AppendicularSkeleton

The Joints

The Joints

• Joints serve to hold the bones together but allow movement at the same time

• Joints are classified by structure and function– Structural refers to tissues found in the joint

• Fibrous• Cartilaginous• Synovial

– Functional refers to the amount of movement allowed• Synarthroses – no movement allowed• Amphiarthroses – slightly movable• Diarthroses – freely movable

The Joints

• Fibrous Joints– Fibrous tissue connects bones together at site of

articulation– Usually associated with immovable, or

synarthroses, joints (ex. the sutures of the skull)

• Cartilaginous Joints– Joints that include bones separated by cartilage

tissue– Usually amphiarthrotic (ex. intervertebral joints) or

synarthrotic (ex. epiphyseal plates)

The Joints

The Joints

• Synovial Joints– Will include cartilage, but also have a joint cavity

between bone ends– All synovial joints have four features:

• Articular cartilage – covers the ends of bones• Fibrous articular capsule – joint surfaces enclosed

by capsule of fibrous connective tissue that is lined by a synovial membrane

• Joint cavity – the area enclosed by the capsule, contains synovial fluid

• Reinforcing ligaments – capsule is reinforced/held in place by ligaments

The Joints

The Joints

• Movement of synovial joints is determined by their shape– Plane Joint – articular surfaces are flat and allow

minimal slipping or gliding movement (ex. intercarpal joints)

– Hinge Joint – cylindrical shape of one end with the other end fitting around it allows the bones to only move around one axis (ex. elbow, between phalanges)

– Pivot Joint – round end fits into a complimentary end of another bone, only moves around one axis (ex. radioulnar joint)

The Joints

– Condyloid Joint – slightly rounded end fits into a shallow concavity of articulating bone, allows movement from side to side and back and forth, but no rotation (ex. knuckles)

– Saddle Joint – each surface has a convex and concave area resembling a saddle, allows exaggerated condyloid movement (ex. #1 metacarpal and carpal joint)

– Ball-and-socket Joint – rounded head of one bone fits into the socket of the other bone, allows side to side, back and forth, and rotation movements (ex. shoulder and hip)

The Joints