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Chapter 9 Joints 1 Joints (articulations or arthrosis) hold bones together but permit movement Point of contact between two bones between cartilage and bone between teeth and bones Arthrology study of joints Kinesiology study of motion 2 Structural classification is based on the presence or absence of a synovial (joint) cavity and type of connecting tissue. Structurally, joints are classified as fibrous, cartilaginous, or synovial. Functional classification based upon movement: immovable synarthrosis slightly movable amphiarthrosis freely movable diarthrosis 3 Lack a synovial cavity Bones held closely together by fibrous connective tissue Little or no movement (synarthroses or amphiarthroses) Three structural types sutures syndesmoses gomphoses 4 Thin layer of dense fibrous connective tissue unites bones of the skull Immovable (synarthrosis) If fuse completely in adults is synostosis 5 Fibrous joint bones united by ligament Slightly movable (amphiarthrosis) Anterior tibiofibular joint and Interosseous membrane 6 Ligament holds cone-shaped peg in bony socket Immovable (amphiarthrosis) Teeth in alveolar processes 7 Lacks a synovial cavity Allows little or no movement Bones tightly connected by fibrocartilage or hyaline cartilage Two types synchondroses symphyses 8 Connecting material is hyaline cartilage Immovable (synarthrosis) Epiphyseal plate 9 Fibrocartilage is connecting material Slightly movable (amphiarthroses) Intervertebral discs and pubic symphysis 10 11 The articular capsule surrounds a diarthrosis, encloses the synovial cavity, and unites the articulating bones. The articular capsule is composed of two layers - the outer fibrous capsule (which may contain ligaments) and the inner synovial membrane (which secretes a lubricating and joint-nourishing synovial fluid). The flexibility of the fibrous capsule permits considerable movement at a joint, whereas its great tensile strength helps prevent bones from dislocating. Other capsule features include ligaments and articular fat pads. 12 Synovial cavity separates articulating bones Freely moveable (diarthroses) Articular cartilage Articular capsule reduces friction absorbs shock surrounds joint thickenings in fibrous capsule called ligaments Synovial membrane inner lining of capsule 13 Synovial Membrane secretes synovial fluid containing slippery hyaluronic acid brings nutrients to articular cartilage Accessory ligaments extracapsular ligaments outside joint capsule intracapsular ligaments within capsule Articular discs or menisci attached around edges to capsule allow two bones of different shapes to fit tightly increase stability of knee - torn cartilage Bursae saclike structures between structures skin/bone or tendon/bone or ligament/bone 14 Nerves to joints are branches of nerves to nearby muscles Joint capsule and ligaments contain pain fibers and sensory receptors Blood supply to the structures of a joint are branches from nearby structures supply nutrients to all joint tissues except the articular cartilage which is supplied from the synovial fluid 15 Bursae fluid-filled saclike extensions of the joint capsule reduce friction between moving structures skin rubs over bone tendon rubs over bone Tendon sheaths tubelike bursae that wrap around tendons at wrist and ankle where many tendons come together in a confined space Bursitis chronic inflammation of a bursa 16 17 Bone surfaces are flat or slightly curved Side to side movement only nonaxial Rotation prevented by ligaments Examples intercarpal or intertarsal joints sternoclavicular joint vertebrocostal joints 18 Convex surface of one bones fits into concave surface of another bone Uniaxial like a door hinge Examples Knee, elbow, ankle, interphalangeal joints Movements produced flexion = decreasing the joint angle extension = increasing the angle hyperextension = opening the joint beyond the anatomical position 19 Rounded surface of bone articulates with ring formed by another bone and ligament Monoaxial since it allows only rotation around longitudinal axis Examples Proximal radioulnar joint supination pronation Atlanto-axial joint turning head side to side “no” 20 Oval-shaped projection fits into oval (elliptical) depression Biaxial flex/extend or abduct/adduct and circumduction are possible Examples wrist and metacarpophalangeal joints for digits 2 to 5 21 One bone saddled-shaped; other bone fits as a person would