2021 MSC TMJ Mandible and Muscles of Mastication 2013

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2021/7021MSCOral Biology

Semester 1 2013

Laboratory Manual

Anatomy of the Head and Neck Region

Laboratory 2

Temporomandibular Joint,Infratemporal Fossa

Muscles of MasticationMuscles of Facial Expression


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Laboratory 2: Osteology; Temporomandibular joint; Muscles of mastication;

Muscles of facial expression.

Learning objectives.

1. Identify the surface projections of major bony landmarks of the skull on a living subject.2. Locate and identify the temporal and infratemporal fossae and pteryogpalatine fossa

3. Describe the anatomy of the mandible.

4. Describe the anatomy of the temporomandibular joint.

5. Identify the muscles of mastication

6. Describe an overview of the masticatory cycle and specific actions of the key musclesduring the masticatory cycle.

7. Identify the muscles of facial expression and state their actions.

Station 1

Surface anatomyUse a skull model or specimen to locate the following structures.

If working with a partner, seek their permission to palpate the structure, or locate and palpate these

structures on yourself .

external occipital protuberancemastoid process (what is located within this structure?)

zygomatic arch (trace along its length to meet the temporal bone)

What are the two processes that unite to form this arch?

____________________________________________________________________________

greater wing of sphenoid bone

parietal eminences

frontal eminences

glabella

temporomandibular joint

angle of the mandiblehyoid bone (on yourself! squeeze gently, inferiomedial to the angle of the mandible)

spinous process of C3 and C7 Can you palpate the spinous process of C1?

clavicle: The medial one third of this bone is the origin for a large neck muscle that performs the

actions of flexion (when both left and right sides contract at once) and rotation (when one side only

is contracted).

Identify (and palpate) the neck muscle described above:_____________________________

manubrium (inferior to sternal notch) This bone is one of the two origins of a major neck muscle

(which also forms the boundary for the anterior and posterior triangles of the neck).

Which neck muscle originates on the anterior surface of the manubrium?________________


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Identify two other neck muscles that connect the posterior surface of the manubrium to the:

Hyoid bone _________________________Thyroid ________________________________

Note that these muscles are named for where they originate and insert.

Station 2The superior temporal line is formed by the origin of the temporalis muscle attachment and the

forces generated during temporalis muscle contraction during mastication.

Identify the location of the temporal fossa:

Which four cranial bones form the floor of this fossa?

1.______________________________ 2._____________________________

3.______________________________ 4._____________________________

Which muscle occupies most of the temporal fossa?

_________________________________________________________________

The inferior boundary of the temporal fossa is often arbitrarily nominated as the zygomatic arch.

Infratemporal fossa:The region deep to the mandible and inferior to the zygomatic arch is identified as the

infratemporal fossa.

Which bone and structure forms the ANTERIOR wall of the infratemporal fossa?

___________________________________________________________________________

Which bone forms the LATERAL border of the infratemporal fossa?

___________________________________________________________________________

Which feature of the sphenoid bone forms the MEDIAL boundary of the infratemporal fossa?

___________________________________________________________________________

The POSTERIOR boundary is continuous with the styloid process of temporal bone and the carotid

sheath and its contents.

The SUPERIOR boundary is formed by the infratemporal surface of the greater wing of sphenoid

and the infratemporal crest (a bony ridge between the temporal and sphenoid bones).

The infratemporal fossa continues inferiorly, travelling lateral to the pharynx, into the neck.

The infratemporal fossa contains the medial and lateral pterygoid muscles and the tendon of the

temporalis muscle, which contribute to mastication. See pages 35, 102 and 103 of, Head and Neck

Anatomy for Dental Medicine (2010) Eric W. Baker Editor Thieme Medical Publishers Inc NY USA


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Fig 1.5 pg 4, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA

The infratemporal fossa is continuous with the pterygopalatine fossa which provides pathways for a

number of neurovascular structures which you will explore further in later labs. The major structures

are illustrated below and you can review this region at the following website.http://skullanatomy.info/Individ%20Spaces/Ptg_Fossa/PtPFossa.htm

See also pages 100-105 ofHead & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. ThiemeMedical Publishers Inc NY USA

Fig 1.5 pg 4, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA

Locate and label the boundaries of

the temporal fossa and the

infratemporal fossa on this diagram
http://skullanatomy.info/Individ%20Spaces/Ptg_Fossa/PtPFossa.htmhttp://skullanatomy.info/Individ%20Spaces/Ptg_Fossa/PtPFossa.htmhttp://skullanatomy.info/Individ%20Spaces/Ptg_Fossa/PtPFossa.htm


