lecture 2 Flashcards
What is special about the mandibular division of the trigemnal nerve?
It contains both sensory and motor nerve fibres.
Where does the sensory component of the mandibular division arise from?
From the inferior aspect of the trigeminal ganglion
Where does the inferior aspect of the trigeminal ganglion exit the cranial cavity from?
Exits the cranial cavity almost immediately through foramen ovale
What does the inferior aspect of the trigeminal ganglion give rise to?
The sensory component of the mandibular division
When do the sensory and motor components fuse together?
Immediately after emerging from the foramen into the infratemporal fossa.
What does the infratemporal fossa contain?
- Several of the muscles of mastication
- The maxillary artery and its branches
- The pterygoid plexus of veins
- The mandibular nerve
What is the pterygoid plexus of veins a route for?
It is a route for transmitting infection into the cranial
cavity
What happens if an infection spreads into the infra temporal fossa?
The infection can spread to other sites through the fossa’s communication with several spaces in your head.
The spread of infections between the ‘spaces’ of the head can lead to serious, even fatal conditions.
Where can infections of the infratemporal fossa originate?
Such infections can originate in the dental tissues or be introduced during dental procedures.
What does the infratemporal fossa communicate with medially?
Communicates medially with the pterygopalatine fossa
Where is the pterygopalatine fossa located?
positioned posterior to the maxilla
What forms the lateral boundary of the infratemporal fossa?
the ramus of the mandible
What is the infratemporal fossa continuous with superiorly?
Superiorly, it is continuous with the temporal fossa at the level of the zygomatic arch
Name one of the initial branches of the mandibular nerve
The nerve to medial pterygoid
What does the nerve to medial pterygoid supply?
Supplies the medial pterygoid muscl
What happens to the maxillary nerve after it has given off the nerve to medial pterygoid and another small nerve?
he mandibular nerve splits into two parts:
- Anterior trunk
- Posterior trunk
Describe the nerve fibres found in the anterior trunk
It is mainly motor with one sensory branch
Describe the nerve fibres found in the posterior trunk
It is mainly sensory with one motor branch
Which trunk is smaller the posterior or anterior trunk?
The anterior trunk
What does the anterior trunk supply?
Supplies the:
temporalis
lateral pterygoid
masseter muscles
What is the sensory branch of the anterior trunk called?
The long buccal nerve
Where does the long buccal nerve run?
It travels anterolaterally, passing anterior to the ramus of the mandible.
What does the ling buccal nerve supply?
the buccal gingivae adjacent to the mandibular molars
When must the ling buccal nerve be anaesthetised?
When mandibular molars need to be extracted
What does a long buccal block anaesthetise?
anaesthetises the long buccal nerve as it passes anterior to the mandibular ramus.
How many branches does the posterior trunk have?
It has three large branches
They are mainly sensory
Name the 3 branches of the posterior trunk
- The Auriculotemporal Nerve
- The Lingual Nerve
- The Inferior Alveolar Nerve
Describe the nerve fibres in the Auriculotemporal Nerve?
It is entirely sensory
What is unusual about the configuration of the first part of the Auriculotemporal Nerve?
It splits into two branches that run on either side of the middle meningeal artery
When do the 2 branches of the first part of the Auriculotemporal Nerve reunite?
on the other side of the middle meningeal artery
What is the middle meningeal artery?
A branch of the maxillary artery
What happens if the middle meningeal artery ruptures?
Can lead to an extradural haemorrhage inside the cranial fossa
Where does the auriculotemporal nerve travel?
Travels through the upper regions of the infratemporal fossa before passing posterior to the temporomandibular joint and turning superiorly to run just anterior to the auricle of the ear
What does the auriculotemporal nerve supply?
The temporomandibular joint
The temporal region
Where does the lingual nerve travel?
- Runs inferiorly through the infratemporal fossa deep to the lateral pterygoid,
- it then runs anteroinferiorly between the medial pterygoid muscle and the ramus of the mandible
- Then it continues to run anteriorly immediately passing media to the root of the 3rd molar
What is the danger with the lingual nerve being in close proximity to the 3rd molar?
It is vulnerable to damage when this tooth is being extracted.
What happens to the lingual nerve as it passes the 3rd molar?
It divides into numerous small branches
What does the lingual nerve supply?
Sensory innervation to the:
1. lingual gingivae,
2. The mucosa covering the floor of the mouth
3, The anterior 2/3 of the tongue.
Where does the inferior alveolar nerve travel?
- It runs through the infratemporal fossa just posterior to the lingual nerve
- It passes deep to the lateral pterygoid muscle before running between the medial pterygoid muscle and the ramus of the mandible.
Describe the proximal (Initial) region of the inferior alveolar nerve
This region contains both motor and sensory fibres
What do the motor fibres of the inferior alveolar nerve supply?
