The Temporalmandibular Joint (TMJ) The joint formed between the mandibular fossa of the temporal bone and the mandibular condyle of the mandible. There is a disc that lies between them, surrounded by a joint capsule 80-90% of the population have TMJ problems – only 5% seek help It is the most over-used joint in the body VERY DIFFICULT JOINT TO TREAT!!!

Movements Protraction/Retraction Mandibular elevation/depression Deviation Laterally/contralaterally

The Articular Disc Biconcave Allows for gliding to occur at the TMJ The Lateral Pterygoid is attached to it anteriorly

The Capsule Is lax and thin to allow for the greatest ROM Therefore a tight and damaged capsule = decreased ROM Capsule of the TMJ is innervated very well – There is a lot of proprioceptive input received by the TMJ

Ligaments Lateral (Temporomandibular) Ligament From the zygomatic process to the neck of the Mandible Runs down and backwards to form the thickening of the capsule Sphenomandibular Ligament From the spine of the sphenoid to the middle aspect of the mandible (on the internal surface) Runs down and forward

Ligaments Stylomandibular Ligament From the styloid process of the temporal bone to the angle of the mandible Pterygo-Mandibular Ligament Actually a thickening of buccinator

Muscles of the TMJ Major muscles of mastication: Temporalis Masseter Lateral pterygoid Medial pterygoid

Muscles of the TMJ (cont’d.) Lesser muscles of mastication—the hyoid group: SuprahyoidsInfrarahyoids Digastric Sternothyroid Mylohyoid Sternohyoid Geniohyoid Thyrohyoid Stylohyoid Omohyoid

Superficial Right Lateral View of the Muscles of the Head

View of the Major Muscles of Mastication

Views of the Major Muscles of Mastication (cont’d)

Anterior View of the Neck and the Upper Chest

Anterior Views of the Neck and the Upper Chest—Head Extended

Temporalis—Lateral View

Temporalis: Attachments Origin: The entire temporal fossa except the portion of the zygomatic bone Insertion: Coronoid process and the ramus of the mandible The anterior border, apex and posterior border and internal surface of the coronoid process of the mandible, as well as the anterior border of the ramus of the mandible Nerve: The Trigeminal Nerve (CN 5)

Temporalis: Actions What joint does this muscle cross? It crosses the temporomandibular joints (TMJs). How does the temporalis cross the TMJs? The temporalis crosses the TMJs vertically. If the temporalis crosses the TMJs with a vertical direction to its fibers, what action will it have? Elevates the mandible at the temporomandibular joints (TMJs)

Temporalis: Review— Lateral View

Masseter—Lateral View

Masseter (cont’d.)—Lateral View

Masseter: Attachments Origin: SUPERFICIAL LAYER: Inferior margins of the zygomatic bone and the zygomatic arch DEEP LAYER: the inferior margin and the deep surface of the zygomatic arch Insertion: SUPERFICIAL LAYER: The angle and the inferior ½ of the external surface of the ramus of the mandible DEEP LAYER: The external surface of the coronoid process and the superior half of the external surface of the ramus of the mandible Nerve: The Trigeminal Nerve (CN 5)

Masseter: Actions What joint does this muscle cross? The masseter crosses the temporomandibular joints (TMJs). How does the masseter cross the TMJs? The masseter crosses the TMJs vertically. If the masseter crosses the TMJs with a vertical direction to its fibers, what action will it have? Elevates the mandible at the temporomandibular joints (TMJs)

Masseter: Review—Lateral View

Lateral Pterygoid—Lateral View

Lateral Pterygoid (cont’d.)— Posterior View

Lateral Pterygoid: Attachments Origin: SUPERIOR HEAD: The greater wing of the sphenoid INFERIOR HEAD: The lateral surface of the lateral pterygoid plate of the pterygoid process of the sphenoid Insertion: SUPERIOR HEAD: The capsule and the articular disc of the temporomandibular joint (TMJ) INFERIOR HEAD: The neck of the mandible Nerve: The Trigeminal Nerve (CN 5)

