Chapter 11: Joints of the Skull

Fetal Skull

Bones are not completely ossified at birth

Hinge movements of TMJ

-Depression: inferior movement of the mandible (open mouth) -Elevation: superior movement of the mandible (close mouth)

Anterior fontanelle

-Largest fontanelle located at the junction of the coronal and sagittal sutures. -In adults, this lies at the location of the bregma. - in babies called the "soft spot"

Planar movements of the TMJ

-Protraction: anterior movement of the mandible in a horizontal plane -Retraction: posterior movement of the mandible in a horizontal plane -Lateral movement: side-to-side movement (grinding)

Skull Sutures: classification & bony surfaces

-fibrous joints (suture in type), no ligaments or movement -sagittal suture -frontal (coronal) suture -lambdoid suture -squamous suture

Temporomandibular joint (TMJ): classification

-synovial joint, combined hinge and plane

Physician's use the anterior fontanelle to determine:

1. Position of fetal head in utero 2. The development of the skull (becomes bony at 2 years of age, unlike the other fontanelles which ossify within a few months) 3. Extent of pathological intracranial pressure

Two compartments of the joint cavity

1. Superior compartment: located between the articular disc and the mandibular fossa 2. Inferior compartment: located between the articular disc and mandible

Two types of movemenets at the TMJ

Hinge movements & planar movements

Bony surfaces of TMJ

Mandibular fossa of the temporal bone Head (condyloid process) of the mandible

Fontanelles

Six major unossified, membranous areas between the cranial bones

Anterolateral fontanelles (sphenoid fontanelles)

Small irregular fontanelles located at the junction of the frontal, parietal, sphenoid, and temporal bones

Posterolateral fontalles (mastoid fontanelles)

Small irregular fontanelles located at the junction of the occipital, parietal, and temporal bones

Sagittal suture

The articulation of the two parietal bones in the median plane of the skull

Posterior fontanelle

Triangular; located at the junction of the lambdoid and sagittal sutures. -in adults, lies at the location of the lambda

Articular disc

prominent intraarticular ligament of TMJ -oval plate of fibroud tissue, sometimes contains patches of fibrocartilage -circumference of the disc attaches to the articular capsule -divides the joint cavity into two separate compartments

squamous suture

the articulation of the parietal and temporal bones

lambdoid suture

the articulation of the parietal bones with the occipital bone

frontal (coronal) suture

the articulation of the partietal bones with the frontal lobe