Anatomy & Physiology The Skeletal System- Part 4

JOINTS  aka Articulations  2 Functions: 1. Hold Bones Together 2. Allows otherwise rigid skeleton to have some flexibility

Classification of Joints  Functionally  Named according to how much movement joint  Structurally  Named according to presence of fibrous tissue, cartilage, or a joint cavity separate the articulated bones

Functional Joints  Synarthrosis  Immovable joints  Skull bones  Amphiarthrosis  Slightly movable joints  Symphysis pubis  Diarthrosis  Freely movable joints  Ball & Socket or Hinge Joints

Structural Joints 1. Fibrous Joints Bones united by fibrous tissue Joint connecting distal tibia & fibula 2. Cartilaginous Joints Bone ends connected by cartilage Pubic symphysis 3. Synovial Joints Articulating ends of bone separated by joint cavity

4 Features of Synovial Joints 1. Articular Cartilage Hyaline cartilage covers ends of bones 2. Fibrous Articular Capsule Joint surfaces enclosed by capsule of fibrous CT Capsule lined by synovial membrane 3. Joint Cavity Contains synovial fluid 4. Reinforcing Ligaments Reinforce fibrous articular capsule

Types of Synovial Joints 1. PLANE JOINT Articular surfaces flat Allow gliding movement (w/out rotation) Example: intercarpal joints of wrist & ankle

Types of Synovial Joints 2. HINGE JOINT  cylindrical end of bone fits into trough-shaped surface of another bone  Angular movement allowed in 1 plane  Examples: elbow, knee, interphalangeal joints

Types of Synovial Joints 3. PIVOT JOINT  Rounded end of 1 bone fits into sleeve or ring of another bone  allows 1 bone to rotate along its long axis  Example: joint between atlas & dens of axis

Types of Synovial Joints 4.CONDYLOID JOINT  “knuckle-like”  Egg-shaped end of 1 bone fits into oval concavity in another bone  Allows for moving bone to travel side-to-side & back-and-forth but cannot rotate along its long axis  Example: metacarpophalangeal joint

4. CONDYLOID JOINT

Types of Synovial Joints 5. SADDLE JOINTS  Each articular surface has convex & concave areas  Same movements as condyloid joints  Example: twiddling your thumbs

Types of Synovial Joints 6. BALL & SOCKET JOINTS  Spherical head of 1 bone fits into a round socket formed by 1 or more bones  Allows movement is 3 dimensions(most freely moving of synovial joints)

SPRAINS  Ligaments or tendons reinforcing a joint are damaged by excessive stretching or tearing  Both have poor blood supply so heal slowly

ARTHRITIS  “inflammation of a joint”  General term for >100 different diseases  Most wide-spread, disabling disease in USA  Onset: same symptoms: joint stiffness & swelling  Synovial membrane inflammed  thickens  less synovial fluid  increased friction

Rheumatoid Arthritis  Autoimmune disorder  Adult onset or Juvenile onset  Women 3x more often than men  Any synovial joint could be affected, often symmetrical involvement  disfiguring

Rheumatoid Arthritis

Osteoarthritis  Most common form of arthritis  Chronic degenerative condition: “wear-and- tear”  Affects articular cartilage (eventually breaks down)  increased friction  bone spurs develop  restricts movement

Osteoarthritis