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Gomphoses

(gomphosis)a peg-in-socket fibrous joint (ex: articulation of a tooth with its bony alveolar socket), Fibrous connection is the periodontal ligament • Peg-in-socket joints of teeth in alveolar sockets •Fibrous connection is the periodontal ligament

Synovial Joints: Six Distinguishing Features

1. Articular cartilage: hyaline cartilage - Prevents crushing of bone ends 2. Joint (synovial) cavity --Small, fluid-filled potential space 3. Articular (joint) capsule - Two layers • External Fibrous layer - Dense irregular connective tissue • Inner Synovial membrane - Loose connective tissue --Makes synovial fluid 4. Synovial fluid - Viscous, slippery filtrate of plasma and hyaluronic acid - Lubricates and nourishes articular cartilage --Contains phagocytic cells to remove microbes and debris 5. Different types of reinforcing ligaments - Capsular • Thickened part of fibrous layer - Extracapsular • Outside the capsule --Intracapsular •Deep to capsule; covered by synovial membrane 6. Nerves and blood vessels - Nerve fibers detect pain, monitor joint position and stretch --Capillary beds supply filtrate for synovial fluid

Three General Types of Movements of Synovial Joints

1. Gliding 2. Angular movements - Flexion, extension, hyperextension - Abduction, adduction (toward midline) - Circumduction 3. Rotation --Medial and lateral rotation

Fibrous joints

An articulation in which the bones are joined together by dense fibrous connective tissue, lack a joint cavity, and almost no motion is possible. Types are sutures, syndemoses, and gomphoses. (Most are synarthrotic joints.)

Structural Classification of Joints •

Based on - Material binding bones together - Presence/absence of joint cavity • Three structural classifications: - Fibrous joints - Cartilaginous joints --Synovial joints

Synovial Joints •

Bones separated by fluid-filled joint cavity • All are diarthrotic •Include ~ all limb joints; most joints of body

- Amphiarthroses

Cartilaginous joints, that are slightly movable and found at the symphysis pubis

Cartilaginous joints

Have no joint cavity, Bones held together by cartilage. Examples are growth plates, disks between vertebrae and the pelvic symphysis

Syndesmoses

Joint where two bones are bound along their length by a ligament (interosseus membrane). Most movable of fibrous joints. • Bones connected by ligaments (bands of fibrous tissue) • Fiber length varies so movement varies, i.e., - Little to no movement at inferior tibiofibular joint --Large amount of movement at interosseous membrane connecting radius and ulna

- Synarthroses

fibrous joints, that are immovable and found in the sutures of skull

Diarthroses

freely movable joints, predominate in the limbs (ex: synivial joints)

Sutures

immovable joints that unite cranial bones Fibrous Joints: Sutures • Rigid, interlocking joints • Immovable joints for protection of brain • Contain short connective tissue fibers • Allow for growth during youth • In middle age, sutures ossify and fuse --Called Synostoses

Synovial joints

joints that are held together by a joint capsule and ligaments and are most associated with movement in the body, bone ends separated by joint cavity w/synovial fluid; i.e knee

Arthritis

• >100 different types of inflammatory or degenerative diseases that damage joints • Most widespread crippling disease in the U.S. • Symptoms: pain, stiffness, and swelling of joint • Acute forms: caused by bacteria, treated with antibiotics •Chronic forms: osteoarthritis, rheumatoid arthritis, and gouty arthritis Osteoarthritis (OA) • Common, irreversible, degenerative (''wear-and-tear'') arthritis • May reflect excessive release of enzymes that break down articular cartilage • By age 85 half of Americans develop OA, more women than men •Probably related to normal aging process Rheumatoid Arthritis • Chronic, inflammatory, autoimmune disease of unknown cause - Immune system attacks own cells • Usually arises between ages 40 and 50, but may occur at any age; affects 3 times as many women as men •Signs and symptoms include joint pain and swelling (usually bilateral), anemia, osteoporosis, muscle weakness, and cardiovascular problems • RA begins with synovitis of the affected joint - Inflammatory blood cells migrate to joint, release inflammatory chemicals that destroy tissues - Synovial fluid accumulates → joint swelling and inflamed synovial membrane which thickens --Erosion of cartilage, scar tissue forms and connects articulating bone ends (ankylosis) Gouty Arthritis • Deposition of uric acid crystals in joints and soft tissues, followed by inflammation • More common in men • Typically affects joint at base of great toe • In untreated gouty arthritis, bone ends fuse and immobilize joint •Treatment: drugs, plenty of water, avoidance of alcohol

Synovial Joints: Movements Allowed

• All muscles attach to bone or connective tissue at no fewer than two points - Origin—attachment to immovable bone - Insertion—attachment to movable bone • Muscle contraction causes insertion to move toward origin --Movements occur along transverse, frontal, or sagittal planes Synovial Joints: Range of Motion (ROM) • Nonaxial—slipping movements only • Uniaxial—movement in one plane • Biaxial—movement in two planes •Multiaxial—movement in or around all three planes

Elbow Joint

• Articulation of radius and ulna with humerus • Hinge joint - Primarily trochlear notch of ulna with trochlea of humerus --Flexion and extension only