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Station 3

Mandible Review: Locate and these structures on the bones and label the following diagrams

Head

External surface

NeckCondylar process (head & neck)

Body

Ramus

Angle

Coronoid process

Mandibular (sigmoid) notch

Coronoid notch

Mental foramenMental protuberance

Mental tubercle

Alveolar Process

External oblique line (ridge)

Groove for the facial artery

Pterygoid fovea

Internal surface

Lingula

Mandibular foramen

Mylohyoid groove

Temporal crest (internal oblique line)Retromolar fossa

Mylohyoid ridge (what attaches here?)

Submandibular fossa (what sits here?)

Sublingual fossa (what sits here?)

Genial tubercles (mental spines) (attached?)

Digastric fossa (what attaches here?)Angle - attachment of medial pterygoid


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Fig 1.40 pg22, Head& Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USAUse the diagrams above to illustrate the origins and insertions of the major masticatory muscles

you observe in Station 4

Hyoid bone: Locate and identify the following features on the diagrams below:

Body of the hyoid, Lesser cornu, Greater cornu

Try to find the names of all the muscles that insert onto the hyoid bone. (think infrahyoid and

suprahyoid muscles)


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Gently palpate your hyoid bone. Now swallow.

Which direction does the hyoid bone move initially?_______________________________________

Where would you expect to locate the muscles responsible for this movement?

_________________________________________________________________________________

Which direction does the hyoid bone then move? _________________________________________

Where would you expect to locate the muscles responsible for this movement?

_________________________________________________________________________________


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Station 4

Temporomandibular joint

The name of this joint describes the two bones which articulate together to permit opening, closing

and chewing movements.Overview of Temporomandibular joint (TMJ) and its movement.

The TMJ is a diarthrotic joint that is formed by the opposition of two convex structures with a

fibrocartilaginous articular cartilage in between them. The structure of the joint provides two

different types of movement: ginglymus (hinge) and arthrodial or gliding movement (thus

ginglymoarthrodial joint). Fig 2.21 pg37, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme

Medical Publishers Inc NY USA

Identify the bony features that form

the temporomandibular joint (be

specific)

1.____________________________

_____________________________

2.____________________________

_____________________________

Identify the fibrocartilage structure

in the temporomandibular joint

_____________________________

what is it attached to?

What is meant by the upper and lower joint

cavities of the temporomandibular joint?

___________________________________________

____________________________________________

Identify the mandibular and articular fossae.

What is the role of the articular disc in TMJ function?

____________________________________________

____________________________________________

____________________________________________


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Ligaments supporting the Temporomandibular Joint

Fig 2.20 pg37, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA

Note the location and attachment of the sphenomandibular ligament. What is the clinical

significance of this ligament?

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________


Write a brief description of the clinical disorder of the TMJ illustrated above:

First: orientate yourself with

this image.

What view is shown here?

Now, identify three ligaments

that provide support to the

TMJ.

What do you notice about their

names?


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What is meant by the clinical term crepitis when describing the TMJ?

TMJ Dysfunction syndrome:

Identify which of these three diagrams represents

the following stages:

mouth closed

mouth starting to open

mouth wide open.

For each of these stages, indicate two

characteristic features you observed in the

diagram.


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Station 5

Use the following diagrams to help you identify the masticatory muscles on the cadaveric

specimens Fig 2.12 pg32, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc

NY USA

Although the TMJ movements are complex, the three primary movements are:

Rotation occurs around an axis through the head of each mandibular condyle and is demonstrated

during the initial opening of the mouth (first 15 of opening) where the mandible head remains

within the glenoid (mandibular) fossa of the temporal bone (if you call it the glenoid fossa then also

state it is the temporal bone as there is a glenoid fossa on your scapula too!).

As the mouth opens more than 15 of opening, the head of the mandible glides forward with thearticular disk on to the articular tubercle which results in shifting the joint axis forward. The

movement of the articular disk is aided by the lateral pterygoid muscle (superior fibres), whilst the

mandibular head translates anteriorly due to the pull of the inferior part of the same muscle.

Further depression of the mandible (or opening of the mouth) is the result of synergistic actions of

the digastric, geniohyoid and mylohyoid muscles contracting against a fixed hyoid bone. Fixation of

the position of the hyoid bone occurs through infrahyoid muscle action.