Lateral Pterygoid: Actions What joint does this muscle cross? It crosses the TMJs. Where does the lateral pterygoid cross the TMJs? The lateral pterygoid crosses the TMJs anteriorly. How does the lateral pterygoid cross the TMJs? The lateral pterygoid crosses the TMJs horizontally. If the lateral pterygoid crosses the TMJs anteriorly with a horizontal direction to its fibers, what action will it have? The lateral pterygoid will protract the mandible at the TMJs. The lateral pterygoid can also contralaterally deviate the mandible because its sphenoid attachment is medial to the mandibular attachment. Why is lateral deviation of the mandible important? Lateral deviation of the mandible at the TMJs is important for chewing food. Although all four muscles of mastication could be involved in TMJ syndrome, the lateral pterygoid is often the most likely suspect

Lateral Pterygoid: Review— Lateral View

Lateral Pterygoid: Review

Medial Pterygoid—Lateral View

Medial Pterygoid (cont’d.)— Posterior View

Medial Pterygoid: Attachments Origin: DEEP HEAD: The medial surface of the lateral pterygoid plate of the pterygoid process of the sphenoid, the palatine bone and the tuberosity of the maxilla SUPERFICIAL HEAD: The palatine bone and the maxilla Insertion: Internal surface of the mandible at the angle of the mandible and the inferior border of the ramus of the mandible Nerve: The Trigeminal Nerve (CN 5)

Medial Pterygoid: Actions What joint does this muscle cross? The medial pterygoid crosses the temporomandibular joints (TMJs). How does the medial pterygoid cross the TMJs? The medial pterygoid crosses the TMJs vertically. With what muscle is the medial pterygoid essentially parallel?. TRelative to the TMJ, the direction of the fibers of the medial pterygoid is virtually the same as the direction of the fibers of the masseter Therefore what action will they both have at the mandible at the TMJs? Elevation of the mandible at the temporomandibular joints (TMJs)

Medial Pterygoid: Actions The difference between the masseter and the medial pterygoid is that the masseter is external (lateral) to the mandible, whereas the medial pterygoid is internal (medial) to the mandible. The other attachment of the medial pterygoid is superior, anterior, and medial to the mandibular attachment, hence the medial pterygoid elevates, protracts, and contralaterally deviates the mandible.

Medial Pterygoid: Review— Lateral View

Hyoid Bone Not a bone of the skull Does not articulate directly with another bone Site of attachment for muscles of swallowing and speech

Hyoids A group of 8 muscles that are superficial on the anterior neck. They are subdivided into two groups of four: 1) Suprahyoids: Digastric Stylohyoid Mylohyoid Geniohyoid The suprahyoids are located superior to the hyoid bone. As a group, the suprahyoids elevate the hyoid bone.

Hyoids 2) Infrahyoids: Sternohyoid Sternothyroid Thyrohyoid Omohyoid The infrahyoids are located inferior to the hyoid bone. As a group, the infrahyoids depress the hyoid bone. Therefore, the suprahyoids and the infrahyoids can be considered antagonistic sets of muscles. However, the two groups can be contracted synergistically to fix the hyoid bone as a stable base for depressing the mandible and flexing the neck at the spinal joints.

Digastric—Anterior View

Digastric (cont’d.)—Right Lateral View

Digastric: Attachments Origin: Posterior belly - the mastoid notch of the temporal bone Anterior belly - The inner surface of the inferior border of the mandible (the digastric fossa) Insertion: The central tendon of the Hyoid Bone (There is a central tendon that is bound to the hyoid bone at the body and the greater cornu) Nerve: Trigeminal Nerve (CN 5) Anterior belly Facial Nerve (CN 7) Posterior belly

Digastric: Actions Depresses the mandible at the temporomandibular joints (TMJs) The digastric is considered to be the prime mover of depression of the mandible at the TMJs. Flexes the head and the neck at the spinal joints When it contracts it would pull the hyoid bone superiorly, elevating the hyoid.

