Lab 5 Nerves

7/27/2019 Lab 5 Nerves

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2021MSC

Oral Biology

Semester 1 2013

Laboratory Manual

Anatomy of the Head and Neck Region

Laboratory 5

Cranial Nerves,

Local Anaesthesia

Oral Cavity

Pharynx and larynx



Laboratory 6: Cranial Nerves, foramina and innervation

Learning Objectives

Station 1Cranial nerves: Osteological foramina

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Review the foramina on the skull through which the cranial nerves pass.

Study the cranial nerves in relation to their course in head and neck and the structures theyinnervate.

Be able to identify the cranial nerves from the brainstem.

Identify the nerves closely related to the pharyngeal muscles.

Describe the primary innervation of structures in the oral cavity.

Describe the innervation of the tongue muscles.

Identify and study the relationship of important nerves in the floor of the mouth.

Study the anatomical relations of the parotid gland. Identify the facial nerve and note the

relationship of the facial nerve with this gland.

Be able to identify the mandibular and maxillary nerves and their main branches; and

describe the structures supplied by these nerves.

Describe the nerve supply of the larynx and the major anatomical features of the larynx.

Be able to identify the nerves of the neck.

Examine the oral cavity and identify the major structural features

Understand the role of the constrictor muscles in swallowing

Explore the muscles of the tongue

On the open skull, identify the foramina through which the cranial nerves pass:

Cribriform plate of the ethmoid bone – Which cranial nerve/nerves?

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Optic canal - Which cranial nerve/nerves?

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Superior orbital fissure - Which cranial nerve/nerves?

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Foramen rotundum - Which cranial nerve/nerves?

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Foramen ovale - Which cranial nerve/nerves?

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Internal acoustic (auditory) meatus - Which cranial nerve/nerves?

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Jugular foramen - Which cranial nerve/nerves?

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Hypoglossal canal - Which cranial nerve/nerves?

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Identify and label the foramina through which each of the cranial nerves exits (later, you

can also label the other structures to help your review). Indicate where the nerve will then

progress to (ie what does it innervate)



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Using models and specimen, examine the base of the brain to identify the sites of

emergence of cranial nerves. Name the cranial nerves.

Note how the cranial nerves are numbered sequentially, from anterior to posterior

Note that olfactory and optic nerves appears like extensions of the brain.

Identify the following:

CN 1 – Olfactory bulb & olfactory tract

CN 2 – Optic nerve. Note the optic chiasma

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CN 3 – Oculomotor. Emerge at the junction between pons and midbrain between the

two cerebral peduncles (interpeduncular fossa)

CN 4 – Trochlear. It is the only cranial nerve that emerges from the posterior aspect

of the brain.

CN 5 – Trigeminal. It emerges from the anterior aspect of the pons as two roots

(motor and sensory). The 3 branches of the trigeminal nerve:Ophthalmic (CN 5I or V1) – sensory

Maxillary (CN 5II or V2) – sensory

Mandibular (CN 5III or V3) – sensory & motor

CN 6 – Abducens, CN 7 – Facial & CN 8 – Vestibulocochlear. They emerge at the

angle formed by the medulla, pons and cerebellum. This is a relatively common site

for tumours.

CN 9 – Glossopharyngeal, CN 10 – Vagus and CN 11 – Accessory. They emerge

between the olive and the inferior cerebellar peduncle.

CN 12 – Hypoglossal. It emerges between the olive and pyramid of the medulla.

Now match the cranial nerves to the foramina through which they pass

Cribriform plate of the ethmoid bone

Optic canal

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Foramen Cranial Nerves



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Superior orbital fissure

Foramen rotundum

Foramen ovale

Internal acoustic (auditory) meatus

Jugular foramenHypoglossal canal

By examining the point of emergence from the brain and the point of exit from the skull you

can develop and understanding of the intracranial course of the cranial nerves. The diagram

on the next page illustrates each of the nerves as they pass into the skull (left side) and pass

out of the skull (right side).

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Station 2

Infratemporal fossa:

contains the two pterygoid muscles, branches of the maxillary artery/veins, pterygoid venous

plexus, branches of the mandibular nerve and the chorda tympani.

Boundaries:

Medial: Lateral pterygoid plate

Lateral: Medial surface of the ramus of the mandible

Anterior: Tuberosity of the maxilla

Posterior: Deep part of the parotid region

Superior: greater wing of sphenoid bone

Inferior: Medial pterygoid muscle

Pterygopalatine fossa and pterygomaxillary fissure

Identify the pterygomaxillary fissure and fossa on the TMJ diagram below

Locate the pterygopalatine fossa.

