Module 8.1: Overview and Classification of Joints

Vocabulary practice flashcards covering Module 8.1: joint functional and structural classifications, anatomy of synovial joints, supportive structures, forms of arthritis, types of synovial joint movements, and the six structural types of synovial joints.

Synarthrosis

A functional joint classification characterized by no movement between articulating bones, providing the greatest stability (e.g., skull bones).

Amphiarthrosis

A functional joint classification that allows only a small amount of movement while providing joint stability.

Diarthrosis

A functional joint classification that is freely moveable, allowing a wide variety of specific movements while providing the least amount of stability.

Fibrous joints

Joints where bones are united by short collagen fibers of dense regular collagenous connective tissue without a joint space; functionally classified as synarthroses or amphiarthroses.

Cartilaginous joints

Joints where articulating bones are held together by cartilage without a joint space; functionally classified as synarthroses or amphiarthroses.

Synovial joints

The only class of joints to feature a fluid-filled joint cavity or space between articulating bones; functionally classified as diarthroses.

Sutures

Immovable fibrous joints (stable synarthroses) between the bones that make up the skull, joined by dense regular collagenous connective tissue.

Synostosis

The complete bony fusion of articulating bones that replaces the fibrous joint tissue of a suture.

Gomphoses

Immovable fibrous joints (synarthroses) located between a tooth and its corresponding alveolus in the maxilla or mandible.

Periodontal ligament

Dense regular collagenous connective tissue fibers that firmly attach a tooth to the surrounding alveolar bone within a gomphosis.

Syndesmoses

Amphiarthrotic fibrous joints where articulating bones are joined by a long membrane or ligament (interosseous membrane) composed of dense regular connective tissue; found between the radius and ulna, and tibia and fibula.

Synchondroses

Cartilaginous joints where bones are united by hyaline cartilage, permitting essentially no motion (synarthroses); examples include epiphyseal plates, costochondral joints, and the first sternocostal joint.

Symphyses

Cartilaginous joints where bones are united through a tough fibrocartilage pad, functioning as amphiarthroses; examples include intervertebral joints and the pubic symphysis.

Articular capsule

A two-layered structure surrounding the joint cavity of a synovial joint, consisting of an outer fibrous layer and an inner synovial membrane.

Fibrous outer layer

The outer layer of the articular capsule composed of dense irregular connective tissue (DICT) that keeps articulating bones from being pulled apart.

Synovial membrane

The inner layer of the articular capsule composed of loose connective tissue that secretes synovial fluid, helps obtain nutrients and $O_2$, and eliminates waste.

Synovial fluid

A fluid secreted by the synovial membrane that provides lubrication (reducing friction), performs metabolic functions (supplying nutrients and removing waste), and provides shock absorption (evenly distributing force).

Articular cartilage

A smooth layer of hyaline cartilage covering the articulating surfaces of bones in a synovial joint; it is avascular and depends on the circulation of synovial fluid for oxygen and nutrients.

Intrinsic ligaments

Thickened bands of dense regular collagenous connective tissue found within the articular capsule of a synovial joint.

Extrinsic ligaments

Ligaments that are not part of the articular capsule and may be located inside or outside the joint cavity.

Tendons

Dense regular collagenous connective tissue cords that connect muscle to bone, pulling on bones during muscle contraction and stabilizing joints via muscle tone.

Bursae

Synovial fluid-filled structures resembling limp water balloons that minimize friction between moving parts of a synovial joint; may be attached to the articular capsule or separate.

Tendon sheaths

Elongated, tubular bursae that surround and protect long tendons passing through high-stress regions.

Arthritis

Inflammation of one or more joints resulting in pain, stiffness, decreased range of motion, and breakdown of articular cartilage.

Osteoarthritis

The most common form of arthritis caused by 'wear and tear', injuries, and advanced age, leading to pain, stiffness, and decreased mobility in joints such as the back, hands, knees, and shoulders.

Rheumatoid arthritis

An autoimmune disease commonly presenting between ages 30 and 50 in which the immune system fails to recognize self-tissue and attacks the synovial joints, destroying articular cartilage.

Gouty arthritis

A form of arthritis in which excess uric acid crystallizes and precipitates into deposits within the connective tissue surrounding a joint.

Nonaxial joints

Synovial joints that allow motion to occur in one or more planes but do not move around a specific axis.

Uniaxial joints

Synovial joints that allow motion around only one single axis.

Biaxial joints

Synovial joints that allow motion to occur around two axes.

Multiaxial joints

Synovial joints (also called triaxial joints) that allow motion to occur around three axes.

Gliding movements

A nonaxial sliding motion between articulating surfaces, characteristic of intercarpal and intertarsal joints.

Flexion

An angular movement that decreases the angle between articulating bones by bringing the bones closer together (e.g., pulling the forearm toward the arm at the elbow).

Extension

An angular movement that increases the angle between articulating bones, moving them farther apart.

Hyperextension

Extension of a joint beyond its anatomical position (e.g., when hyperextending the shoulder while pitching a softball).

Abduction

An angular movement of a body part away from the midline of the body (e.g., the first movement of jumping jacks).

Adduction

An angular movement of a body part toward the midline of the body (e.g., the returning movement of jumping jacks).

Circumduction

A movement in which a freely moveable distal bone moves around a stationary proximal bone in a cone-shaped circular motion.

Rotation

A nonangular pivoting movement in which a bone turns around its own longitudinal axis (medial/internal or lateral/external), such as shaking the head 'no'.

Opposition

A special movement occurring only at the thumb ($1^{\text{st}}$ carpometacarpal joint) that moves the thumb across the palmar surface toward the other digits.

Reposition

A special movement returning the thumb from opposition back to its anatomical position.

Depression

An inferior special movement pulling a body part downward (e.g., opening the mouth).

Elevation

A superior special movement pulling a body part upward (e.g., shrugging the shoulders or closing the mouth).

Protraction

A special movement that moves a body part in an anterior direction.

Retraction

A special movement that moves a body part in a posterior direction.

Inversion

A special movement of the foot that rotates the plantar surface medially toward the midline.

Eversion

A special movement of the foot that rotates the plantar surface laterally away from the midline.

Dorsiflexion

A special movement of the foot in which the toes are pulled upward toward the head.

Plantar flexion

A special movement of the foot in which the toes point downward toward the ground ('tip toes').

Supination

A movement of the forearm where the palm faces anteriorly with the thumb pointing laterally.

Pronation

A movement of the forearm where the palmar surface faces posteriorly with the thumb pointing toward the body.

Plane joint

The simplest and least mobile type of synovial joint; a nonaxial joint that allows only gliding motions between flat surfaces (e.g., intertarsal and intercarpal joints).

Hinge joint

A uniaxial synovial joint in which the convex surface of one bone fits into a concave depression of another bone (e.g., elbow, knee, and interphalangeal joints).

Pivot joint

A uniaxial synovial joint in which the rounded surface of one bone fits into a groove of another bone (e.g., the atlantoaxial joint between atlas and axis).

Condylar joint

A biaxial synovial joint (also called an ellipsoid joint) where an oval, convex surface fits into a shallow concave surface of another bone, permitting flexion/extension and abduction/adduction (e.g., metacarpophalangeal joints).

Saddle joint

A biaxial synovial joint where articulating bone ends each have both convex and concave surfaces that complement each other, allowing greater motion than condylar joints (e.g., carpometacarpal joint of the thumb).

Ball-and-socket joint

A multiaxial synovial joint where the spherical surface of one bone fits into a cup or socket of another bone, allowing movement in all axes (e.g., shoulder and hip joints).