Articulation and Joints ( Chapter 9)

Mobility

How much a joint can move.

Stability

How strong and secure a joint is.

Inverse Relationship between Mobility and Stability

The more mobile a joint is, the less stable it tends to be; conversely, the more stable a joint is, the less mobility it usually has.

Fibrous Joints

Joints held together by dense regular connective tissue; allow little or no movement. Examples: Sutures of the skull, teeth in sockets.

Cartilaginous Joints

Bones joined by cartilage; allow limited movement and provide support. Examples: Intervertebral discs, pubic symphysis.

Synovial Joints

Joints with a fluid-filled cavity allowing for the most movement; examples include shoulder, hip, elbow.

Synarthrosis

Immovable joints. Examples: Sutures of the skull.

Amphiarthrosis

Slightly movable joints. Examples: Pubic symphysis, intervertebral discs.

Diarthrosis

Freely movable joints, including all synovial joints. Examples: Shoulder, hip, knee.

Articular Capsule

• – Surrounds the 2 ends of the bones that articulate, forming a tight space filled with synovial fluid. The capsule has an outer fibrous layer for strength and an inner synovial membrane that produces synovial fluid.

Joint Cavity

Space within the capsule filled with synovial fluid that allows for free movement.

Synovial Fluid

Thick fluid that lubricates the joint, reduces friction, absorbs shock, and nourishes cartilage.

Articular Cartilage

Smooth cartilage covering the ends of bones to reduce friction and protect from wear. Made of smooth hyaline cartilage.

Ligaments

Connective tissues that connect bone to bone, providing stability and strength.

Bursae

• Fibrous, saclike structures that contain synovial fluid and are lined by a synovial membrane. They act like cushions or fat pads that fill spaces when bones move and the joint cavity changes shape. Often scattered around the periphery of a joint and function as packing material while providing protection and reducing friction between bones, tendons, and muscles.

Tendons

• Attach muscles to bones and help stabilize joints. Tendons also assist with movement by transmitting the force of muscle contraction to the bone.

Planar (Gliding) Joints

Uniaxial joints allowing small sliding movements; example: Wrist joints.

Hinge Joints

Uniaxial joints allowing movement in one direction; example: Elbow.

Pivot Joints

Uniaxial joints allowing rotational movement; example: Atlas and dens (C1–C2 vertebrae).

Condyloid (Ellipsoid) Joints

Biaxial joints allowing movement in two planes; example: Fingers (metacarpophalangeal joints).

Saddle Joints

Biaxial joints with greater flexibility; example: Thumb joint.

Ball-and-Socket Joints

Multiaxial joints allowing movement in all directions; example: Hips and shoulders.

Uniaxial Joints

Joints where bones move in one plane; examples: Hinge joints (elbow), Pivot joints (atlas-axis).

Biaxial Joints

Joints where bones move in two planes; examples: Condyloid joints (knuckles), Saddle joints (thumb).

Multiaxial Joints

Joints allowing movement in multiple planes; example: Ball-and-socket joints (hips and shoulders).

Flexion

Decreasing the angle of the joint; bending the joint.

Extension

Increasing the angle of the joint; straightening the joint.

Dorsiflexion

Decreasing the angle of the ankle joint.

Plantarflexion

Increasing the angle of the ankle joint.

Elevation

Moving a body part in a superior position.

Depression

Moving a body part in an inferior position.

Eversion

Rotating the ankle so that the sole points away from the other foot.

Inversion

Rotating the ankle so that the sole points towards the other foot.

Abduction

Moving a limb away from the medial line of the body.

Adduction

Moving a limb towards the medial line of the body.

Lateral Rotation

Rotating a limb away from the center line of the body.

Medial Rotation

Rotating a limb towards the center line of the body.

Pronation

Rotating the forearm so that the palm faces down.

Supination

Rotating the forearm so that the palm faces up.

Retraction

Posterior movement bringing the shoulders back.

Protraction

Anterior movement bringing the shoulders forward.

Lateral Flexion

Bending the spine to the side away from the medial line of the body.

Blood Vessels

• Attach muscles to bones and help stabilize joints. Tendons also assist with movement by transmitting the force of muscle contraction to the bone.