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