Lecture 1 Flashcards
How many cranial nerves do we have?
12
What are cranial nerves?
They are peripheral nerves that emerge from the brainstem before travelling through the tissues and foramina to the skull in order to reach their target organs.
Name cranial nerve X and state what is special about it
the vagus nerve
It is the only cranial nerve that leaves the head and neck regional’s
What does the vagus nerve supply?
structures of the head, neck, thorax and abdomen.
Name the 5th cranial nerve
The trigeminal nerve
What does the trigeminal nerve do?
The trigeminal nerve provides the general sensory nerve supply to ALMOST all of the structures of the mouth
Also provides the general sensory supply to a much wider area of the head, including the orbits, the nasal cavity, the paranasal air sinuses and most of the skin on the face and forehead.
What structures in the mouth does the trigeminal nerve not supply?
Some structures in the posterior aspect of the oral cavity, including the posterior part of the tongue (These are supplied by the glossopharyngeal nerve)
Where does the trigeminal nerve arise from?
The brain stem
Specifically the lateral aspects of the pos
What does the trigeminal nerve emerge as from the brainstem?
It emerges as two separate nerve roots
Name the 2 nerve roots the emerge from the brainstem to give the trigeminal nerve
the sensory and the motor roots of the trigeminal nerve.
Which root is bigger the sensory or motor root?
The sensory root is much bigger than the motor root.
What do the 2 nerve roots of the trigeminal nerve do once they have emerged from the brain stem?
The two roots run together, passing anteriorly through the posterior cranial fossa.
Name the 3 fossa we can see if we look inside someones head from above
- Anterior fossa
- Middle fossa
- Posterior fossa
What does the posterior fossa contain?
The foramen magnum
What happens at the foramen magnum?
The brainstem becomes continuous with the spinal cord
What route do the 2 roots of the trigeminal nerve take to reach the middle cranial fossa ?
The two roots of the trigeminal nerve continue anteriorly, passing over a ridge of bone (the petrous part of the temporal bone) to enter the middle cranial fossa.
Name the hardest piece of bone in the body
The petrous part of the temporal bone
What happens to the roots of the trigeminal nerve once they enter the middle cranial fossa?
It develops a large swelling called the trigeminal ganglion
In which cranial fossa is the trigeminal ganglion located?
The middle cranial fossa
What does the trigeminal ganglion contain?
It contain the cell bodies of all the sensory nerve fibres in the trigeminal nerve
Describe the cell bodies found inside the trigeminal ganglion
They are much wider than nerve fibres and they take up a lot more space
What is a ganglion?
It is where there are large numbers of nerve cell bodies clustered together in the peripheral nervous system, we find a swelling on the nerve called a ganglion
What do nerve contain thousands of?
Nerve cells
What do nerve cells have?
Processes that arise from the cell body called fibres
Name the divisions of the trigeminal nerve
V1 - the ophthalmic nerve
V2 – the maxillary nerve
V3 – the mandibular nerve
Which nerve cells are found in the trigeminal ganglion?
ONLY sensory nerve cells
What type of nerve is the ophthalmic nerve?
An entirely sensory nerve
What does the ophthalmic nerve supply?
It supplies the:
- Orbit
- Eye
- Much of the skin of the anterior aspects of the upper part of the head
- The upper eyelid
- Parts of the nasal cavity,
- Some of the paranasal air sinuses
- The skin running down the centre of the nose
What type of nerve is the maxillary nerve?
An entirely sensory nerve
What does the maxillary nerve do?
Provides the general sensory supply to the:
- Upper teeth
- Gingivae
- The hard
- Soft palates
- The central part of the skin of the face including the lower eyelid, the sides of the nose and the upper lip.
Where does the maxillary nerve travel after emerging from the trigeminal ganglion?
It travels anteriorly to leave the cranial cavity through the foramen rotundum (round foramen)
Where is the foramen rotundum (round foramen) found?
It is a foramen in the sphenoid bone
After passing the foramen rotundum where does the maxillary nerve go?
It emerges into a space called the pterygopalatine fossa.
Where is the pterygopalatine fossa located?
It is a space that lies adjacent to the palatine bone and the pterygoid plates of the sphenoid bone, just posterior to the maxilla.
What happens at the pterygopalatine fossa?
