Human Anatomy - Temporomandibular Joint Lecture 10 (Almaaqal University) PDF

Academic year 2023-2024 ‫فرع جراحة الفم والوجه والفكين‬ ‫كلية طب االسنان‬ 2ed year...

Academic year 2023-2024 ‫فرع جراحة الفم والوجه والفكين‬ ‫كلية طب االسنان‬ 2ed year Human Anatomy Lecture 10 Temporomandibular joint By: Dr. Nada hashim AL JASSIM Snell R.S. Clinical Anatomy by regions, 9th Edition, Lippincott Williams & Wilkins, [2012 For more detailed instructions, any question, cases need help please post to the telegram group of the session  Temporomandibular joint The temporomandibular joint (TMJ) is a modified hinge type of synovial joint, permitting gliding (translation) and a small degree of rotation (pivoting) in addition to flexion (elevation) and extension (depression) movements typical for hinge joints. The bony articular surfaces involved are the mandibular fossa and articular tubercle of the temporal bone superiorly, and the head of the mandible (condylar process) inferiorly.Unlike most synovial joints, its articular surfaces are covered with fibrous cartilage rather than hyaline cartilage and the joint cavity is divided by a fibrocartilaginous articular disc into upper and lower cavities. A dissection of the left temporomandibular joint.  The Articular Disk The articular disk is composed of dense fibrous connective tissue and is non-vascularized and non-innervated, an adaptation that allows it to resist pressure. Anatomically the disk can be divided into three general regions: the anterior band, the central intermediate zone, and the posterior band. The intermediate zone is thinnest and is generally the area of function between the mandibular condyle and the temporal bone. Retro discal Tissue Posteriorly the articular disk blends with a highly vascular, highly innervated structure (the bilaminar zone), which is involved in the production of synovial fluid.The superior aspect of the retrodiskal tissue, termed the superior retrodiskal lamina, contains elastic fibers attached to the tympanic plate and act as a restraint to disk movement in extreme translator movements. The inferior aspect of the retrodiskal tissue, termed the inferior retrodiskal lamina, consists of collagen fibers connected to the posterior margin of the condyle and thought to serve to prevent extreme rotation of the disk on the condyle in rotational movements. The meniscus and retrodiscal tissue. Capsule The capsule surrounds the joint and is attached above to the articular tubercle and the margins of the mandibular fossa and below to the neck of the mandible. It permits side to- side motion, protrusion, and retrusion. The two bony articular surfaces are completely separated by intervening fibrocartilage, the articular disc of the TMJ (Meniscus), attached at its periphery to the internal aspect of the fibrous capsule. This creates separate superior and inferior articular cavities, or compartments, lined by separate superior and inferior synovial membranes. Temporomandibular joint (TMJ). A–D: Anatomical and CT images of the TMJ in the closed- and open-mouth positions. E: Innervation of TMJ. Synovial Membrane The synovial membrane is a thin, smooth, richly innervated vascular tissue (without an epithelium) that lines the capsule.Lining the inner aspect of all synovial joints, including the TMJ, are two types of tissue: articular cartilage and synovium. The space bound by these two structures is termed the synovial cavity, which is filled with synovial fluid that contains a high concentration of hyaluronic acid that is thought to be responsible for the fluid’s high viscosity. The synovium is capable of rapid and complete regeneration following injury. Functions of the synovial fluid include lubrication of the joint, phagocytosis of particulate debris, and nourishment of the articular cartilage. The concentration of hyaluronic acid and hence the viscosity of the synovial fluid is greater at the point of load, thus protecting the articular surfaces. Temporomandibular joint with mouth closed (A) and with the mouth open (B). (C): The attachment of the muscles of mastication to the mandible. The arrows indicate the direction of their actions. Ligaments The lateral temporomandibular ligament strengthens the lateral aspect of the capsule, and its fibers run downward and backward from the tubercle (in the root of zygoma) to the lateral surface of the neck of the mandible.This ligament limits the movement of the mandible in a posterior direction and thus protects the external auditory meatus. Ligaments of temporomandibular joint. The articular disc divides the joint into upper and lower cavities. It