Case 5 anatomy Flashcards
the cribriform plate is part of which bone?
ethmoid bone
where does the optic nerve terminate?
in the lateral geniculate nucleus
where does the trochlear nerve arise from?
the dorsal surface of the midbrain
describe the course of the trochlear nerve
- Arises from the dorsal surface of the midbrain
- Passes anteriorly around the brainstem
- Pierces the dura mater at the margin of the tentorium cerebelli
- Passes in the lateral wall of the cavernous sinus
- Exits the skull through the superior orbital fissure and enters the orbit
which nerves arise from the midbrain?
- oculomotor
- trochlear
which nerves arise from the pons?
trigeminal
where do you find the trigeminal ganglion?
on the anterior surface of the petrous temporal bone
describe the course of the ophthalmic branch
- Passes forwards in the lateral cavernous sinus
* Divides into three branches which exit the skull through the superior orbital fissure to enter the orbit
where does the maxillary branch exit the skull? where does it go next?
through the foramen rotundum
- Enters the pterygopalatine fossa
- It gives off numerous branches within the pterygopalatine fossa
what’s the terminal branch of the maxillary nerve? where does it go?
Its terminal branch, the infraorbital nerve, exits the fossa through the inferior orbital fissure to enter the orbit
where does the mandibular branch exit the skull?
through the foramen ovale
where does the manibular branch give off its branches?
in the infratemporal fossa
what are the branches of the ophthalmic branch?
- Frontal
- Nasociliary
- Lacrimal
(FML)
what are the branches of the maxillary branch?
- Infraorbital
- Zygomatic
- Nasopalatine
- Greater palatine
- Lesser palatine
- Anterior superior alveolar
- Middle superior alveolar
- Posterior superior alveolar
what are the branches of the mandibular branch?
- Meningeal
- Deep temporal
- Auriculotemporal
- Masseteric
- Nerve to medial pterygoid
- Buccal
- Incisive
- Lingual
- Inferior alveolar
- Mental
- Nerve to mylohyoid
what is the sensory distribution of the different branches of the trigeminal nerve?
- Ophthalmic = forehead and backwards, eyebrows and medial part of nose
- Maxillary = up to forehead, over cheek bone, lateral parts of nose
- Mandibular = up to forehead, across side of cheeks, over chin
what are the muscles that the mandibular division provides innervation to?
8 muscles:
• Four muscles are the muscles of mastication; masseter, temporalis, medial pterygoid and lateral pterygoid
• Anterior belly of digastric, mylohyoid, tensor tympani, tensor veli palatini are also innervated by mandibular nerve
what does the tensor veli palatini do?
tenses the soft palate
what innervates the stapedius muscle?
facial nerve
which nerves arise from the pons-medullary junction?
abducent, facial and glossopharyngeal nerves
describe the pathway of the abducent nerve
- Arises from the brain stem at the pons-medullary junction
- Traverse the pontine cistern of the subarachnoid space
- Pierces the dura mater at the clivus
- Passes through the cavernous sinus parallel to the internal carotid artery
- Exits the skull through the superior orbital fissure and enters the orbit
which cranial nerve runs parallel to the internal carotid artery in the cavernous sinus?
abducent nerve
what are the functions of the facial nerve?
- motor innervation to the muscles of facial expression
- taste sensation from the anterior 2/3 of the tongue
- cutaneous sensation for the external ear
- parasympathetic innervation to the nasal glands, lacrimal gland, and submandibular & sublingual salivary glands
which cranial nerve nuclei is the facial nerve associated with?
