MUSCLES OF MASTICATION : MUSCLES OF MASTICATION Definition of muscle : Definition of muscle Muscle can be defined as an organ or tissue that by contraction produces movement of an animal.
A tissue composed of contractile cells or fibers that affect the movement of an organ or part of the body Classification of muscles : Classification of muscles Basis of classification-
1 Depending upon striations.
a) striated b)non-striated
2 Depending upon control.
a) voluntary b)involuntary muscles.
3 Depending upon the function.
a) skeletal muscle b)cardiac muscle c)smooth muscle. Slide 4: Units of skeletal muscle are the muscle fibers, each of which act as a single cell having hundreds of nuclei (syncytial striated myocytes).
Fibers are arranged in bundles of various sizes and pattern called fasciculi.
Connective tissue fills the spaces between muscle fibres within a fasciculus where it is known as the endomyscium. SKELETAL MUSCLE Slide 5: Each fasciculus is also surrounded by a strong connective tissue sheath or perimysciun.
Surrounding the whole muscle lies epimyscium.
Cell membrane of muscle fibre is known as sarcolemma while their cytoplasm is called sarcoplasm.
Sarcoplasm is divided into longitudinal threads or myofibrils each of 1 µm in diameter.
Each muscle fiber consists of several hundred to several thousand myofibrils Muscles of mastication : Muscles of mastication Primary muscles
Secondary or accessory muscles
Buccinator Slide 8: There are four pairs of muscles attached to mandible, primarily responsible for
Lateral movement Slide 9: They are functionally classified as:
Upper head of lateral pterygoid
Lower head of lateral pterygoid
Mylohyoid DEVELOPMENT OF MUSCLES OF MASTICATION : DEVELOPMENT OF MUSCLES OF MASTICATION The muscular system develops from intra embryonic mesoderm
Muscle tissues develop from embryonic cells called myoblast.
Muscular component of Branchial arch form many striated muscles in the head and neck region.
Muscles of mastication are derived from first brachial arch that is the MANDIBULAR ARCH. Slide 11: Lateral View Of A Four Week Embryo Showing Muscles Derived From Branchial Arches Slide 12: MASSETER Slide 14: TEMPORALIS Slide 16: MEDIAL PTERYGOID Slide 18: LATERAL PTERYGOID THE ACCESSORY MUSCLES OF MASTICATION : THE ACCESSORY MUSCLES OF MASTICATION DIGASTRIC
BUCCINATOR Slide 23: DIGASTRIC Slide 25: GENIOHYOID Slide 27: MYLOHYOID Slide 29: BUCCINATOR Clinical examination : Clinical examination Masseter: Fingers are placed over the patients Zygomatic arch,Angle of mandible and body to feel the muscle. Slide 32: Temporalis:
Fingers are placed over the patients temples to feel the muscle. Slide 33: Medial pterygoid:
Index finger is used to touch the medial pterygoid muscle on the inner surface of the ramus. Slide 34: Lateral pterygoid:
The little finger is inserted facial to the maxillary teeth and around distal to the pterygomaxillary, [or] hamular notch, to palpate the muscle. APPLIED ANATOMY : APPLIED ANATOMY APPLIED ASPECTS : APPLIED ASPECTS Slide 43: Myofascial PainWhen the nerve that is connected to the muscle becomes irritated small nodules or contractures form causing the muscle to become tight and painful. These contractures are called trigger points. Trigger points will often refer pain into distant locations. For example it is very common for jaw muscles with myofascial pain to refer pain into the teeth or ears. Slide 44: In addition to pain, muscles with myofacial pain also fatigue more easily and have decreased strength and range of motion. Headaches in the temples are usually the result of myofacial pain within the temporalis muscle, which is a jaw closing muscle. This can occur when the jaw muscles are chronically strained such as in teeth clenching or poor posture, through an acute trauma, or with nerve injury or jaw joint dysfunction. Slide 45: Temporal TendonitisThis can occur when there is chronic strain from the temporalis muscle pulling on the tendon that attaches to the mandible. This can cause sharp headaches in the temples, just to the sides of the eyes. Slide 46: Stylomandibular Ligament StrainThis is usually felt as a sharp to aching pain in the region behind the jaw bone and below the ear. It can be a result of bad bite or from a traumatic injury Trismus : Trismus Masseter Hypertrophy : Masseter Hypertrophy Slide 54: Figure 2. Intraoral view showing midline deviation during occlusion. Slide 55: Masseter muscle hypertrophy is an asymptomatic,benign enlargement of one or both masseter muscles.