Mastication is initiated consciously however the movements, their sequence and rhythm are

controlled by the central nervous system. An individuals masticatory pattern changes over the

lifespan and can adapt to changes of the stomatognathic system.

Overview of Mastication:

Review the mandibular movements from your initial laboratory notes.Closure of the jaw (including biting) is synergistically actioned by two large (paired) muscles which

elevate the jaw.

Identify these two large superficial muscles:Muscle 1: Prime mover for mandibular elevation:

_______________________________________________________________________________

Muscle 2: A fan- shaped muscle that elevates AND retracts mandible

_______________________________________________________________________________


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Another two pairs of smaller muscles contract synergistically to protrude the mandible and promote

lateral or side to side movement for grinding.

Identify these two muscles:Muscle 1: Orientation of this muscles fibres permits it to work synergistically (together) with the

two large muscles above in elevation of the mandible. It forms a masticatory muscle sling with the

Masseter muscle.

__________________________________________________________

Muscle 2: Located more laterally than the muscle above and has a primary role in initiating

depression of the mandible which is continued by the suprahyoid and infrahyoid muscles and

gravity. Contraction of this muscle and its paired muscle on the other side of skull are considered to

guide the TMJ movement. Its superior head also attaches to the articular disk.

__________________________________________________________

If the two muscles identified above contract together, protrusion of the mandible occurs.

It is important to recognise that unilateral contraction by these muscles contribute to lateral excursion

or grinding .

In addition to the four paired muscles above (ie there are two muscles, one on each side of the

skull/mandible), the buccinator muscle compresses the cheek to ensure food remains between the

occlusal surfaces of the teeth.

See pages 30-35 Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme

Medical Publishers Inc NY USA and Chapter 13 pages 208-215 Textbook of Head & Neck Anatomy

4th Edn Hiat JL and Gartner LP Wolters Kluwer Lippincott Williams and Wilkins Philadelphia PA.

Muscles of mastication: Identify the following muscles in the cadaver and the models.

Muscle Origin Insertion Action

Masseter

Temporalis

Medial

pterygoid

Lateral

pterygoid


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What is the embryological origin of these muscles? (see last page of these notes)

Muscle Embryological origin Innervation Action

Masseter

Temporalis

Medial pterygoid

Lateral pterygoid

What do you notice about the innervation?

Identify the suprahyoid muscles. Which of these muscles affects mandibular movement. What is

their action?

Muscle Action

Digastric

Mylohyoid

Geniohyoid

Stylohyoid


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Fig 2.24b pg38, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA

Identify the infrahyoid muscles that also affect mandibular movements.

Muscle Action

Sternohyoid

Sternothyroid

Thyrohyoid

Omohyoid


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Identify the origins and insertions of the muscles on the hemi mandible diagram below.

Fig 2.24b pg38, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA

On the diagram below, identify the origins and insertions for the muscles of MASTICATION only

Fig 2.24a pg38, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA


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Use the diagram below to assist your identification of the superficial facial muscles on the cadaveric

specimens.


By looking at the locations of these muscles and the direction of their fibres, predict what their general action would be when each is

contracted individually (or in combination if paired muscles).


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Now label the muscles of facial expression on the following diagram.


Identify the innervation (motor nerve supply to the muscles of mastication), the muscles of facial expression(eg cranial nerve and division)


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Embryology revisited: This diagram illustrates the why you are exploring embryology.

You can see that the adult structures derived from each arch, share common features (eg

groups of muscles with common functions, all supplied by specific nerves as illustrated here

and blood supply not illustrated here)

https://reader008.{domain}/reader008/html5/0417/5ad5824566262/5ad582513b12d./bbmapasset135415438341.jpgaccessed March 1st, 2013

See also pages 60-61, particularly figure 4.13 which illustrates the four

pharyngeal pouches, their migration to their final position and the

muscles derived from each arch. Table 4.6 on page 61 is also of

assistance.
http://classconnection.s3.amazonaws.com/519/flashcards/2297519/jpg/bbmapasset1354154383941.jpghttp://classconnection.s3.amazonaws.com/519/flashcards/2297519/jpg/bbmapasset1354154383941.jpghttp://classconnection.s3.amazonaws.com/519/flashcards/2297519/jpg/bbmapasset1354154383941.jpghttp://classconnection.s3.amazonaws.com/519/flashcards/2297519/jpg/bbmapasset1354154383941.jpghttp://classconnection.s3.amazonaws.com/519/flashcards/2297519/jpg/bbmapasset1354154383941.jpg


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2021 MSC TMJ Mandible and Muscles of Mastication 2013

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