TMJ-is the articulation between squamous part of temporal bone & the head of the condyle.

•Other terms of TMJ: 1.Temporomandibular articulation 2. Mandibular joint 3. Mandibular articulation 4. Craniomandibular articulation

>Is ginglymo-arthrodial joint 1. Gliding type-occurs between the articular disk & articular surface of temporal bone. 2. Hinge type- occurs between the inferior surface of the anterior disk & head of the condyle.

>Gliding motion is in the upper compartment of the joint between the disc and the temporal bone.

>Hinge movement is in the lower compartment of the joint between the disc and the condyle.

2 parts of temporal bone portion:• 1. Posterior articular fossa (mandibular fossa)• 2. Anterior articular tubercle

Bony components of TMJ:1. Head of the condyle2. Articular tubercle3. Glenoid fossa wall

Fibrous components:1. Articular fibrocartilage2. Articular disk3. Articular capsule

Histology:•The capsule of TMJ is composed of 2 layers:1.Outer layer- firm fibrous tissue reinforced by the ligaments associated with the joint.

2.Inner layer of the capsule( the synovial membrane)-thin connective tissue & contains blood vessels & nerves. *Synovial fluid produced by this layer both lubricates the joint & furnishes nourishment to joint parts that are without a blood supply: the fibrous covering of the articulating surfaces of the bones & the center of the disc.

•The disc- is composed of fibrous connective tissue.>older persons may have a few

• On the temporal bone, the part enclosed by the capsule of the TMJ-that is, the area of the articular fossa & eminence-is covered with fibrous connective tissue.

>This fibrous layer is thicker at the posterior border of the eminence than in the articular fossa. There are no blood vessels or nerves in this covering.

• On the mandibular condyle the articulating surface is covered with fibrous connective tissue similar to that covering the temporal bone area

>no blood vessels or nerves.>The fibrous layer is very thick on the uppermost part of the

curvature of the condyle.

• It is the fibrous connective tissue covering of the bone surfaces of the TMJ that makes this joint different from most other such articulations. Most such movable joints have a surface of hyalin cartilage rather than of fibrous connective tissue.

• Beneath the fibrous covering of the condyle of the fetus is hyalin cartilage. This is a growth center, & in this location the cartilage increases almost entirely by appositional growth (new cartilage added to existing cartilage edges).

• As dev. continues the cartilage is gradually replaced by bone: compact bone forms under the fibrous connective tissue covering, & trabecular bone replaces the cartilage within the mandibular head: the condyle takes on the adult histologic form.

• Growth of the condylar cartilage affects the height & length of the mandible & influences the shape of the entire face.

• The TM capsule is reinforced by ligamentous thickenings. Ligaments are non-elastic collagenous structures that restrict & limit the movements a joint can make in that they limit the distance that the bones forming the articulation can be separated from each other without causing tissue damage.

• Functional ligament associated with TMJ:>Lateral or Temporomandibular ligament-fan-shaped

reinforcement of the lateral wall of the capsule running obliquely backward & downward from the lateral aspect of the articular eminence to the posterior aspect of the condylar neck

* prevents lateral & medial dislocation of the opposite joint.

This ligament consists of 2 parts:1.Outer oblique portion-arises from the outer surface of the articular eminence & extending backward & downward to insert into the outer surface of the condylar neck. *limits the amount of inferior displacement that can occur.2. Inner horizontal portion- with the same origin but inserting into the lateral pole of the condyle & the lateral margin of the disk.* limits posterior displacement of the condyle & disk.

• Maxillary sinus is the pneumatic space that is lodged inside the body of the maxilla & that communicates with the environment by way of the middle nasal meatus & the nasal vestibule.

>described as a four-sided pyramid, the base of which is facing medially toward the nasal cavity & the apex of which is pointed laterally toward the body of the zygomatic bone.

The 4 sides are related to the surface of the maxilla in the following manner: 1.anterior, to the facial surface of the body2. inferior, to the alveolar & zygomatic processes3.superior, to the orbital surface4.posterior, to the infratemporal surface.

The four sides of the sinus, which are usually distant from one another medially, converge laterally & meet at an obtuse angle.

3 Distinct layers that surrounds the space:

1. Epithelial layer2. Basal lamina3. Subepithelial layer, including the periosteum

>The epithelium, which is pseudostratified, columnar, & ciliated.

>The most numerous cellular type in the maxillary sinus epithelium is the columnar ciliated cell.

Importance:• Air is arrestred in the sinus for a certain time, it quickly reaches body temperature & thus protects the internal structures, particularly the brain, against exposure to cold air.• Resonance of voice•Lightening of the skull weight.•Enhancement of faciocranial resistance to mechanical shock.•Production of bactecidal lysozyme to the nasal cavity.

Clinical Considerations:1.Pituitary giantism- all sinuses assume a much larger volume than in healthy individuals.

2. Spirochetes in congenital syphilis, the pneumatic processes are greatly suppressed, resulting in small sinuses.

3. The transfer of a pathologic condition from the sinus to the orodental apparatus, or vice versa, is achieved either by mechanical connections or by way of the blood or lymphatic pathways.

4. The chronic infections of the mucoperiosteal layer of the sinus might involve superior alveolar nerves, if these nerves are closely related to the sinus, & cause the neuralgia that mimics possible dental origin.

5. Malignant lesions (adenocarcinoma, squamous cell carcinoma, osteosarcoma, fibrosarcoma, lymphosarcoma) of the maxillary sinus may produce their primary manifestation in the maxillary teeth. This may consist of pain, loosening, supraeruption, or bleeding in their gingival tissue.