The anterior belly of the digastric muscle
The mylohyoid muscle
Name the branch of the alveolar nerve that supplies the mylohyoid?
nerve to mylohyoid.
What happens to the inferior alveolar nerve once it branches into the nerve to mylohyoid?
The nerve enters the ramus of the mandible through the mandibular foramen on the medial surface of the mandibular ramus.
It then runs anteriorly through the mandibular body, supplying the teeth as it goes, before reaching the mental foramen.
What happens to the inferior alveolar nerve at the mental foramen?
Part of the nerve emerges into the soft tissues over the anterior aspect of the mandible
This is the mental nerve
What does the mental nerve supply?
It supplies:
the skin and mucosa of the lower lip
The skin over the chin
The labial gingivae of the anterior mandibular teeth.
What happens to the inferior alveolar nerve once it gives off the mental nerve?
The inferior alveolar nerve changes its name to the incisive nerve
Where does the incisive nerve travel?
It continues anteriorly inside the mandible
What does the incisive nerve supply?
The anterior mandibular teeth and their periodontal ligament
Where do the central incisor receive its innervation from?
the central incisor can receive dual innervation from the left and right incisive nerves
What type of anaesthetic do we usually give to anaesthetise the mandibular nerve?
A nerve block
Why are we more likely to give a nerve block to anaesthetise the mandibular nerve?
Because the cortical bone of the mandible is denser than that of the maxilla which means it presents more of a barrier to infiltrating anaesthetic solution than is the case in the upper jaw.
What does the inferior alveolar nerve block aim to anaesthetise?
The inferior alveolar nerve just proximal to the point where it enters the mandibular foramen.
What is the inferior alveolar nerve block sometimes called?
Inferior dental nerve block
What should an inferior alveolar nerve block anaesthetise?
- All the ipsilateral mandibular teeth (IA nerve
and incisive branch). - The lingual gingivae of these teeth (Lingual nerve)
- The buccal and labial gingivae of the premolars, canine and incisors (IA nerve
and mental branch).
What is the buccal gingivae of the molars supplied by?
The long buccal nerve
Will the buccal gingivae of the molars be anaesthetised by an inferior alveolar nerve block?
NO because it is supplied by the long buccal nerve
Why can the mandibular central incisors still have sensation after an inferior alveolar nerve block?
As they can receive fibres from both incisive nerves so the tooth could retain sensation even when the ipsilateral inferior alveolar nerve block has been successful.
What does the parotid gland wrap around?
The parotid gland wraps around the posterior border of the mandibular ramus
What can happen if the inferior alveolar nerve block is administrated incorrectly>
You could anaesthetise the facial nerve branches in the gland, thereby causing temporary unilateral facial paralysis
What does the inferior alveolar nerve lie immediately superficial to?
The medial pterygoid muscle
What muscle can you damage when administrating an inferior alveolar nerve block and what can the consequence be?
Can damage the medial pterygoid muscle
can cause prolonged discomfort for the patient.
How can the distal part of the inferior alveolar nerve be blocked?
By using a mental nerve block
OR
an incisive nerve block
What nerve does a using a mental nerve block anaesthetise?
The mental nerve
What nerve does a using a an incisive nerve block anaesthetise?
The mental and incisive nerves
Where does the mental foramen usually lie?
Between the apices of the mandibular premolars.
What can happen if you administer an increased volume of local anaesthetic to the mental foramen?
It will encourage the solution into the mandible through the mental foramen where it can anaesthetise the incisive nerve.
How can we encourage the solution into the mandible through the mental foramen when we administer a mental nerve block
By Administering an increased volume of anaesthetic solution and applying pressure to the soft tissues in the vicinity of the mental foramen during the injection
Through which foramen does the inferior alveolar nerve enter the mandible through?
The mandibular foramen
What happens to the inferior alveolar nerve before it enters the mandibular foramen?
it gives off the nerve to mylohyoid
Where does the sphenomandibular ligament run?
runs from the base of the skull to the lingula, a tongue- shaped projection of bone lying next to the mandibular foramen
What can the sphenomandibular ligament interfere with?
An inferior alveolar nerve block procedure
Does the lingual nerve enter the mandible?
NO
It runs anteriorly medial to the mandibular ramus and body
What does the lingual nerve run really close to?
It runs immediately medial to the roots of the third molar so it is vulnerable to damage here during extraction of this tooth.
Initially what does the long buccal nerve run medially to?
The ramus of the mandible
Where does the long buccal nerve run after running medially to the rams the mandible?
It crosses anterior to the ramus to reach the soft tissues of the buccal region
What 2 features can be used when applying an inferior alveolar block?
- The external oblique ridge
2. The coronoid notch
Which landmarks do we use to try and find the mental foramen?
Usually lies between the apices of the 1st and 2nd premolar roots.
