The temporomandibular joint (TMJ) is a diarthrosis, better defined as a ginglymoarthrodial joint, with 4 articular spaces. TMJ is composed of a synovial cavity, articular cartilage and a capsule that covers the same joint. The cranial surface of TMJ consists of the squamous area of the temporal bone; it takes the name of glenoid fossa and welcomes the condyle of the jaw. The posterior area of the fossa is known as posterior articular ridge; sideways to the latter, we find a bone portion called postglenoid process. The postglenoid process area contributes to forming the upper wall of the external acoustic meatus. (Bordoni 2021)
[Alomar et al, 2007]
Mandibular Component
Cranial Component: The roof of the mandibular fossa, which separates it from the middle cranial fossa, is always thin and translucent, even in the heavy skull. This demonstrates that, although the articular fossa contains the posterior rim of the disk and the condyle, it is not a functionally stress-bearing part of the craniomandibular articulation.
The articular disc that covers the condyle and interposes below the glenoid fossa has a biconcave or oval shape; the cartilaginous disc has an anterior (about 2 mm) and posterior (about 3 mm) portion, with a thinner diameter in the middle. The anterior portion of the disk consists of a layer of fibroelastic fascia (above) and a fibrous layer (inferiorly). The upper portion is in contact with the postglenoid process to prevent the disc from slipping during the opening of the mouth. The lower portion of the disk has the task of avoiding excessive rotational movements of the disk relative to the mandibular condyle.(Bordoni 2021)
The normal posterior attachment of the disc is usually described as having two layers, one upper and one lower. The upper layer consists of elastic fibers, collagen fibers, fat deposits and blood vessels. It is connected posteriorly to the anterior face of the post-glenoid tubercle, the tympanic wall of the temporal bone, the cartilaginous meatus and the parotid gland lining. The lower layer, on the other hand, consists of a compact lamina of non-elastic collagen fibers, attached to the posterior surface of the condyle. (Barlattani et al,2019)
Bilaminar zone: In an histological study done in 1989, Kino et al described the retrodiscal area as follows: the area was composed of the collagen fibers originating into this area from the petrotympanic fissure, from the conjunctive area of the posterior wall of the fossa with the lateral wall of the articular cavity, and from the conjunctive area of the posterior slope of the auricular tubercle with the lateral wall of the articular cavity. In the superficial layer of the retrodiscal area, these fibers crossed each other, and a few fibers jointed with these fibers from the superficial layer of the disk and from the posterior wall of the articular fossa. The arrangement of these fibers had various directions, however most of fibers tended to run medio-laterally. The fiber bundles containing many elastic fibers ran into the retrodiscal area from the petrotympanic fissure. Although these fibers connected the most medial side of the disk with the medial side of the posterior wall of the articular fossa, they had many branches composing the retrodiscal area as stayed above.
Benigno et al in 2001 described it as follows: The bilaminar zone (BZ) in the human temporomandibular joint (TMJ) of toothed adults (GI) and toothless, elderly humans (GII) were analysed using light and scanning electron microscopy (SEM). In both groups the BZ consists of an upper and a lower stratum of connective tissue separated by a vascularized middle region. The elastic fibres lie parallel to the collagen fibres in both groups and they are thicker and more abundant in GI, apparently decreasing in GII.
The disc divides the TMJ into two compartments: Superior (translational movement) and inferior compartments (rotational movement):
Several ligaments manage the TMJ forces and send multiple proprioceptive afferents. (Bordoni 2021)
Synovial fluid is viscous and has lubricating, metabolic, and regulatory functions within synovial joints. Cytokines and growth factors are present in synovial fluid and are important regulatory factors for the immune and metabolic systems in the joint. (Kristensen, 2014).
It has been reported that the synovial fluid pressure is subatmospheric when the jaw is in a resting position, and the pressure increases as a result of joint movement or disorders. During cyclic jaw movements, the synovial fluid reaches all necessary cartilage regions as a result of the normal pressure distribution. (Xu et al, 2012).
Several studies have reported that synovial inflammation may be related to the initial stage of a disorder of the TMJ in which inflammatory cytokines, matrix metalloproteases, 45 disintegrin, and metalloproteinase with thrombospondin motifs are increased, leading to enzymatic degradation of the cartilage matrix, particularly in osteoarthritis. (Ishimaru et al, 2015).
Sensory innervation of the temporomandibular joint is derived from the auriculotemporal and masseteric branches of V3 or mandibular branch of the trigeminal nerve.
The auriculotemporal nerve trunk has a close anatomic relationship with the condyle and the temporomandibular joint capsular region, and there is evidence of a possible mechanism for sensory disturbances in the temporomandibular joint region.
| NERVE (V3) |
| Auriculotemporal (main supply) |
| Masseteric |
| Posterior deep temporal |
Parasympathetic fibers of the otic ganglion stimulate synovial production. Sympathetic neurons from the superior cervical ganglion reach the joint along the vessels and play a role in pain reception and the monitoring of the blood volume.
Arterial supply:
| Superficial temporal (external carotid) |
| Deep auricular (Maxillary |
| Anterior tympanic (Maxillary) |
Venous supply:
| Superficial temporal |
| Maxillary |
The temporomandibular joint (TMJ): Anatomy and supply | Kenhub
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Kristensen KD, Alstergren P, Stoustrup P, Küseler A, Herlin T, Pedersen TK. Cytokines in healthy temporomandibular joint synovial fluid. J Oral Rehabil. 2014 Apr;41(4):250-6. doi: 10.1111/joor.12146. Epub 2014 Feb 27. PMID: 24575711.
Schmidt BL, Pogrel MA, Necoechea M, Kearns G. The distribution of the auriculotemporal nerve around the temporomandibular joint. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1998 Aug;86(2):165-8. doi: 10.1016/s1079-2104(98)90119-6. PMID: 9720090.
Kino K, Ohmura Y, Kurokawa E, Shioda S. [Reconsideration of the bilaminar zone in the retrodiscal connective tissue of the TMJ. 2. Fibrous structure of the retrodiscal connective tissue and relation between those fibers and the disk]. Nihon Ago Kansetsu Gakkai Zasshi. 1989;1(2):43-54. Japanese. PMID: 2485145.
Benigno MI, Azeredo RA, Lemos JL, König Júnior B, Liberti EA. The structure of the bilaminar zone in the human temporomandibular joint: a light and scanning electron microscopy study in young and elderly subjects. J Oral Rehabil. 2001 Feb;28(2):113-9. doi: 10.1046/j.1365-2842.2001.00683.x. PMID: 11298258.