is an oval plate of fibrocartilage that is attached circumferentially to the capsule. It is also attached in front to the tendon of the lateral pterygoid muscle and by fibrous bands to the head of the mandible. These bands ensure that the disc moves forward and backward with the head of the mandible during protraction and retraction of the mandible. The upper surface of the disc is concavo- convex from before backward to fit the shape of the articular tubercle and the mandibular fossa; the lower surface is concave to fit the head of the mandible. The stylomandibular ligament lies behind and medial to the joint and extends from the apex of the styloid process to the angle of the mandible.This ligament limits anterior protrusion of mandible. The sphenomandibular ligament lies on the medial side of the joint.It is a thin band that is attached above to the spine of the sphenoid bone and below to the lingula of the mandible. This ligament may act as a pivot by providing tension during opening and closing. Ligaments of temporomandibular joint. Nerve Supply The nerve supply to the TMJ is predominantly from branches of the auriculotemporal nerve with anterior contributions from the masseteric nerve and the posterior deep temporal nerve. Vascular Supply The vascular supply of the TMJ arises primarily from branches of the superficial temporal and maxillary arteries posteriorly and the masseteric artery anteriorly. There is a rich plexus of veins in the posterior aspect of the joint, which alternately fill 4 and empty with protrusive and retrusive movements respectively, and which also function in the production of synovial fluid. Movements TMJ movements are produced chiefly by the muscles of mastication. The mandible can be depressed or elevated, protruded or retracted. Rotation can also occur, as in chewing. In the position of rest, the teeth of the upper and lower jaws are slightly apart. On closure of the jaws, the teeth come into contact. Generally, depression of the mandible is produced by gravity. The suprahyoid and infrahyoid muscles are primarily used to raise and depress the hyoid bone and larynx.Indirectly they can also help depress the mandible, especially when opening the mouth suddenly, against resistance, or when inverted (e.g., standing on one’s head). The platysma can be similarly used. Important Relations of the Temporomandibular Joint Anteriorly: The mandibular notch and the masseteric nerve and artery. Posteriorly: The tympanic plate of the external auditory meatus and the glenoid process of the parotid gland Laterally: The parotid gland, fascia, and skin. Medially: The maxillary artery and vein and the auriculotemporal nerve. Movements of temporomandibular joint Clinical Notes The temporomandibular joint lies immediately in front of the external auditory meatus. The great strength of the lateral temporomandibular ligament prevents the head of the mandible from passing backward and fracturing the tympanic plate when a severe blow falls on the chin. The articular disc of the temporomandibular joint may become partially detached from the capsule, and this results in its movement becoming noisy and producing an audible click during movements at the joint. Dislocation of TMJ Sometimes during yawning or taking a large bite, excessive contraction of the lateral pterygoids may cause the heads of the mandible to dislocate anteriorly (pass anterior to the articular tubercles).In this position, the mandible remains depressed and the person is unable to close his or her mouth and the condition can be quite painful. Posterior dislocation is uncommon, being resisted by the presence of the post glenoid tubercle and the strong intrinsic lateral ligament. Dislocation of temporomandibular joint Reduction of the dislocation is easily achieved by pressing the gloved thumbs downward on the lower molar teeth and pushing the jaw backward. The downward pressure overcomes the tension of the temporalis and masseter muscles, and the backward pressure overcomes the spasm of the lateral pterygoid muscles. Surgery of TMJ Because of the close relationship of the facial and auriculotemporal nerves to the TMJ, care must be taken during surgical procedures to preserve both of them. Injury to these nerves usually leads to laxity and instability of the TMJ. Arthritis of TMJ The TMJ may become inflamed from degenerative arthritis. Abnormal function of the TMJ may result in structural problems such as dental occlusion and joint clicking (crepitus). The clicking is thought to result from delayed anterior disc movements during mandibular depression and elevation.. THANK YOU