Some branching of the maxillary nerve occurs
How does the maxillary nerve pass the pterygopalatine fossa?
It passes anteriorly anteriorly through a space called the inferior orbital fissure,
What is the inferior orbital fissure?
a slit which lies between the greater wing of the sphenoid bone (superiorly) and the maxilla (inferiorly
What happens to the maxillary nerve as it passes the inferior orbital fissure?
It changes its name to the infra orbital nerve
Where does the infra orbital nerve travel initially?
In a groove in the maxilla called the infra orbital groove
Then it passes through the infra orbital canal
How is the infra orbital canal formed?
When the infra orbital groove becomes roofed-over more anteriorly it becomes the infra orbital canal
Where does the infra orbital nerve exit the infra orbital canal from?
through the infra-orbital foramen
Where is the infra-orbital foramen located?
Inferior to the inferior orbital margin
What happens to the infra orbital nerve after it passes through the infra orbital foramen?
splits into multiple fine branches to supply the skin of the face
Describe the pathway the maxillary nerve takes stating from the trigeminal ganglion
- foramen rotundum
- pterygopalatine fossa
- Some branching occurs
- Leaves pterygopalatine fossa via inferior orbital fissure
- Changes name to infra orbital nerve
- Infra orbital groove
- Infra orytbial canal
- Exits via infraorbital foramen
- splits into multiple fine branches to supply the skin of the face
Do maxillary nerve fibres synapse in the pterygopalatine ganglion?
No they travel through it
Which nerve synapse in the pterygopalatine ganglion?
facial nerve cells which are on their way to supply structures such as the lacrimal gland in the orbit (produces tears), the nasal glands in the nasal cavity and the accessory salivary glands of the palate.
How do maxillary nerve fibres enter and leave the pterygopalatine ganglion?
They get into the ganglion through one of the ganglionic branches of the maxillary nerve.
They leave the ganglion through branches that emerge directly from it.
Name some branches of the maxillary nerve that emerge from the pterygopalatine ganglion
- Greater palatine nerves
2, lesser palatine nerves - nasal nerves
What do the greater palatine nerves CARRY?
These carry nerve fibres inferiorly onto the hard palate.
How do the greater palatine nerves emerge onto the hard palate?
Through the greater palatine foramen
What do the greater palatine nerves SUPPLY?
provide the sensory supply to the mucosa of the hard palate and the palatine gingivae of the upper teeth
What do the lesser palatine nerves SUPPLY?
the soft palate
Where do the nasal nerve run?
They pass medially into the nasal cavity
Where does the longer nasal nerve go after entering the nasal cavity?
it runs along much of the length of the nasal septum before passing through a canal in the hard palate (the incisive canal) to emerge onto the anterior aspect of the hard palate
What do the nasal nerves supply?
the anterior aspects of the hard palate, including the palatine gingivae of the teeth up to and including those adjacent to the canine
After giving off its ganglionic branches what does the maxillary nerve give of?
the posterior superior alveolar (PSA) nerve
where does the posterior superior alveolar (PSA) nerve travel?
travels inferiorly on the posterior surface of the maxilla, typically dividing as it does so.
How does the posterior superior alveolar nerve enter the maxilla?
Through small foramina
Where does the posterior superior alveolar nerve travel after entering the maxilla?
Under the mucosa of the lateral wall of the maxillary air sinus, dividing further as they go.
What does the dividing of the posterior superior alveolar contribute to?
They contribute to a plexus (network) of nerves located just superior to the teeth – the superior dental plexus
Where is the superior alveolar plexus found?
Just superior to the teeth
What does the superior alveolar plexus supply?
It sends branches to the teeth, providing them with their nerve supply.
What do the parts of the plexus derived from the posterior superior alveolar nerve supply ?
Most parts of the upper molar teeth and the buccal gingivae associated with them
What does the maxillary nerve do after giving off the posterior superior alveolar nerve?
It passes through the inferior-orbital fissure and becomes the infra-orbital nerve.
As well as becoming the inferior orbital nerve what does the laxity nerve give off in a MINORITY of people?
Gives off the middle superior alveolar (MSA) nerve
Where does the middle superior alveolar nerve travel?