sitting in that saddle Biaxial Movements are flexion-extension, abduction-adduction, and circumduction Circumduction allows tip of thumb travel in circle Opposition allows tip of thumb to touch tip of other fingers Example trapezium of carpus and metacarpal of the thumb 22 Ball fitting into a cuplike depression Multiaxial flexion/extension abduction/adduction rotation/circumduction Examples (only two) shoulder joint hip joint 23 24 Structure and shape of the articulating bone Strength and tautness of the joint ligaments Arrangement and tension of the muscles Contact of soft parts Hormones Disuse 25 Head of humerus and glenoid cavity of scapula Ball and socket Articular capsule from glenoid cavity to anatomical neck Glenoid labrum deepens socket Many nearby bursa (subacromial) Associated ligaments strengthen joint capsule Transverse humeral ligament holds biceps tendon in place All types of movement 26 Attach humerus to scapula Encircle the joint supporting the capsule Hold head of humerus in socket 27 Strength/Stability of joint-deep shoulder muscles/tendons Deep shoulder muscles: Subscapularis nearly Supraspinatus complete Infraspinatus circle Teres minor around joint Musculotendinus (rotator) cuff frequent site of injury- pitchers/ quarterbacks “tearing” supraspinatus muscle Shoulder separation- dislocation of acromioclavicular joint or displacement of humerus from glenoid cavity 28 This ball-and-socket joint is formed by the head of the femur and the acetabulum of the hipbone. This is an extremely stable joint due to the bones making up the joint and the accessory ligaments and muscles. Movements at this joint include flexion, extension, abduction, adduction, circumduction, and medial and lateral rotation of the thigh. One of strongest structures in the body 29 This is the largest and most complex joint of the body and consists of three joints within a single synovial cavity. Between femur, tibia and patella Hinge joint between tibia and femur Gliding joint between patella and femur Flexion, extension, and slight rotation of tibia on femur when knee is flexed 30 Articular capsule Patella is part of joint capsule anteriorly Rest of articular capsule is extracapsular ligaments Fibular and tibial collateral ligaments Posterior cruciate ligament Anterior cruciate ligament Lateral and medial menisci = articular discs Many bursa 31 Knee Injuries and Disorders •Knee injuries-sports •3c’s • rupture of tibial collateral ligament; •tear of anterior cruciate ligament •torn cartilage( medial meniscus) •Usually- difficult repair/recovery •Dislocated knee•displacement of tibia relative to femur •Anterior (most common)/ posterior/ medial/lateral 32 DISORDERS: HOMEOSTATIC IMBALANCES Joint Disorders Rheumatismany painful state of supporting structures of the body(bones, ligaments, joints, tendons or muscles) Arthritusrheumatism of joints Rheumatoid arthritis (RA) autoimmune disease- body attacks its own tissue Immune system attacks cartilage/joint linings Bilateral- joint on one side/opposite side Inflammation of synovial membrane untreated-membrane thickens-synovial fluid accumulates pressure- pain /tenderness Pannus- abnormal granulation-produced by membrane; erosion of articular cartilage; cartlilage destroyed; fibrous tissue joins bone ends; tissue ossifies-fusion of joint (immoveable) Treatmentnot specific- reduce pain/inflammation; preserve muscle strength/ joint function 33 DISORDERS: HOMEOSTATIC IMBALANCES Osteoarthritus ( more common than RA; less damaging) deterioration of articular cartilage; new bone formation in joint (“spurs”/bumps) decrease joint movement) Treatment-surgery-remove spurs Gouty arthritis (genetic disorder-males) Uric acid-waste product of nucleic acid metaboloism uric acid/unable to excrete; uric acid sodium urate (crystals) deposited in soft tissues/joints inflammation/swelling Treatment- diet/colchicine uric acid production Bursitis- acute chronic inflammation of a bursa housemaid’s knee/ carpet layers knee 34 DISORDERS: HOMEOSTATIC IMBALANCES Dislocation (luxation)displacement of a bone from a joint; tearing of ligaments, tendons and articular capsules Partial dislocation (subluxation)incomplete displacement of bone from a joint Sprainforced wretching/twitching of a joint with possible rupture or injury to its attachments without dislocation (luxation) possible damage-blood vessels/muscles/tendons/ligaments/or nerves Strain (less serious)overstretching of a muscle 35