurysm
How can parts of the brain herniate if there is raised ICP?
- *Parts ABOVE tentorium cerebelli**
1. Subfalcine - can move under falx cerebri
2. Central - move over the tentorium cerebelli
3. Trancalvarial - move out through fractured bone
4. Uncal - moves down towards tentorium cerebelli - *Parts UNDER tentorium cerebelli**
1. Upward cerebellar - move towards tentorium cerebelli
2. Tonsillar - Cerebellum moves downwards