Shoulder (Glenohumeral) Joint

• Ball-and-socket joint - Head of humerus with glenoid cavity of scapula • Most freely moving joint in body --Stability sacrificed

Hip (Coxal) Joint

• Ball-and-socket joint • Head of the femur articulates with acetabulum • Good range of motion, but limited by the deep socket - Rim of fibrocartilage - Acetabular labrum •Enhances depth of socket so hip dislocations rare

Cartilaginous Joints: Synchondroses

• Bar/plate of hyaline cartilage unites bones e.g., - Temporary epiphyseal plate joints • Become synostoses after plate closure - Cartilage of 1st rib with manubrium • ~ All are synarthrotic

• Three functional classifications of joints -

• Based on - Amount of movement joint allows Synarthroses—immovable joints - Amphiarthroses—slightly movable joints --Diarthroses—freely movable joints

Cartilaginous Joints

• Bones united by cartilage • No joint cavity • Not highly movable • Two types: - Synchondroses -Symphyses

Inflammatory and Degenerative Conditions

• Bursitis - Inflammation of bursa, usually caused by blow or friction - Treated with rest and ice and, if severe, anti-inflammatory drugs • Tendonitis - Inflammation of tendon sheaths typically caused by overuse --Symptoms and treatment similar to bursitis

Developmental Aspect of Joints

• By embryonic week 8, synovial joints resemble adult joints • Joint's size, shape, and flexibility modified by use • Advancing years take toll on joints - Ligaments and tendons shorten and weaken - Intervertebral discs more likely to herniate - Most people in 70s have some degree of OA •Full-range-of-motion exercise key to postponing joint problems

Common Joint Injuries

• Cartilage tears - Due to compression and shear stress - Fragments may cause joint to lock or bind - Cartilage rarely repairs itself - Repaired with arthroscopic surgery • Ligaments repaired, cartilage fragments removed with minimal tissue damage or scarring - Partial menisci removal renders joint less stable but still mobile; complete removal leads to osteoarthritis - Meniscal transplant in younger patients --Perhaps meniscus grown from own stem cells in future • Sprains - Reinforcing ligaments stretched or torn - Partial tears slowly repair heal • Poor vascularization - Three options if torn completely • Ends sewn together • Replaced with grafts •Time and immobilization • Dislocations (luxations) - Bones forced out of alignment - Accompanied by sprains, inflammation, and difficulty moving joint - Caused by serious falls or contact sports - Must be reduced to treat •Subluxation—partial dislocation of a joint

Cartilaginous Joints: Symphyses

• Fibrocartilage unites bone - Hyaline cartilage present as articular cartilage •Strong, flexible amphiarthroses

Angular Movements

• Increase or decrease angle between two bones • Movement along sagittal plane - Flexion—decreases the angle of the joint - Extension—increases the angle of the joint •Hyperextension—movement beyond the anatomical position • Movement along frontal plane - Abduction—movement away from the midline - Adduction—movement toward the midline • Circumduction - Involves flexion, abduction, extension, and adduction of limb --Limb describes cone in space

Knee Joint

• Largest, most complex joint of body • Three joints surrounded by a single joint cavity - Femoropatellar joint • Plane joint • Allows gliding motion during knee flexion - Lateral and medial tibiofemoral joints • Femoral condyles with lateral and medial menisci of tibia •Allow flexion, extension, and some rotation when knee partly flexed Ligaments Stabilizing Knee Joint • Capsular and extracapsular ligaments - Help prevent hyperextension of knee - Fibular and tibial collateral ligaments - Oblique popliteal ligament --Arcuate popliteal ligament

Temporomandibular Joint

• Mandibular condyle articulates with temporal bone • Two types of movement - Hinge—depression and elevation of mandible - Gliding—e.g., side-to-side (lateral excursion) grinding of teeth •Most easily dislocated joint in the body

Gliding Movements

• One flat bone surface glides or slips over another similar surface • Examples: - Intercarpal joints (waving hand) - Intertarsal joints --Between articular processes of vertebrae

Three Stabilizing Factors at Synovial Joints

• Shapes of articular surfaces (minor role) • Ligament number and location (limited role) • Muscle tendons that cross joint (most important) - Muscle tone keeps tendons taut --Extremely important in reinforcing shoulder and knee joints and arches of the foot

Types of Synovial Joints******

• Six types, based on shape of articular surfaces: - Plane—gliding carpals - Hinge----elbow, crunching fingers (not knee)--uniaxial - Pivot---radius - Condylar—biaxial movement, knuckles - Saddle---thumb, biaxial --Ball-and-socket---multiaxial, x/y/z planes

Special Movements at Synovial Joints

• Supination and pronation of radius and ulna • Dorsiflexion and plantar flexion of foot • Inversion and eversion of foot • Protraction and retraction • Elevation and depression of mandible •Opposition of thumb of mandible

three types of fibrous joints

• Three types: - Sutures - Syndesmoses --Gomphoses

Rotation

• Turning of bone around its own long axis - Toward midline or away from it - Medial and lateral rotation • Examples: - Between C1 and C2 vertebrae --Rotation of humerus and femur