Human Anatomy and Physiology Chapter 9 Part A: Joints

Comprehensive vocabulary flashcards covering the structural and functional classification of joints, structural anatomy of fibrous, cartilaginous, and synovial joints, joint dynamics, stability factors, and specific synovial joint movements.

Joints (Articulations)

Sites where two or more bones meet, serving to give the skeleton mobility and hold it together.

Synarthroses

Immovable joints based on the functional classification of joint movement.

Amphiarthroses

Slightly movable joints based on the functional classification of joint movement.

Diarthroses

Freely movable joints based on the functional classification of joint movement, including almost all limb joints.

Fibrous joints

Joints where articulating bones are joined by dense fibrous connective tissue without a joint cavity; most are immovable.

Sutures

Rigid, interlocking fibrous joints found only in the skull that contain short connective tissue fibers allowing for expansion during youth.

Synostoses

Closed, completely ossified and fused sutures that transform into immovable bony junctions during middle age.

Syndesmoses

Fibrous joints where bones are connected exclusively by ligaments or bands of fibrous tissue; movement varies from immovable to freely movable depending on fiber length.

Gomphoses

Peg-in-socket fibrous joints; the only examples in the human body are teeth anchored into alveolar sockets.

Periodontal ligament

The fibrous connective tissue band that secures a tooth within its alveolar socket in a gomphosis joint.

Cartilaginous joints

Joints in which articulating bones are united by cartilage and lack a joint cavity; not highly movable.

Synchondroses

Cartilaginous joints where a bar or plate of hyaline cartilage unites the bones; virtually all are immovable (synarthrotic).

Symphyses

Strong, slightly movable (amphiarthrotic) cartilaginous joints where articulating bones are united by a compressible fibrocartilage pad.

Synovial joints

Freely movable (diarthrotic) joints in which articulating bone ends are separated by a fluid-filled joint cavity.

Articular cartilage

Glassy-smooth hyaline cartilage covering opposing bone surfaces at a synovial joint that absorbs compression and prevents bone crushing.

Joint (synovial) cavity

A potential space unique to synovial joints that contains a small amount of slippery synovial fluid.

Articular (joint) capsule

A two-layered sleeve enclosing the joint cavity, composed of an external fibrous layer of dense irregular connective tissue and an inner synovial membrane of loose connective tissue.

Synovial membrane

The inner loose connective tissue layer of the articular capsule that produces and secretes synovial fluid.

Synovial fluid

A viscous, slippery filtrate of plasma and hyaluronic acid that lubricates joint surfaces, nourishes articular cartilage, and contains phagocytic cells.

Articular discs (Menisci)

Pads of fibrocartilage extending inward from the articular capsule to divide the cavity, improve fit between articulating bone ends, and reduce wear.

Bursae

Flattened fibrous sacs lined with synovial membrane and filled with synovial fluid that act as lubricating bearings to reduce friction between adjacent moving structures.

Tendon sheaths

Elongated, fluid-filled bursae that wrap completely around tendons subjected to friction.

Muscle tone

Low levels of contractile activity in resting muscles that keep tendons taut across joints; the most important factor in stabilizing synovial joints.

Origin

The skeletal site of attachment of a muscle to the immovable (or less movable) bone.

Insertion

The skeletal site of attachment of a muscle to the movable bone, which moves toward the origin during muscle contraction.

Nonaxial movement

Joint motion limited to slipping or gliding movements because it does not occur around a specific axis.

Uniaxial movement

Joint motion that is restricted to movement in or around one single plane.

Biaxial movement

Joint motion that occurs in or around two perpendicular planes.

Multiaxial movement

Joint motion occurring in or around all three planes of space and all three axes.

Gliding movements

Simple motions where flat bone surfaces slide across each other, as seen between intercarpal and intertarsal bones.

Flexion

An angular movement, usually in the sagittal plane, that decreases the angle between two articulating bones.

Extension

An angular movement, usually in the sagittal plane, that increases the angle between two articulating bones.

Hyperextension

An angular movement that extends an articulating joint beyond its normal anatomical position.

Abduction

Movement of a limb away from the midline of the body along the frontal plane.

Adduction

Movement of a limb toward the midline of the body along the frontal plane.

Circumduction

A composite angular movement combining flexion, abduction, extension, and adduction such that the distal end of a limb describes a cone in space.

Rotation

The turning of a bone around its own longitudinal axis, directed either toward the midline (medial) or away from it (lateral).

Supination

Rotation of the forearm such that the palm faces anteriorly and the radius and ulna lie parallel to each other.

Pronation

Rotation of the forearm where the radius crosses over the ulna to face the palm posteriorly.

Dorsiflexion

Lifting the foot so that its superior surface approaches the shin.

Plantar flexion

Depressing the foot to point the toes downward.

Inversion

A special medial movement of the foot that turns the sole inward toward the midline.

Eversion

A special lateral movement of the foot that turns the sole outward away from the midline.

Protraction

A nonangular anterior movement in a transverse plane, such as jutting the mandible outward.

Retraction

A posterior movement that pulls a protracted body part back toward the body, such as pulling the mandible back toward the neck.

Elevation

Lifting a body part superiorly along a frontal plane, such as closing the jaw or shrugging the shoulders.

Depression

Moving an elevated body part inferiorly, such as opening the jaw.

Opposition

A special action allowed by the saddle joint of carpometacarpal joint I enabling the thumb to touch the tips of other digits on the same hand.

Plane joint

A synovial joint with flat articulating surfaces that permits nonaxial gliding movements.

Hinge joint

A uniaxial synovial joint in which a cylindrical bone projection fits into a trough-shaped surface to allow flexion and extension.

Pivot joint

A uniaxial synovial joint in which the rounded end of one bone rotates within a sleeve composed of bone and ligament.

Condylar joint

A biaxial synovial joint featuring oval convex and concave surfaces that permits angular movements across two planes.

Saddle joint

A biaxial synovial joint where both articulating bone surfaces have complementary concave and convex regions, such as the carpometacarpal joint of digit I.

Ball-and-socket joint

A multiaxial synovial joint where a spherical head articulates with a cup-like socket, offering the greatest freedom of movement including rotation.