The Temporomandibular Joint

• This articulation is a modified hinge type of synovial joint.
• The articular surfaces are: (1) the head or condyle of the mandible inferiorly and (2) the articular tubercle and the mandibular fossa of the squamous part of the temporal bone.

• An oval fibrocartilaginous articular disc divides the joint cavity into superior and inferior compartments. The disc is fused to the articular capsule surrounding the joint.

• The articular disc is more firmly bound to the mandible than to the temporal bone.

• Thus, when the head of the mandible slides anterior on the articular tubercle as the mouth is opened, the articular disc slides anteriorly against the posterior surface of the articular tubercle

• Ossification

• Intramembranous-found in the flat bones of the face
  • Mesenchymal cells cluster and form strands
  • Strands are cemented in a uniform network. Which is known as osteoid
  • Calcium salts are deposited; osteoid is converted to bone
  • Trabeculae are formed and make cancellous bone with open spaces known as marrow cavities
  • Periosteum forms on the inner and outer surfaces of the ossification centers
  • Surface bone becomes compact bone
• Endochondral-primary type of ossification In the human

• Bones begin to form during the eighth week of embryomic life in the fibrous membranes (intramembranous ossification) and hyaline cartilage (endochondral ossification)

The Muscles of Facial Expression

• These lie in the subcutaneous tissue and are attached to the skin of the face.
• They enable us to move our skin and change our facial expression. They produce their effects by pulling on the skin but do not move the facial skeleton.
• These muscles surround the facial orifices and act as sphincters and dilators.
• All facial muscles receive their innervation from the branches of the facial nerve (CN VII)-temporal, zygomatic, buccal, marginal mandibular, cervical.

Stylohyoid Muscle

• Origin: Posterior border of the styloid process of the temporal bone.
• Insertion: Body of the hyoid bone at the junction with the greater horn.
• Nerve Supply: Facial nerve (CN VII).
• Arterial Supply: Muscular branches of the facial artery and muscular branches of the occipital artery.
• Action: Elevates the hyoid bone and base of the tongue.

The Lateral Wall of the Orbit

• This wall is thick, particularly its posterior part, which separates the orbit from the middle cranial fossa.
• The lateral wall is formed by the frontal process of the zygomatic bone and the greater wing of the sphenoid bone.

• Anteriorly, the lateral wall lies between the orbit and the temporal fossa.

• The lateral wall is partially separated from the roof by the superior orbital fissure.