Chapter 8- Joints OR Articulations PDF

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JOINTS OR ARTICULATIONS Joints – connections between 2 or more bones - functions – gives skeleton mobility - hold skeleton together - classification of bones: I. Functional - based on amount of movement: 1. synarthrosis – immovable (ex: sutures) 2. amphiarthrosis – slightly movable (ex: vertebral joints) 3. diarthrosis – freely movable (ex: shoulder, hip joints) II. Structural – based on the material binding together and whether a cavity is present or not 1. Fibrous joints – held together by dense fibrous CT - no joint cavity - mostly synarthrosis (immovable) a. Sutures – rigid interlocking joints with short CT fibers continued with the periosteum. in spite of the interlocking structure, the sutures give way to the expanding brain as it grows. - once completely fused, it is called Synostosis or bony joint. (Example of synostosis is “metopic” suture) b. Syndesmoses - articulating bone are far from each other. the fibrous CT maybe ligament or interosseous membrane - maybe immovable or slightly movable - ex: distal fibulotibial joint (synarthrosis, by ligament) radioulnar joints (amphiarthrosis, by interosseous membrane) c. Gomphosis – a cone shape peg fit into a socket, the CT is periodontal ligament - ex: teeth in the alveolar process (amphiarthrosis) 2. Cartilaginous joints: - connected by cartilage - no joint cavity a. Synchondrosis – a plate of hyaline cartilage joints the bones - a synarthrotic joint - in adult, ossify and become synostosis (immovable) - ex: epiphyseal plate, the cartilage joining the first rib to the manubrium of the sternum b. Symphysis – articular surface covered by hyaline cartilage which fused with the intervening plate, of fibrocartilage (which is compressible and resilient) - strong and flexible (amphiarthrosis) - ex: symphysis pubis, intervertebral joints

3. Synovial joints - articulating bones are separated by cavities - freely movable (diarthrosis) - ex: all limb joints - has articular cartilage – (hyaline cartilage) - reduce friction, absorb shock - has synovial cavity - has articular capsule 2 layers: - outer fibrous layer continuous with periosteum (dense irregular CT) inner synovial membrane (loose CT – areolar with elastic fibers) - has synovial fluid – interstitial fluid filtered from blood plasma - has hyaluronic acid produced by the fibroblast like cells of the SM - has phagocytic cells - functions: for lubrication, prevent friction - nourishment of the articular cartilage - phagocytosis - has reinforcing 3 ligaments: - capsular – the fibrous ligament of the fibrous capsule - extra capsular – ex: fibular or tibial collateral ligaments of knee joints intracapsular – ex: anterior and posterior cruciate ligaments of knee joints - rich of nerves (pain receptors, proprioceptors, pressure receptors ) - rich in blood vessel supply – capillaries that filter the synovial fluid - other features of some synovial joints - fatty pads – serve as cushion between fibrous layer and synovial membrane or bone - meniscus – a fibrocartilage that fits both ends of bones, stabilize joint and reduce wear and tear Friction reducing structures in synovial joints: 1. Burae – flat sac like structure with synovial membrane and synovial fluid (the membrane and fluid are similar to that of the synovial joints) - act as “ball bearing “between - skin and bone - tendon and bone - ligament and bone 2. Tendon sheath – a bursa that wrap around the tendon Note: Tendon / ligament Stabilizing factors in joints:

1. shape of the joints – ball and socket joint of hip is very stable -knee joint is less stable 2. presence of ligaments – the more ligaments the stronger the joint is - ligaments extend only 6% of its length 3. muscle tone – the tendon is kept taut by the muscle tone. - most important stabilizing factor - extremely important in knee joint, shoulder joint and arches of the foot Range of motion in synovial joints - non axial (slipping movement only ) - uniaxial - biaxial - multiaxial

Movement of synovial joints – gliding – one flat bone glides or slip over another flat bone - ex: intercarpal joints intertarsal joints between articular process of vertebrae - angular movements – flexion / extension / hyperextension - abduction / adduction - circumduction - rotation – medial / lateral (between C1 and C2 )

- special movement – supinaton / pronation - dorsiflexion / plantar flexion of the foot - inversion / eversion - protraction / retraction - elevation / depression - opposition Classification of synovial joints: 6 types (based on shape and articular surface) 1. Plane joints – non axial - short gliding movement - flat articular surfaces - ex: gliding joint of trapezium and scaphoid 2. Hinge joints – uniaxial, single plane - extension / flexion movement - ex: elbow joint 3. Pivot joints - a rounded end of one bone conforms to a ring of another bone

- uniaxial - ex: proximal radioulnar joint 4. Condyloid joint –oval shape projection fits into an oval shape depression -biaxial -permit all angular movement - ex: metacarpophalangeal joints from 2nd to 5th digits 5. Saddle joints – just like a person sitting on a saddle - biaxial - circumduction, opposition ex: trapezium and first metacarpals 6. Ball and socket joints – ball fitting in a cup like depression - most freely moving synovial joint - multiaxial - hip joint Selected joints of the body: 1. Knee joint – tibiofemoral joint or patellar joint - largest and most complex joint - made up of 3 joints – femoropatellar joint (a planar joint ) - lateral condyle of femur with lateral meniscus of the tibia - medial condyle of femur with medial meniscus of the tibia -the last 2 joints allow flexion, extension and some rotation with partly flexed knee - joint capsule is thin and it is absent anteriorly - has 12 associated bursae - reinforced by tendons – semimembranosus tendon (posteriorly) - quadriceps tendon (anteriorly) -this tendon gives rise also to the medial and lateral patellar retinaculum - reinforced by ligaments – capsular ligaments (oblique popliteal, arcuate popliteal) - extracapsular ligaments (fibular and tibial collateral ligaments) - intracapsular ligaments (anterior cruciate, and posterior cruciate ) 2. Shoulder joint (glenohumeral joint)- ball and socket joint with head of the humerus in the glenoid cavity of scapula - more mobility, less stability - reinforced by – ligaments – coracohumeral ligament - 3 glenohumeral ligaments - tendons – tendon of the long head of bicep - tendons of rotator cuff muscles 3. Elbow joint – radius and ulna articulate with humerus

- hinge joint – uniaxial, - flexion and extension movement only - reinforced by ligaments – anular ligament - 2 capsular ligaments –ulnar collateral lig radial collateral lig 4. Hip joints – or coxal joint - ball and socket joint - head of femur articulate with acetabulum - all type of movement but range of motion is limited by deep socket - strongest joint (one of the strongest structure of the body ) - acetabular labrum - has ligament from the fossa of acetabulum to the fovea capitis of the head of the femur (ligamentum teres) - reinforcing ligaments – iliofemoral - pubofemoral - ischifemoral - ligamentum teres 5. Temporomandibular joint (TMJ) – mandibular condyle articulates with the mandibular fossa of the temporal bone - most easily dislocated joint of the body - 2 types of joints: hinge –depression and elevation of mandible planar – side to side movement of mandible as in grinding of teeth Common conditions- Sprain / Strain Cartilage tears Dislocation / subluxation Bursitis / Tendonitis Arthritis - osteoarthritis - rheumatoid arthritis - gouty arthritis Lyme disease -...