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MUSCLES OF MASTICATION
Muscles of masticationMastication is a harmonious and skillful activity which requires the presence and co ordination of not only the muscles of mastication but also the supra infrahyoid muscles, and the facial muscles
MUSCLES OF MASTICATION
• INTRODUCTION• GROWTH AND DEVELOPMENT• ANATOMIC DESCRIPTION• INNERVATION AND VASCULAR SUPPLY• PHYSIOLOGY OF MUSCLE ACTION• APPLIED ASPECTS
MUSCLES OF MASTICATION
• INTRODUCTION
A muscle is defined as an organ that by contraction produces movements of an animal; A tissue composed of contractile cells or fibers that effect movements of an organ or part of the body
Originates from skull &attaches to mandible
functions as A group
mastication, deglutition, speech & respiration
•
GROWTH AND DEVELOPMENTEMBRYOLOGY
• First Pharngeal Arch
Deep portion
Superficial portion
ANATOMIC DESCRIPTION OF MUSCLES OF MASTICATIONANATOMIC DESCRIPTION OF MUSCLES OF MASTICATION
MASSETERMASSETER
ORIGINORIGIN
INSERTIONINSERTION
VASCULAR SUPPLYVASCULAR SUPPLY
INNERVATIONINNERVATION
ACTIONSACTIONS
Powerful elevator muscle
Superficial muscle helps in protruding the mandible
Deep portion helps in stabilizing the condyle against the articular eminence when biting in a protruded position.
Unilateral movement helps in lateral movement of the mandible
ACTIONS OF MASSETERACTIONS OF MASSETER
TEMPORALIS
ORIGINORIGIN
FIBRES ORIENTATION FIBRES ORIENTATION
INSERTIONINSERTION
VASCULAR SUPPLYVASCULAR SUPPLY
INNERVATIONINNERVATION
ACTIONACTION
The strongest of the masticatory musclesDivided into three partsWell developed in carnivores and animals requiring a strong bite forceIt elevates the mandible when it contracts.Contraction of the anterior part raises the mandibleContraction of the middle part elevates and retrudes the mandible
ACTIONS OF TEMPORALISACTIONS OF TEMPORALIS
LATERAL PTERYGOIDLATERAL PTERYGOID
ORIGINORIGIN
FIBRES ORIENTATION FIBRES ORIENTATION
INSERTIONINSERTION
VASCULAR SUPPLYVASCULAR SUPPLY
INNERVATIONINNERVATION
ACTIONSACTIONS
LATERAL PTERYGOID Arises: 2 heads
Upper: Infratemporal surface &crest of greater wing of sphenoid
Lower: Lat surface of the lat pterygoid plate
Inserts: Upper : Anterior & medial surface of
articular disc & Lower : pterygoid fovea below the head of
mandible
Lower head
Upper head
Originates at the outer surface of the lateral pterygoid plate and extends backward upward and outward to insert into the neck of the condyle.When there is bilateral contraction the condyles are pulled down the articular eminences and the mandible is protruded.
Unilateral contraction causes a mediotrusive movement of that condyle and lateral movement of the mandible to the other side
. The inferior lateral pterygoid is active during opening in contrast to the superior part.
INFERIOR
HEAD
MEDIAL PTERYGOIDMEDIAL PTERYGOID
ORIGINORIGIN
FIBRES ORIENTATION FIBRES ORIENTATION
INSERTIONINSERTION
VASCULAR SUPPLYVASCULAR SUPPLY
INNERVATIONINNERVATION
ACTIONSACTIONS
MEDIAL PTERYGOIDArises :2 heads
Superficial:Tuberosity of Maxilla & Pyramidal process of palatine bone
Deep: Medial surface of lateral pterygoid plate
Inserts: Medial surface of ramus and angle of the mandible
Deep head
Superficial head
The medial pterygoid muscle
Originates from the pterygoid fossa and extends downwards backwards and outwards to insert in the medial side of the ramus of the mandible forming a sling along with the masseter at the angle of the mandible.