4
• Trigeminal – the nucleus where facial nerve fibres carrying general sensation terminate
• Rostral end of nucleus solitarius – the nucleus where facial nerve fibres carrying taste sensation terminate
• Facial motor nucleus – the nucleus where lower motor neurones supplying the muscles of facial expression arise
• Superior salivatory nucleus – the nucleus where preganglionic parasympathetic fibres to the lacrimal, nasal, submandibular and sublingual glands arise
what is the facial nerve composed of?
the facial nerve proper and the nervus intermedius:
- The facial nerve proper is the somatic motor component which supplies the muscles of facial expression
- The nervus intermedius is composed of the sensory and parasympathetic components
what ganglion is associated with the facial nerve?
geniculate nucleus
through what does the facial nerve leave the skull? (which fibres?)
stylomastoid foramen - general sensory and motor fibres
describe the course of the facial nerve and branches that it gives off
- Passes through the posterior cranial fossa
- Enters the petrous temporal bone through the internal auditory meatus
- As it passes through the facial canal it swells to form the geniculate ganglion
- The greater petrosal nerve and the nerves to the stapedius and the chorda tympani are given off
- The general sensory and motor fibres exit the skull through the stylomastoid foramen
what does the greater petrosal nerve do? what fibres does it transmit?
- Transmits general visceral efferent fibres? (superior salivatory nucleus)
- Provides presynaptic fibres to the pterygopalatine ganglion
- Postganglionic parasympathetic fibres from the pterygopalatine ganglion provide secretomotor innervation to the lacrimal and nasal glands
nerve to stapedius
- what fibres does it transmit
- what might a lesion lead to
- Transmits special visceral efferent fibres (facial motor nucleus)
- A lesion of the nerve to stapedius may result in hyperacusis (increased sensitivity to certain frequencies and volume ranges of sound)
chorda tympani
- what’s its course
- what fibres does it transmit
- Transmits both special visceral afferent fibres and general visceral efferent fibres
- Exits the tympanic cavity through the petrotympanic fissure
- Joins the lingual nerve in the infratemporal fossa
- Provides parasympathetic innervation to the submandibular and sublingual glands
what branches does the facial nerve give off after leaving the stylomastoid foramen?
- As the facial nerve exits the stylomastoid foramen it gives of general sensory fibres to supply a small area of skin around the concha of the auricle
- Close to the stylomastoid foramen it gives off motor branches to the stylohyoid muscle and the posterior belly of the digastric
- The remainder of the nerve passes forward to enter the substance of the parotid gland where it divides into the five main motor branches; temporal, zygomatic, buccal, mandibular, cervical
what fibres does the vestibulocochlear nerve transmit?
special somatic afferent fibres
what are the functions of the glossopharyngeal nerve?
- initiates the swallowing reflex in response to general stimulation of the oropharynx
- transmits both general and taste sensation from the posterior 1/3 of the tongue
- forms the afferent limb of the gag reflex
- transmits parasympathetic fibres to the parotid salivary glands
- provides motor innervation to the stylopharyngeus muscle
what are the cranial nerve nuclei that the glossopharygneal nerve are associated with?
5
• Trigeminal nucleus – the nucleus where glossopharyngeal nerve fibres carrying general sensation terminate
• Nucleus solitarius – the nucleus where visceral afferent fibres from the carotid sinus and bodies terminate
• Rostral end of nucleus solitarius – the nucleus where visceral afferent fibres carrying taste sensation terminate
• Inferior salivatory nucleus – the nucleus where preganglionic parasympathetic fibres to the parotid gland arise from
• Nucleus ambiguus – the nucleus where lower motor neurones supplying the stylopharyngeus arise from
which cranial nerves arise from the medulla?
glossopharyngeal, vagus, accessory (not spinal) and hypoglossal nerves
where does the glossopharyngeal nerve arise?
lateral aspect of the medulla between the olive and inferior cerebellar peduncle
describe the course of the glossopharygneal nerve
- Arises from the lateral aspect of the medulla between the olive and inferior cerebellar peduncle
- Passes through the posterior cranial fossa
- Exits the skull at the jugular foramen
- Follows the course of the stylopharyngeus muscle
- Passes between the superior and middle constrictor muscles to enter the oropharynx
which nerves pass though the jugular foramen?
glossopharyngeal, vagus and accessory nerves
where are the nerve cell bodies of the primary order neurons of the glossopharygneal nerve?
superior and inferior ganglia of the glossopharyngeal nerve are located near the jugular foramen
what’s the ganglion for the parotid gland?
otic ganglion
what are the functions of the vagus nerve?