Etiology : Unclear, acc to several authors “emotional stress results in chronic forceful clenching of the jaws and bruxism, which cause a work hypertrophy of the muscle . “
LIPOMA, BENIGN OR MALIGNANT MUSCLE TUMORS,
BENIGN AND MALIGNANT MANDIBLE TUMORS. TEMPORAL MUSCLE HYPERTROPHY : TEMPORAL MUSCLE HYPERTROPHY Slide 57: TREATMENT:
Tranquilizers or muscle relaxants,
Psychiatric care and
Injection of very small doses of botulinum toxin type A.
Dental restorations and occlusal adjustments to correct premature contacts and malocclusions are important.
Parafunctional habits must be prevented.
Surgical removal of the hypetrophied muscle,
Partial removal of the muscle by modified liposuction techn ique.
Therapy needs to be specifically tailored for each patient, because the etiology of this condition is multifactorial INRAMUSCULARHEMANGIOMA : INRAMUSCULARHEMANGIOMA Slide 62: Hemangiomas of skeletal muscle represent 0.8% of all benign vascular neoplasm . Of these 13.8% occur in the head and neck region , with the masseter muscle being the most common site, followed by the trapezius and sternocleidomastoid muscles respectively.
Trauma (2) Congenital (3) Hormonal factors..
Cavernous (2)Capillary (3) Mixed.
The capillary type of hemangioma occurred more frequently in the head and neck region.
The cavernous and mixed types occurred more frequently in the trunk and lower limbs.
DIFFERENTIAL DIAGNOSIS: cysts, lymphangiomas, rhabdomyosarcomas, masseteric hypertrophy,
and schwannomas. Slide 63: Many treatment modalities like
have been advocated but the treatment of choice at present remains surgical excision MYOSITIS OSSIFICANS : MYOSITIS OSSIFICANS Slide 65: This is a benign conditon which results in reactive heterotopic
bone formation, usually producing limitation of opening of the jaws.
CLINICAL FEATURES: Limited mouth opening(trismus)
TYPES: MYOSITIS OSSIFICANS TRAUMATICA
MYOSITIS OSSIFICANS PROGRESSIVA
M O ASSOCIATED WITH PARAPLEGIA
M O ASSOCIATED WITH POLIOMYELITIS
ETIOPATHOLOGY: MOT; Trauma leads to intramuscular hemmorhage which results in reactive heterotrophic bone formation within the muscle.
T/T : Surgical removal of the abnormal mass. Slide 66: Panoramic radiograph indicating dense radiopaque mass extending from zygomatic arch to body and ramus of the left mandible. CT scan indicating a calcified mass in the left masseter muscle. CENTRONUCLEAR MYOPATHY : CENTRONUCLEAR MYOPATHY Centronuclear myopathy (CNM) is a rare form of congenital myopathy characterized by a universal involvement of the skeletal musculature leading to weakness and atrophy.Facial, masticatory, and extraocular muscles are characteristically involved Slide 68: This leads to fatty infiltration in masticatory muscles which leads to decrease in muscle mass and tone.
This can lead to fibrous ankylosis of TMJ which can further lead to true ankylosis.
TRETAMENT: Mouth opening exersices and surgical interventions References : References Sicher and Dubrull Oral anatomy 8th edition
Snell anatomy, Clinical anoatomy by Regions 8th edition..
B. D. Chaurasia.
Edmar Zanoteli, MD,a Antônio S. Guimarães, DDS...Temporomandibular joint involvement in a patient with centronuclear myopathy ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY Volume 90, Number 1
Keith Da Silva, BSc,a and Louis Mandel, DDS,b ,Bilateral temporalis muscle hypertrophy: A case report OOO, Volume 102, Number 1
Eduardo Kazuo SANNOMIYA1 Marcelo GONÇALVES2
Marcelo Paraíso CAVALCANTI3Masseter Muscle Hypertrophy - Case Report, Braz Dent J (2006) 17(4): 347-350.
C D Narayanan1*, Preeth Prakash2 and C K Dhanasekaran3, Intramuscular hemangioma of the masseter muscle: a case report,Cases journal.