Which branch of the trigeminal nerve can be seen within this fossa?

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Identify the nerves on the above diagram. Identify the trigeminal nerve branches within this fossa

and the areas that they innervate.

Does the diagram above represent sensory or motor innervation?



• Now locate the foramen ovale.

Which branch of the trigeminal nerve can be seen emerging from this foramen?

Identify the major branches of this branch of trigeminal nerve emerging from thisforamen and name the areas they innervate:

Sensory –

Motor –

CLINICAL NOTE:

The inferior alveolar nerve is anaesthetized during dental procedures. Local anesthetic is injected

near the mandibular foramen (through which ligament?) to block the inferior alveolar nerve. This

will usually result in anesthesia of the lower jaw teeth (inferior alveolar nerve) and lower lip

(mental nerve).

Note the superficial part of the parotid gland lying superficial to the masseter muscle. The gland f ills

the gap between the mandible and the mastoid process.

View the lateral side of the face and recognise the relationship/locations of the branches of the facial

nerve, external jugular vein, external carotid artery, parotid duct, superficial temporal vessels,

transverse facial vessels and auriculotemporal nerve to the parotid gland.

The diagram on the next page has had the parotid gland removed to better illustrate the relationships

between the neurovascular and glandular structures in the region.

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Parotid gland



• Now locate the stylomastoid foramen.

Which nerve emerges from this foramen?

This nerve provides special visceral efferent or motor nerve function to all of the

muscles from pharyngeal arch number______? These muscles include those of facial

expression, buccinators, platysma, scalp, external ear, stapedius, stylohyoid and the

______________belly of digestive.

It provides special sensory for taste to which part of the tongue?

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What is the name of the nerve which provides this special sensory taste sensation

(and parasympathetic innervation to the submandibular gland?)

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This nerve has five major branches to the face (plus the nerves to stylohyoid,

digastric and tongue. To represent this, put you right hand palmar surface onto the lateral

side of your face. Your little finger should be on the anterior neck (cervical branches),

your ring finger, marginal mandibular, your middle finger buccal branches, index finger

zygomatic branches and your thumb, temporal branches. There is also a posterior

auricular branch posterior to ear.

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• Where is the petrotympanic fissure?

Name the nerve that emerges from this fissure?

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What structure does it innervate?

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Which cranial nerve carries the preganglionic parasympathetic fibres to the parotid gland?

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Name the ganglion in which these fibres synapse.

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How do the postganglionic secretomotor fibres reach the parotid gland?

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Parasympathetic nerve supply:



If the or near the geniculate ganglion, identify whether

the following clinical signs would be observed:

Motor paralysis of upper and lower parts of the face on the ipsilateral side

Motor paralysis the upper parts of the face on the ipsilateral side

Loss of taste on posterior third of tongueLoss of taste on anterior two thirds of tongue

Altered secretion of lacrimal and salivary glands

Altered secretion of lacrimal, salivary and parotid glands

If the , between the geniculate ganglion and the origin

of chorda tympani, identify how the clinical symptoms may vary:

If the , identify how the

clinical symptoms may vary:

Given that facial nerve damage affects the muscles of facial expression, what specific clinical signs

of impaired facial muscle function would you readily observe?

What specific tests would you use to detect these functional changes?

What is Bell’s Palsy? What clinical signs would you observe or would your patient report?

facial nerve was damaged near its origin

of only

facial nerve was damaged more centrally

facial nerve was damaged as it appears from the stylomastoid foramen



Station 3

Pharynx

Superior pharyngeal

constrictor

Middle pharyngeal

constrictor

Inferior pharyngeal

constrictor

Superior constrictor

Middle constrictor

Inferior constrictor

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Identify the actions of the pharyngeal muscles

Name innervation Action (simple action)

Levator veli palatini Pharyngeal p lexus Elevates palate (name predicts action)

Tensor veli palatini V2 Tenses palate (name predicts action)

Musculus uvulae Pharyngeal p lexus Moves uvula

Palatoglossus P haryngea l p lexus (name p red ic ts ac tion)

Palatopharyngeus Pharyngeal p lexus (name predicts action)

Stylopharyngeus IX (name predicts action)

Salpingopharyngeus

auditory tube

Pharyngeal plexus

origin: medial pterygoid

plate,&

pterygomandibular raphe

Pharyngeal plexus

hyoid bone &stylohyoid

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Pharyngeal plexus

cricoid and thyroid

cartilages

Pharyngeal plexus& recurrent

laryngeal of X

Identify the 3 circular muscles that form the majority of the pharynx on the specimens and models:

Identify the following in the models/specimens provided.