- pharyngeal branches supply all the muscles of the soft palate except the tensor veli palatini and all the muscles of the pharynx except the stylopharyngeus
- laryngeal branches supply all the muscles of the larynx and provides sensory innervation to the larynx
- it’s therefore essential for the protective cough reflex
- provides parasympathetic innervation to the organs of the thorax and abdomen and conveys visceral afferent information from these regions
what are the muscles of the soft palate?
- tensor veli palatini
- levator veli palatini
- palatoglossus
- palatopharyngeus
- musculus uvulae
what are the cranial nerve nuclei that the vagus nerve is associated?
- Trigeminal nucleus – the nucleus where vagal fibres carrying general sensation terminate
- Nucleus solitarius – the nucleus where visceral afferent fibres from the thorax and abdomen terminate
- Rostral end of nucleus solitarius – the nucleus where vagal fibres carrying taste sensation terminate
- Dorsal motor nucleus of the vagus – the nucleus where preganglionic parasympathetic fibres to the organs of the abdomen and thorax arise from
- Nucleus ambiguus – the nucleus where lower motor neurons suppling the muscles of the soft palate, pharynx and larynx arise
describe the course of the vagus nerve
- Arises from the lateral aspect of the medulla between the olive and inferior cerebellar peduncle
- Passes through the posterior cranial fossa
- Exits the skull at the jugular foramen
- Passes through the neck in the carotid sheath
- Passes through the mediastinum behind the root of the lung
- Enters the abdomen through the oesophageal hiatus of the diaphragm
at what vertebral level does the vagus nerve pass through the diaphragm?
vagus nerve passes through the diaphragm at the level of the 10th thoracic vertebra (oesophageal hiatus)
what are the branches that the vagus gives off? describe their paths
- The vagus gives off pharyngeal branches high within the neck which contribute motor fibres to the pharyngeal plexus
- The superior laryngeal nerve consists of two branches: the internal laryngeal nerve (sensory), which supplies sensory fibres to the laryngeal mucosa, and the external laryngeal nerve (motor), which innervates the cricothyroid muscle
- The right recurrent laryngeal nerve hooks under the subclavian artery and passes back up the larynx between the trachea and oesophagus
- The left recurrent laryngeal nerve passes in front of the aortic arch, and then wraps underneath it and behind it
what does the internal laryngeal nerve supply?
sensory fibres to the laryngeal mucosa
what does the external laryngeal nerve supply?
motor fibres to cricothyroid muscle - tenses vocal cords, increasing pitch
describe the root of the spinal accessory nerve
- The spinal root of the accessory nerve arises from the upper 5-6 segments of the spinal cord
- It enters the skull through the foramen magnum and unites with the cranial root
- Exits the posterior cranial fossa through the jugular foramen
- The two roots separate and the cranial root joins the vagus nerve
- The spinal root pierces sternocleidomastoid and crosses the posterior triangle of the neck
what does the accessory nerve innervate?
trapezius and sternocleidomastoid muscles
what does the hypoglossal nerve innervate?
all muscles of the tongue except palatoglossus muscle
what is more anterior the vagus or hypoglossal nerve?
hypoglossal
where does the hypoglossal nerve arise from?
medulla between the pyramid and the olive
describe the course of the hypoglossal nerve
- Arises from the medulla between the pyramid and the olive
- Crosses the posterior cranial fossa and exits the skull through the hypoglossal canal
- In the neck it contributes to the ansa cervicalis
- It descends medial to the angle of the mandible and turns forward
- Passes between the mylohyoid and hyoglossus muscles
- Then lies lateral to the genioglossus muscle
what are the different glands, what are they innervated by and what ganglions?
greater petrosal nerve -> pterygopalatine ganglion -> lacrimal & nasal glands
chorda tympani (facial nerve) -> submandibular ganglion -> sublingual & submandibular glands
glossopharyngeal nerve -> otic ganglion -> parotid gland
which nucleus of the trigeminal sensory nucleus receives information from the mucosa of the larynx when it’s irritated by a foreign body?
chief nucleus - touch and pressure (and vibration)
what are the three horns of the spinal cord?
dorsal, lateral and ventral
how many regions is the grey matter further divided into? what are these regions referred to as?
