Skeletal System: Articulations

This set of vocabulary flashcards covers the motions of synovial joints, the terminology and classes of levers in the body, and the specific anatomy of the temporomandibular joint (TMJ).

Gliding

A movement where two opposing surfaces slide back-and-forth or side-to-side with only limited movement possible in any direction, typically occurring along plane joints like those between carpals or tarsals.

Angular motion

A type of motion that increases or decreases the angle between two bones, including movements such as flexion, extension, abduction, and adduction.

Flexion

Movement in an anterior-posterior plane that decreases the angle between bones, bringing the bones closer together.

Extension

Movement in an anterior-posterior plane that increases the angle between articulating bones, representing the opposite of flexion.

Hyperextension

The extension of a joint beyond its normal range of motion.

Lateral flexion

Movement of the trunk of the body laterally in the coronal plane, specifically occurring between vertebrae in the cervical and lumbar regions.

Abduction

Lateral movement of a body part away from the midline of the body.

Adduction

Medial movement of a body part toward the midline of the body.

Circumduction

A sequence of movements where the proximal end of an appendage remains relatively stationary while the distal end makes a circular motion, creating an imaginary cone shape.

Rotation

A motion where a bone pivots on its own longitudinal axis.

Pronation

Medial rotation of the forearm so the palm of the hand is directed posterior.

Supination

Lateral rotation of the forearm so the palm of the hand is directed anterior.

Depression

The inferior movement of a body part, such as moving the mandible while opening the mouth.

Elevation

The superior movement of a body part, such as moving the mandible while closing the mouth.

Dorsiflexion

A movement limited to the talocrural (ankle) joint where the superior surface of the foot moves toward the leg.

Plantar flexion

A movement at the talocrural joint where the dorsum of the foot is pointed inferiorly, such as a ballet dancer standing on tiptoes.

Eversion

A movement occurring only at the intertarsal joints of the foot where the sole turns laterally.

Inversion

A movement occurring only at the intertarsal joints of the foot where the sole turns medially.

Protraction

Anterior movement of a body part from the anatomic position, such as jutting the jaw anteriorly.

Retraction

Posterior movement of a body part from the anatomic position, such as pulling the jaw posteriorly.

Opposition

Movement of the thumb toward the tips of the fingers at the carpometacarpal joint, enabling the grasping of objects.

Biomechanics

The practice of applying mechanical principles to biology.

Lever

An elongated, rigid object that rotates around a fixed point called a fulcrum.

Effort arm

The part of a lever from the fulcrum to the point of effort.

Resistance arm

The part of a lever from the fulcrum to the point of resistance.

First-Class Lever

A lever where the fulcrum is between the effort and the resistance, such as the atlanto-occipital joint of the neck.

Second-Class Lever

A lever where the resistance is between the fulcrum and the effort, such as when standing on tiptoe.

Third-Class Lever

The most common lever in the body, where the effort is applied between the resistance and the fulcrum, such as at the elbow joint.

Temporomandibular Joint (TMJ)

The only mobile joint between bones in the skull, where the head of the mandible articulates with the temporal bone.

Articular disc

A thick pad of avascular dense regular connective tissue in the TMJ that divides the synovial cavity into two chambers.

Sphenomandibular ligament

A ligament of the TMJ that extends anteriorly and inferiorly from the sphenoid to the mandible.

Temporomandibular ligament

A ligament that extends inferiorly and posteriorly from the articular tubercle to the mandible.