Pharyngeal fascia

pterygomandibular raphe + hamulus + mandible

hyoid bone - stylohyoid ligament (lesser horn) + greater horn

thyroid + cricoid cartilages

oPosteriorly all 3 are attached to pharyngeal raphe



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Superior constrictor

Middle constrictor

Inferior constrictor

Pterygomandibular raphe

Buccinator

3 longitudinal muscles attached to the styloid process, cartilage of the auditory tube

and to the soft palate.

Describe the nerve supply to the muscles of the pharynx.

There are gaps that separate the superior and middle constrictors and the middle and inferior

constrictors. These spaces or gaps are the most common path for nerves and blood vessels to

pass through to the oral cavity and the floor of the mouth.

CN 9 or _______________________passes between the superior and middle

constrictor

Internal laryngeal branch of the vagus nerve (CN 10) (piercing above thyroid

cartilage)

Recurrent laryngeal branch of vagus nerve (CN 10) passing under the inferior constrictor.

What structures do CN9 and CN 10 innervate?

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Larynx

Identify the following cartilages which form the skeleton of the larynx.

Thyroid

Cricoid

Arytenoids

Epiglottis

Identify the following structures inside the larynx:

Glottis

False vocal cord

True vocal cord

Which cranial nerves are involved in speech?

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Describe how the vagus nerve innervates the larynx.

Briefly note the actions on the vocal folds and give their nerve supply.

Note that the larynx is attached to the hyoid bone. Therefore the muscles that elevate the

hyoid bone, elevate the larynx during swallowing. What are the muscles that elevate the

hyoid bone?

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Station 4

Innervation of the teeth and palate

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Revise the structures of the oral cavity

Observe the following structures in the oral cavity.

Teeth

Hard palate

Soft palate

Palatoglossal arch

Palatopharyngeal arch

Tonsil

Uvula (note the symmetrical movement of uvula)

Dorsum of the tongue (note the circumvallate papillae)

Gingiva

Underside of the tongue:

Note the frenulum

Region of the sublingual gland

The opening of the submandibular duct at the sublingual papilla. Note that

the openings of the sublingual gland are often numerous, and may open into

the submandibular duct as well as along the sublingual fold.

Roll your finger on the parotid duct on the face (determine where it lies in

relation to the zygomatic arch) with your teeth clenched, then feel the saliva

emptying into the cheek near the upper second molar teeth as you compresson the duct.

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Soft Palate: This muscular structure is suspended between the nasal pharynx and the oral

pharynx and its f lexibility and soft construction permits muscle act ion to elevate it to isolate

the oral cavity from the nasal pharynx. The sides are connected to the lateral pharyngeal

walls and the anterior to the hard palate. The posterior structure, the uvula is very flexible.

Name the muscles that form the soft palate and give the sensory and motor nerve supply to

this (note there is more than one motor nerve supply to these muscles)

Examine in your colleague the following:

Palatoglossal arch (formed by palatoglossus muscle)

Palataopharyngeal arch (formed by palatopharyngeus muscle)

Palatine tonsils (lie between the 2 arches)

Which nerves typically innervate the upper teeth (note the possible variations):

If you have a challenge anaesthetizing the upper teeth, which additional nerve /s do you need to

anaesthetize.

If you need to anaesthetize the lower teeth, which nerve/s typically innervate the lower teeth?

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Label the features of the hard palate on the figure below

Which nerves typically innervate the hard palate.

List the intrinsic and extrinsic muscles of the tongue.

Understand the nerve supply to the tongue (appreciate the anterior 2/3 and posterior 1/3

supply is different, due to its embryological development):

Sensory -

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Station 5

Floor of the mouth and tongue

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Taste –

Motor -

How do the taste fibres from CN 7 reach the anterior 2/3 of the tongue?

Annotate the diagram below to describe the boundaries of general sensory and tasteinnervation of the tongue, including the specific nerves that innervate the regions

Hyoglossus:

Study the diagrams or specimens which show the relationships of this muscle to the

submandibular gland/duct, lingual and hypoglossal nerves and lingual artery.

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State the path taken by the parasympathetic (secretomotor) fibres to reach the

submandibular/sublingual and parotid glands (clearly identify which cranial nerve these

fibres “hitch” on to.

Revisit the boundaries of the anterior and posterior triangles of the neck.

Note the contents of the posterior triangle. Identify the landmark features.

external jugular vein

spinal accessory nerve (CN 11)

What does CN11 innervate?

Station 6

Neck

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Lab 5 Nerves