Digastric: Review—Anterior View

Mylohyoid—Anterior View

Mylohyoid (cont’d.)— Right Lateral View

Mylohyoid: Attachments Origin: The mylohyoid line on the inner surface of the mandible (from the symphysis menti to the molars) The mylohyoid helps to form the floor of the mouth (oral cavity). Insertion: The anterior surface of the body of the Hyoid Nerve: The Trigeminal Nerve (CN 5)

Mylohyoid: Actions Depresses the mandible at the temporomandibular joints (TMJs) Flexes the head and the neck at the spinal joints Elevates the hyoid

Mylohyoid: Review— Anterior View

Geniohyoid—Anterior View

Geniohyoid (cont’d.)—Right Lateral View

Geniohyoid: Attachments Origin: The inferior mental spine located on the inner surface of the mandible Insertion: The anterior surface of the body of the Hyoid Nerve: The Hypoglossal Nerve (CN 12)

Geniohyoid: Actions Depresses the mandible at the temporomandibular joints (TMJs) Flexes the head and neck at the spinal joints Elevates the hyoid

Geniohyoid: Review— Anterior Views

Stylohyoid—Anterior View

Stylohyoid (cont’d.)— Right Lateral View

Stylohyoid: Attachments Origin: The posterior surface of the styloid process of the temporal bone Insertion: Hyoid bone at the junction of the body and the greater cornu of the hyoid bone Nerve: The Facial Nerve (CN 7)

Stylohyoid: Actions Elevates the hyoid When the stylohyoid contracts, it would pull the hyoid bone superiorly toward the styloid process of the temporal bone, elevating the hyoid. The stylohyoid can also retract the hyoid bone (draw the hyoid bone posteriorly).

Stylohyoid: Review—Anterior View

Sternohyoid—Anterior View

Sternohyoid: Attachments Origin: The posterior surface of both the manubrium of the sternum and the medial clavicle Insertion: The inferior surface of the body of the Hyoid Nerve: Cervical Plexus C1, C3

Sternohyoid: Actions Depresses the hyoid Flexes the neck and head at the spinal joints

Sternohyoid: Review— Anterior View

Sternothyroid—Anterior View

Sternothyroid: Attachments Origin: The posterior surface of both the manubrium of the sternum and the cartilage of the 1 st rib Insertion: The Thyroid cartilage Nerve: The Cervical Plexus C1, C3

Sternothyroid: Actions Depresses the thyroid cartilage Flexes the neck and head at the spinal joints Movements of the thyroid cartilage are important in chewing, swallowing, and speech.

Sternothyroid: Review— Anterior View

Thyrohyoid—Anterior View

Thyrohyoid: Attachments Origin: Thyroid cartilage Insertion: The inferior surface of the greater cornu of the Hyoid Nerve: The Hypoglossal Nerve (CN 12)

Thyrohyoid: Actions Depresses the hyoid The thyrohyoid pulls the hyoid bone inferiorly toward the thyroid cartilage, depressing the hyoid. Flexes the neck and head at the spinal joints

Thyrohyoid: Review— Anterior View

Omohyoid—Anterior View

Omohyoid: Attachments Origin: The inferior belly : The superior border of the scapula The superior belly: The central tendon which is bound to the clavicle Insertion: The inferior belly : The central tendon which is bound to the clavicle The superior belly: The inferior surface of the body of the hyoid Nerve: Cervical Plexus C1-C3

Omohyoid: Actions Depresses the hyoid When the omohyoid contracts, it pulls the hyoid bone inferiorly toward the scapula, depressing the hyoid. The omohyoid has the somewhat unique feature that it does not run in a straight line from its scapular attachment to its hyoid bone. Instead, it turns about a “pulley” created by a fibrous sling of tissue that attaches to the clavicle. Flexes the neck and head at the spinal joints

Omohyoid: Review— Anterior View