It assists in closing of the jaw and contraction of the muscle also causes protrusion. Unilateral contraction-mediotrusive movement
VASCULAR SUPPLY
TEMPORALISTEMPORALIS
MASSETERMASSETER
LATERAL PTERYGOIDLATERAL PTERYGOID
MEDIAL PTERYGOIDMEDIAL PTERYGOID
ACCESSORY MUSCLES OF MASTICATION
• Suprahyoid Muscles
Digastric Stylohyoid Mylohyoid Geniohyoid
• Digastric
Two bellies
Origin
Insertion
Innervation
Suprahyoid Muscles
Suprahyoid Muscles
• DigastricVascular Supply
Posterior Belly - Posterior Auricular and occipital Arteries
Anterior Belly – Submental branch of Facial Artery
• Stylohyoid
Origin
Insertion
Vascular Supply – branches of Facial, Posterior Auricular and occipital arteries
Innervation – Stylohyoid branch of Facial Nerve
Action – elevates the hyoid bone and draws it backwards, elongating the floor of mouth
• Mylohyoid Floor of the mouth
Origin
Insertion
Vascular Supply – sub lingual branch of Lingual artery
Maxillary Artery
Submental branch of Facial artery
Innervation – Mylohyoid branch of inferior alveolar nerve
• GeniohyoidOrigin
Insertion
Vascular Supply – lingual artery ( sublingual branch)
Innervation – First cervical spinal nerve through the hypoglossal nerve.
INFRAHYOID MUSCLES
• Sternohyoid Origin – posterior surface of medial part of clavicle
upper posterior aspect of the manubrium sterni
Insertion – inferior border of body of hyoid bone
Vascular Supply – superior thyroid artery
Innervation – Ansa cervicalis
Action – depresses hyoid bone
• Omohyoid Two bellies
Origin Inferior belly– upper border of scapula near the scapular notch and superior transverse scapular ligamentsInsertion – intermediate tendonSuperior belly – intermediate tendonInsertion – lower part of body of hyoidVascular Supply – superior thyroid and lingual arteriesInnervation – Ansa cervicalis
• Sternothyroid Origin – posterior surface of manubrium sterni
posterior edge of cartilage of first rib
Insertion – oblique line on the lamina of thyroid cartilage
Vascular Supply – superior thyroid and lingual arteries
Innervations – Ansa cervicalis
• ThyrohyoidOrigin - oblique line on the lamina of thyroid cartilage
Insertion – lower border of greater cornua and body of hyoid bone
Vascular Supply - superior thyroid and lingual arteries
Innervations – First spinal cervical nerve (hypoglossal nerve)
Action – depresses hyoid bone
PHYSIOLOGY OF MUSCLES OF MASTICATIONPHYSIOLOGY OF MUSCLES OF MASTICATION
General Mechanism of Muscle ContractionGeneral Mechanism of Muscle Contraction
MANDIBULAR MOVEMENTS AND MUSCLE ACTIVITY
COMPLEX NEUROMUSCULAR ACTIVITY
ELECTROMYOGRAPHY OF :-
• MANDIBULAR OPENING• -Lat,med
Pterygoid,digastric,mylohyoid & Geniohyoid
-No Activity In Temporalis & Masseter Muscle
• MANDIBULAR CLOSING - With Out Resistance; masseter & Med Pterygoid
- With Resistance Temporalis, masseter, Med Pterygoid
MANDIBULAR MOVEMENTS AND MUSCLE ACTIVITY
• RETRUSION
-Post Fibers Of Temporalis,Deep fibres of Masseter
• PROTRUSION
-Without Occl Contact Lat &Med Pterygoid And Masseter
-With Occl Contact Pterygoids,masseter
MANDIBULAR MOVEMENTS AND MUSCLE ACTIVITY
LATERAL MOVEMENTS
• Ipsilateral Contraction Of The Posterior & Middle Fibers Of Temporalis Ms,Masseter Ms
• Contralateral Contraction Of Lat & Med Pterygoid Ms & Ant Fibers Of TheTemporalis
MUSCLE HYPERTROPHY
• Results from increase no of actin & Myosin filaments• Significant hypertrophy in 6-10 weeks
Causes:• Developmental defects• Functional disturbances• Inflammations & Infections• Metabolic changes• Neoplasm• Over loading the muscle
MUSCLE HYPERTROPHY
• Massetric Hypertrophy
Congenital facial hemi hypertrophy
Functional hypertrophy
TRISMUS
A Motor Disturbance Of The Trigeminal Nerve, Especially Spasm Of The Muscles Of Mastication With Difficulty In Opening The Mouth
Causes :• Trauma To Muscle / Blood Vessels• Hemorrhages• Infections• Excessive Volume Of LA .• Contaminated LA• Trauma• Profound Muscle Spasm, Tenderness & Trismus