JOINTS Every bone except the hyoid forms a joint (articulation) ◦2 functions  Hold bones together securely  Give the rigid skeleton mobility 2 CLASSIFICATIONS ◦Functional ◦Structural

◦Functional  Synarthroses (immovable joints)  Amphiarthroses (slightly moveable)  Diarthroses (freely moveable) ◦ Allow mobility ◦Structural  Fibrous – generally immovable  example = sutures of skull found where firm attachments and protection of internal organs are priorities

◦Structural  Fibrous – generally immovable  example = sutures of skull  Syndesmoses- longer fibers than sutures, joint has more give ◦ Ex-distal ends of tibia and fibula

Cartilaginous – mostly amphiarthrotic; bone ends connected by cartilage –Ex. pubic symphysis, intervertebral joints –Epiphesial plates of growing long bones, joints between 1 st ribs and sternum-immoveable cartilage joints

 Synovial – freely moveable; articulating ends are separated by a joint cavity containing synovial fluid ◦ 4 distinguishing features  Articular cartilage -covers ends of bones forming the joint  Fibrous articular capsule -encloses joint surfaces; capsule is lined by synovial membrane  Joint cavity- enclosed by articular capsule; contains lubricating synovial fluid  Fibrous capsule is usually reinforced with ligaments; fluid-filled sacs called bursae cushion tendons where they cross the bone  See fig 5.28 p. 149

◦ Types of synovial joints  Plane-nonaxial, flat, short slipping or gliding motion, found in carpals-no rotation  Hinge- uniaxial-elbow, ankle, philanges  Pivot- uniaxial, pivot joint between radius and ulna  Condyloid-biaxial, side to side, back and forth, ex. metacarpal and phalanges  Saddle-biaxial, both articular surfaces are saddle shaped. Ex. twiddle thumbs  Ball and socket-multiaxial-shoulder and hip

◦Dislocation = when a bone is forced out of its normal position in the joint cavity

Inflammatory disorders of joints ◦Bursitis = inflammation of bursae or synovial membrane ◦Sprains = ligaments or tendons reinforcing a joint are damaged by excessive stretching, or they are torn away from the bone  Heal slowly – tendons/ligaments have poor blood supply  Also very painful

◦Arthritis = over 100 different inflammatory or degenerative diseases that damage the joints  The most widespread, crippling disease in the US (1 out of 7)  Initial symptoms = pain, stiffness, and swelling of the joint ◦ may be followed by changes in joint structure fig  Acute forms = result from bacterial invasion and are treated w/antibiotics

 Chronic forms ◦ Osteoarthritis  Most common  Degenerative condition  Affects the aged  Softening, fraying and breakdown of cartilage leave bones exposed  Extra bone tissue (bone spurs) grow around margins of eroded cartilage  Restricts joint movement; movement results in a crunching noise  Commonly affects fingers, cervical and lumbar joints, knees and hips  Course is slow and irreversible but rarely crippling  Controlled with analgesics such as aspirin and rest when painful

◦ Rheumatoid  Onset usually between 30 and 40  Affect 3 X more women than men  Affects fingers, wrists, ankles and feet at same time  Course is marked by remissions and flare-ups  An autoimmune disease – body’s immune system attempts to destroy its own tissue  Triggers are unknown  Cartilage destroyed; scar tissue ossifies so that bone ends are permanently fused  Treatment = large doses of anti-inflammatory drugs; exercise to reduce stiffness

◦ Gouty arthritis  Uric acid (metabolic waste) accumulates in blood and is deposited as crystals in joints  Painful attack of a single joint  More common in males  Tends to run in families  Treatment = avoid foods high in nucleic acids, alcohol and excessive vitamin C