Chapter 8 Joints of the Skeletal System Articulations Functional junctions between bones Bind parts of skeletal system together Make bone growth possible Permit parts of the skeleton to change shape during childbirth Enable body to move in response to skeletal muscle contraction

Classification of Joints Fibrous Joints dense connective tissues connect bones between bones in close contact synarthrotic immovable amphiarthrotic slightly movable diarthrotic freely movable Cartilaginous Joints hyaline cartilage or fibrocartilage connect bones Synovial Joints most complex allow free movement held together by a fluid filled joint cavity

Fibrous Joints 3 Types Syndesmosis Suture Gomphosis Syndesmosis a sheet or bundle of fibrous tissue connects bones amphiarthrotic lies between tibia and fibula

Fibrous Joints Suture between flat bones synarthrotic thin layer of connective tissue connects bones Gomphosis cone-shaped bony process in a socket tooth in jawbone synarthrotic

Cartilaginous Joints 2 Types Synchondrosis Symphysis Synchondrosis bands of hyaline cartilage unite bones epiphyseal plate (temporary) between manubrium and first rib synarthrotic

Cartilaginous Joints Symphysis pad of fibrocartilage between bones pubis symphysis joint between bodies of adjacent vertebrae amphiarthrotic

Synovial Joints diarthrotic joint cavity synovial fluid joint capsule synovial membrane bursae

General structure of a synovial joint Articular cartilage covers ends of bones Spongy bone usually beneath cartilage Subchondral plate between bone and cartilage that absorbs shock Joint capsule strengthened by ligaments that hold bones together Synovial membranes secretes a clear viscous synovial fluid

Synovial fluid moistens, provides nutrients, and lubricates articular surfaces Some areas have villi to increase surface area Menisci divide some synovial joints into compartments Some joints have fluid filled bursae Bursae are usually located between the skin and underlying bony prominances

Bursae cushion and aid movement of tendons over bony parts Bursae are named according to their locations

Types of Synovial Joints Ball-and-Socket Joint hip shoulder Widest range of motion Condyloid Joint between metacarpals and phalanges Wide range of movement but not rotation

Types of Synovial Joints Gliding Joint (Plane) between carpals between tarsals Permits sliding and twisting Hinge Joint elbow between phalanges Moves in one plane only

Types of Synovial Joints Pivot Joint between proximal ends of radius and ulna Permits rotation Saddle Joint between carpal and metacarpal of thumb Permits variety of movement

Types of Joint Movements abduction/adduction dorsiflexion/plantarflexion flexion/extension/hyperextension

Types of Joint Movements rotation/circumduction supination/pronation

Types of Joint Movements eversion/inversion protraction/retraction elevation/depression

Shoulder Joint ball-and-socket head of humerus glenoid cavity of scapula loose joint capsule bursae ligaments prevent displacement very wide range of movement

Shoulder Joint

Elbow Joint hinge joint gliding joint flexion and extension trochlea of humerus trochlear notch of ulna gliding joint capitulum of humerus head of radius flexion and extension many reinforcing ligaments stable joint

Elbow Joint

Hip Joint ball-and-socket joint head of femur acetabulum of coxa heavy joint capsule many reinforcing ligaments less freedom of movement than shoulder joint

Hip Joint

Knee Joint largest joint – most complex medial and lateral condyles of distal end of femur medial and lateral condyles of proximal end of tibia femur articulates anteriorly with patella modified hinge joint (2 condyloids & gliding) flexion/extension/little rotation strengthened by many ligaments and tendons menisci separate femur and tibia bursae

Knee Joint

Life-Span Changes Joint stiffness is an early sign of aging Fibrous joints first to change; can strengthen over a lifetime Changes in symphysis joints of vertebral column diminish flexibility and decrease height Synovial joints lose elasticity Disuse hampers the blood supply Activity and exercise can keep joints functional longer

Clinical Application Joint Disorders Sprains damage to cartilage, ligaments, or tendons associated with joints forceful twisting of joint overstretching Bursitis inflammation of a bursa overuse of a joint

Arthritis inflamed, swollen, painful joints Rheumatoid Arthritis autoimmune disorder synovial membrane thickens forming a mass called a pannus articular cartilage is damaged and bones may fuse together (bony ankylosis) systemic disorder often affecting the skin, eyes, lungs, blood vessels, and heart

Osteoarthritis Most common type Degenerative and usually occurs with aging Articular cartilage softens and disintegrates slowly Joints become painful with restricted movements

Lyme Arthritis Bacterial infection passed in a tick bite Causes intermittent arthritis of several joints several weeks after initial infection Symptoms first appear as a rash, fatigue, flulike aches and pains Treated with antibiotics May be difficult to diagnose

Normal hand

Bony Ankylosis of the hand

Osteoarthritis – most common type articular cartilage wears away placing stress on the subchondral plate degenerative disorder caused by aging If a joint is immobilized for a long period of time the articular cartilage may soften and degenerate Arthroscopy is used to examine a joint – blue box page 271