10 - based on cytoarchitecture - Rexed’s laminae
1 to 10 going from dorsal to ventral
which regions of rexed’s laminae are known for what?
- laminae I - III = substantia gelatinosa - associated with nociception
- lamina VII = contians preganglionic autonomic neurones
- lamina IX = motor neurones that innervate skeletal muscle
what do the third order neurones ascend via to get to the somatosensory cortex?
internal capsule
in the lateral spinothalamic tract, where do second order neurones decussate?
within one segment of their origin
where does the lateral and ventral spinothalamic tract go to in the thalamus? how does it get there?
VP(L) nucleus
- axons pass to in the spinal lemniscus
what side to dorsal columns axons ascend in?
ipsilateral dorsal column
where do first order neurones of the dorsal columns terminate?
nucleus gracilis and nucleus cuneatus - in the medulla
what happens to second order neurones of dorsal columns?
- axons decussate
- ascend in medial lemniscus
- terminate in VP(L) nucleus of thalamus
in the ventral spinothalamic tract, where do second order neurones decussate?
they may ascend several segments before decussating
where do central fibres of the trigeminal nerve terminate?
trigeminal sensory nucleus
where does the trigeminal sensory nucleus extend from and to?
midbrain to cervical spinal cord
spinal nucleus extends from medulla to spinal cord
where are the facial nerve primary nerve cell bodies?
geniculate ganglion
where is the geniculate ganglion located?
in petrous temporal bone
where are the superior and inferior glossopharyngeal ganglia located?
close to jugular foramen
where are the superior and inferior (nodose) vasal ganglia located?
close to jugular foramen
where do axons of second order neurones from the trigeminal sensory nucleus decussate and ascend?
in the contralateral trigeminothalamic tract
where do axons of second order from the trigmenal sensory nucleus terminate?
VP nucleus
how do proprioception pathways differn from other sensory pathways of the head?
the nerve cell bodies of the primary neurones are located in the mesencephalic nucleus (i.e. the mesencephalic nucleus contains nerve cell bodies of primary neurones not secondary neurones)
what is the pyramidal tract?
corticospinal tract
describe the pathway of the UMNs of the corticospinal tract from the primary motor cortex to the brainstem.
- axons pass through the corona radiata
- then through the posterior limb of the internal capsule
- then through the midbrain in the crus cerebri
(this is similar for corticobulbar tract)
where do the axons of the corticospinal tract decussate and what happens next?
- 75-90& fibres decussate in medulla -> lateral corticospinal tract
- remaining fibres descend ipsilaterally in the ventral corticospinal tract - these fibres decussate near their termination
how are most cranial nerve motor nuclei innervated? how does this compare to spinal nerves?
- Lower motor neurones arising in the spinal cord are innervated by the contralateral corticospinal tract
- In contrast, most cranial nerve motor nuclei are bilaterally innervated
- This means that they receive innervation from both the contralateral and ipsilateral corticobulbar tracts
if there is a lesion in the hypoglossal nerve, how does tongue deviation differ depending on where the lesion is?
- If the muscles of the tongue are not working on one side the tongue will deviate to the side of weakness when protruded
- the tongue will deviate to the right if a patient has a lower motor neurone lesion of the right hypoglossal nerve
- the tongue will deviate to the left if the patient has an upper motor neurone lesion on the right side of the brain affecting fibres that synapse with the hypoglossal nerve
spinocerebellar tract
- what is it
- where information from
- involved in what
- ascending tract which carries information from muscle spindles, Golgi tendon organs and tactile receptors to the cerebellum
- involved in the control of posture and coordination of movement
spinoreticulothalamic (spinoreticular) tract
- what is it - pathway
- involved in
- ascending tract that arises in the spinal cord and ascends to the reticular formation
- reticulothalamic fibres ascend to the thalamus and synpase with thalamocortical fibres
- provides route by which dull aching pain is consciously recognised
- It is responsible for automatic responses to pain, such as in the case of injury.
rubrospinal tract
- what is it
- what is it involved in
- where afferent fibres from
- descending tract which originates from the red nucleus of the midbrain
- controls the tone of limb flexor muscles
- receives afferent fibres from the motor cortex and the cerebellum
what are pyramidal and extrapyramidal tracts? what is each involved with?