Travels inferiorly underneath the mucosa on the lateral wall of the
maxillary air sinus to join the superior dental plexus
What do the parts of the plexus derived from the middle superior alveolar nerve supply ?
Supplies a small part of the first upper molar, the upper premolars and the buccal gingivae associated with the latter.
What does the infra orbital nerve give ogg after the. middle superior alveolar nerve?
The anterior superior alveolar (ASA) nerve.
Where does the anterior superior alveolar nerve travel?
This travels inferiorly underneath the mucosa of the lateral wall of the maxillary air sinus to join the anterior regions of the superior dental plexus.
What does the anterior superior alveolar nerve supply?
supplies the anterior maxillary teeth and the labial gingivae associated with them.
As the middle superior alveolar nerve is only present in a small number of people what is the area it would have supplied instead supplied by?
From the PSA and ASA nerve.
All the superior alveolar nerves have branches that run under where?
the mucosa of the maxillary air sinus
What can inflammation of the maxillary air sinus do?
Inflammation in the sinus (sinusitis) can stimulate the nerves, producing what feels like dental pain even if there’s nothing wrong with the teeth themselves
What is referred dental pain?
When the pain feels like it’s coming from one site when it’s actually being generated somewhere else
Describe the maxillary bone
It is a porous bone m
What is the advantage of the maxillary bone being porous?
makes it amenable to local infiltration of anaesthetic solution near to the site you intend to work on
What type of anaesthetic techniques can we use to anaesthetise the maxilla?
We can use an infiltration or apply a nerve block to the larger branches
Name the 2 nerve blocks we use on the maxilla
- The Infra-Orbital Nerve Block
2. The Posterior Superior Alveolar Nerve Block
Where is anaesthetic solution deposited in an Infra-Orbital Nerve Block?
Deposited in the vicinity of the infra-orbital foramen
Which nerve do we expect to anaesthetised is an Infra-Orbital Nerve Block is administered correctly?
The solution will enter the foramen and anaesthetise the distal part of the INFRA ORBITAL nerve and the branches which emerge from it.
Which facial structures are anaesthetised in an Infra-Orbital Nerve Block?
the upper lip
the teeth to the level of the canine and their labial gingivae
Why is the upper lip anaesthetised when we administer an Infra-Orbital Nerve Block?
because the block affects the terminal branches to the skin of the face)
Why are the teeth to the level of the canine and their labial gingivae anaesthetised when we administer an Infra-Orbital Nerve Block?
Because the anterior superior alveolar nerve is a branch of the infra orbital nerve so will be blocked
What is not anaesthetised when we administer an Infra-Orbital Nerve Block?
The palatine gingivae adjacent to the anaesthetised teeth
Pre-molars and their buccal gingivae (supplied by MSA or PSA)
Where can the solution from an infra orbital nerve block accidentally be deposited?
Into the orbit
What is the effect of local anaesthetic being deposited into the orbit?
Some of the muscles which move the eye will become temporarily paralysed. As a result, movement of the eyes will become uncoordinated and can lead to diplopia
ALSO teeth won’t be anaesthetised
Why can the Posterior Superior Alveolar nerve be anaesthetised ?
As its branches run along the posterior surface of the maxilla
What is anaesthetised when we administer a posterior superior alveolar nerve block?
the molars and their buccal gingivae but
What is not anaesthetised when we administer a posterior superior alveolar Nerve Block?
The palate is unaffected
can’t be relied upon to anaesthetise the pre-molars and their buccal gingivae
What risk is associated with administrating a posterior superior alveolar nerve block?
Possible to introduce infection into the pterygoid venous plexus as it is located in the space posterior to the maxilla
What can happen if the pterygoid venous plexus gets infected?
The infection can travel along the venous communications of the pterygoid plexus into the cranial cavity
What supplies the mucosa of the hard palate?
The greater palatine nerve
What supplies the anterior aspects of the hard palate, including the palatine gingivae of the teeth up to and including those adjacent to the canine?
The nasal nerves
What supplies the palatine gingivae of the upper teeth?
The greater palatine nerve
Give an example of referred dental pain
If the maxillary sinus gets inflamed (sinusitis) it can stimulate the nerves, producing what feels like dental pain even if there’s nothing wrong with the teeth themselves
What supplies the soft palate?
The lesser palatine nerve
