The Trigeminal Nerve

Question 1

How many cranial nerves do we have?

Answer 1

12

Question 2

Where do cranial nerves emerge from and what are the 2 exceptions to this?

Answer 2

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

Question 3

Which cranial nerve is the only one to leave the head and neck region?

Answer 3

Cranial nerve X: The vagus nerve

Question 4

What is the fifth cranial nerve called?

Answer 4

The trigeminal nerve

Question 5

What type of fibres does the cranial nerve carry?

Answer 5

It carries both motor and sensory fibres

Question 6

What does the trigeminal nerve supply?

Answer 6

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.

Question 7

Which area of the mouth is not supplied by the trigeminal nerve?

Answer 7

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)

Question 8

Where does cranial nerve V originate from?

Answer 8

The brainstem

Emerges from the lateral aspect of the pons

Question 9

How many nerve roots does the trigeminal nerve emerge in?

Answer 9

It emerges as two separate nerve roots:

These are called the sensory and the motor roots of the trigeminal nerve.

Question 10

Which of the 2 roots of the trigeminal nerve is bigger?

Answer 10

The sensory root is much bigger than the motor root

Question 11

Where do the 2 roots of the trigeminal nerve run after emerging from the brain stem?

Answer 11

The two roots run together, passing anteriorly through the posterior cranial fossa.

Question 12

Where do the 2 roots continue to after passing the posterior cranial fossa?

Answer 12

1. 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.

Question 13

What is the hardest piece of bone in the body called?

Answer 13

the petrous part of the temporal bone

Question 14

What happens to the trigeminal nerve once it enters the middle cranial fossa?

Answer 14

Almost immediately after entering the middle cranial fossa, the sensory root develops a large swelling. This is the trigeminal ganglion

Question 15

What is the trigeminal ganglion?

Answer 15

A large swelling develops in the sensory root

Question 16

What does the trigeminal ganglion contain?

Answer 16

The cell bodies of all the sensory nerve fibres in the trigeminal nerve

Question 17

Why do cell bodies take up a lot of space?

Answer 17

Because cell bodies are wider than nerve fibres

Question 18

What is a ganglion?

Answer 18

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

Question 19

What do nerves contain?

Answer 19

Thousands of nerve cells which have cell bodies and has cell processes called fibres

Question 20

What do General sensory nerve cells in the trigeminal nerve look like?

Answer 20

They look like they have a single process coming from the cell body

Question 21

What type of cells does the trigeminal ganglion not contain?

Answer 21

Does not contain motor nerve cells

These are still travelling alongside in the motor root.

Question 22

How many divisions does the trigeminal ganglion split into?

Answer 22

3 Divisions:
V1 - the ophthalmic nerve
V2 – the maxillary nerve
V3 – the mandibular nerve

Question 23

What type of fibres are found in V1- the ophthalmic nerve?

Answer 23

all V1 fibres are sensory

Question 24

What does the ophthalmic nerve supply?

Answer 24

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.

Question 25

What doesn’t the ophthalmic nerve carry?

Answer 25

doesn’t carry visual information

Question 26

What type of fibres are found in V2 – the maxillary nerve

Answer 26

The maxillary nerve is entirely sensory

Question 27

What does the maxillary nerve supply?

Answer 27

Provides the general sensory supply to the:

1. Upper teeth
2. Gingivae
3. The hard and soft palates
4. The central part of the skin of the face including the lower eyelid
5. The sides of the nose and the upper lip.

Question 28

Where does V2 travel once emerging from the trigeminal ganglion?

Answer 28

V2 travels anteriorly to leave the cranial cavity through the foramen rotundum (round foramen)

Question 29

Where is the foramen rotundum found?

Answer 29

In the sphenoid bone

Question 30

Where does the V2 go after leaving the cranial cavity?

Answer 30

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)

Question 31

What happens to the maxillary nerve once it leaves the pterygopalatine fossa?

Answer 31

Passes anteriorly through a space called the inferior orbital fissure,
On doing so, it changes its name to the infra-orbital nerve

Question 32

Where is the inferior orbital fissure?

Answer 32

It is a slit which lies between the greater wing of the sphenoid bone (superiorly) and the maxilla (inferiorly)

Question 33

When does V2 change its name and what to?

Answer 33

When it passes through the inferior orbital fissure

Changes to the infra-orbital nerve

Question 34

Where does the infra-orbital nerve travel to?

Answer 34

1. The infra-orbital nerve travels initially in a groove in the maxilla called the infra-orbital groove
2. The travels into the infra-orbital canal.
3. The infra orbital nerve then emerges from this canal immediately inferior to the inferior orbital margin through the infra-orbital foramen.
4. It then splits into multiple fine branches to supply the skin of the face as mentioned above

Question 35

Why is cranial nerve x called and why is it special?

Answer 35

The vagus nerve

This is the only nerve to leave the head and neck region