Pyramidal tracts – These tracts originate in the cerebral cortex, carrying motor fibres to the spinal cord and brain stem. They are responsible for the voluntary control of the musculature of the body and face.
Extrapyramidal tracts – These tracts originate in the brain stem, carrying motor fibres to the spinal cord. They are responsible for the involuntary and automatic control of all musculature, such as muscle tone, balance, posture and locomotion
tectospinal tract
- what is it
- where most fibres terminate
- what involved with
- descending tract which originates in the superior colliculus
- most fibres terminate in the cervical region of the spinal cord
- mediate reflex movements in response to visual stimuli
vestibulospinal tract
- what is it
- what control
- descending tract which originates in the vestibular nucleus
- controls extensor muscle tone and is involved in the maintenance of posture
reticulospinal tract
- what is it
- what involved in
- descending tract which originates in the retciular formation of the pons and medulla
- mediates the pressor and depressor effects of the cardiovascular system and the control of breathing
what is the reticular formation involved with?
- pain perception
- control of consciousness
- regulation of cardiovascular and respiratory systems
what is the superior colliculus involved in?
coordination of eye movements and eye reflexes
what is the inferior colliculus involved in?
coordination of auditory reflexes
what does the olivary nucleus have connections with and what’s it involved with?
- cerebellum
- control of movement
what is the crus cerebri?
a column of descending fibres located on the ventral surface of the midbrain
what nuclei are there in the sensory (afferent) category?
- General somatic afferent (GSA)
- Special somatic afferent (SSA)
- General visceral afferent (GVA)
- Special visceral afferent (SVA)
what nuclei are there in the motor (efferent) category?
- General somatic efferent (GSE)
- Special visceral efferent (SVE)
- General visceral efferent (GVE)
what terminates at the general somatic afferent nuclei?
general sensory fibres from the head and neck
what terminates at the special somatic afferent nuclei?
special sensory fibres of hearing and balance
what terminates at the general visceral afferent nuclei?
fibres from viscera, baroreceptors and chemoreceptors
what terminates at the special visceral afferent nuclei?
taste fibres
what do the general somatic efferent nuclei contain?
nerve cell bodies of lower motor neurones which supply skeletal muscle
what do general visceral efferent nuclei contain?
efferent neurones of the ANS that provide motor innervation to smooth muscle, cardiac muscle, and glands
what do special visceral efferent contain?
nerve cell bodies of motor neurones supplying skeletal muscle derived from pharyngeal arches
what are the GSA nuclei? what fibres terminate here?
trigeminal nucleus
- trigeminal, facial, glossopharyngeal and vagus nerve fibres
what are the SSA nuclei?
- cochlear nucleus
- vestibular nucleus
what are the GVA nuclei?
nucleus solitarius
what are the SVA nuclei?
rostral end of the nucleus solitarius
what are the GSE nuclei?
- oculomotor
- trochlear
- abducens
- hypoglossal
what are the SVE nuclei?
- trigeminal motor
- facial
- nucleus ambiguous
what are the GVE nuclei?
four parasymapthetic nuclei:
- Edinger-Westphal
- superior salivatory nucleus
- inferior salivatory nucleus
- dorsal motor nucleus of vagus
what nerves does the nucleus ambiguous supply fibres to?
glossopharyngeal and vagus nerves
what nerve is the superior salivatory nucleus associated with?
facial nerve
what’s the course of the facial nerve from the superior salivatory nucleus?
- preganglionic fibres project to the pterygopalatine ganglion
- synapse with postganglionic fibres that supply the lacrimal and nasal glands
- other preganglionic fibres synapse in the submandibular ganglion
- postganglionic fibres supply the submandibular gland and sublingual gland
what nerve is the inferior salivatory nucleus associated with?
glossopharyngeal nerve
describe the course of the glossopharyngeal nerve from the inferior salivatory nucleus
- preganglionic fibres synpase in the otic ganglion
- postganglionic fibres project to the parotid gland
