The Trigeminal Nerve Flashcards
How many cranial nerves do we have?
12
Where do cranial nerves emerge from and what are the 2 exceptions to this?
Cranial nerves are peripheral nerves that emerge from the brainstem before travelling through the fissures and foramina of the skull in order to reach their target organs.
With the exception of cranial nerves I and II
Which cranial nerve is the only one to leave the head and neck region?
Cranial nerve X: The vagus nerve
What is the fifth cranial nerve called?
The trigeminal nerve
What type of fibres does the cranial nerve carry?
It carries both motor and sensory fibres
What does the trigeminal nerve supply?
Provides the general sensory nerve supply to almost all of the structures of the mouth
Supplies 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.
Which area of the mouth is not supplied by the trigeminal nerve?
Some structures in the posterior aspect of the oral cavity, including the posterior part of the tongue
They receive general sensory supply from the glossopharyngeal nerve (cranial nerve number IX)
Where does cranial nerve V originate from?
The brainstem
Emerges from the lateral aspect of the pons
How many nerve roots does the trigeminal nerve emerge in?
It emerges as two separate nerve roots:
These are called the sensory and the motor roots of the trigeminal nerve.
Which of the 2 roots of the trigeminal nerve is bigger?
The sensory root is much bigger than the motor root
Where do the 2 roots of the trigeminal nerve run after emerging from the brain stem?
The two roots run together, passing anteriorly through the posterior cranial fossa.
Where do the 2 roots continue to after passing the posterior cranial fossa?
- The two roots of the trigeminal nerve continue anteriorly
2. They pass over a ridge of bone (the petrous part of the temporal bone) to enter the middle cranial fossa.
What is the hardest piece of bone in the body called?
the petrous part of the temporal bone
What happens to the trigeminal nerve once it enters the middle cranial fossa?
Almost immediately after entering the middle cranial fossa, the sensory root develops a large swelling. This is the trigeminal ganglion
What is the trigeminal ganglion?
A large swelling develops in the sensory root
What does the trigeminal ganglion contain?
The cell bodies of all the sensory nerve fibres in the trigeminal nerve
Why do cell bodies take up a lot of space?
Because cell bodies are wider than nerve fibres
What is a ganglion?
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 nerves contain?
Thousands of nerve cells which have cell bodies and has cell processes called fibres
What do General sensory nerve cells in the trigeminal nerve look like?
They look like they have a single process coming from the cell body
What type of cells does the trigeminal ganglion not contain?
Does not contain motor nerve cells
These are still travelling alongside in the motor root.
How many divisions does the trigeminal ganglion split into?
3 Divisions:
V1 - the ophthalmic nerve
V2 – the maxillary nerve
V3 – the mandibular nerve
What type of fibres are found in V1- the ophthalmic nerve?
all V1 fibres are sensory
What does the ophthalmic nerve supply?
The orbit and eye and much of the skin on the anterior aspects of the upper part of the head
It also supplies parts of the nasal cavity, some of the paranasal air sinuses and the skin running down the centre of the nose.
What doesn’t the ophthalmic nerve carry?
doesn’t carry visual information
What type of fibres are found in V2 – the maxillary nerve
The maxillary nerve is entirely sensory
What does the maxillary nerve supply?
Provides the general sensory supply to the:
- Upper teeth
- Gingivae
- The hard and 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 V2 travel once emerging from the trigeminal ganglion?
V2 travels anteriorly to leave the cranial cavity through the foramen rotundum (round foramen)
Where is the foramen rotundum found?
In the sphenoid bone
Where does the V2 go after leaving the cranial cavity?
It emerges into a space that lies adjacent to the palatine bone and the pterygoid plates of the sphenoid bone, just posterior to the maxilla (pterygopalatine fossa)
What happens to the maxillary nerve once it leaves the pterygopalatine fossa?
Passes anteriorly through a space called the inferior orbital fissure,
On doing so, it changes its name to the infra-orbital nerve
Where is the inferior orbital fissure?
It is a slit which lies between the greater wing of the sphenoid bone (superiorly) and the maxilla (inferiorly)
When does V2 change its name and what to?
When it passes through the inferior orbital fissure
Changes to the infra-orbital nerve
Where does the infra-orbital nerve travel to?
- The infra-orbital nerve travels initially in a groove in the maxilla called the infra-orbital groove
- The travels into the infra-orbital canal.
- The infra orbital nerve then emerges from this canal immediately inferior to the inferior orbital margin through the infra-orbital foramen.
- It then splits into multiple fine branches to supply the skin of the face as mentioned above
Why is cranial nerve x called and why is it special?
The vagus nerve
This is the only nerve to leave the head and neck region
