2021 msc tmj mandible and muscles of mastication 2013
TRANSCRIPT
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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?
_________________________________________________________________________________
_________________________________________________________________________________
_________________________________________________________________________________
Fig 2.22 pg37, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA
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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Fig 2.16 pg35, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA
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.
Fig 2.1 pg24, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA
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.
Fig 2.2 pg25, Head & Neck Anatomy for Dental Medicine (2010) Eric W. Baker Ed. Thieme Medical Publishers Inc NY USA
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.
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