Transcript Chapter 3
Chapter 9 Joints 1 INTRODUCTION • Joint = point of contact – between 2 bones – between cartilage and bone – between teeth and bone • Joints hold bones together but permit movement • Arthrology = study of joints • Kinesiology = study of motion 2 I. Classification of Joints • Structural classification based on: – presence or absence of a synovial (joint) cavity – type of connective tissue – three structural classifications • fibrous – do not have synovial cavity – held together by fibrous C.T. (lots of collagen) • cartilaginous – no synovial cavity – bones held together by cartilage • synovial – bones forming joint have a synovial cavity – dense irreg. C.T. & accessory ligaments of articular capsule holds bones together 3 I. • Classification of Joints Functional classification based on degree of movement allowed by joint: 1) Synarthrosis = immovable 2) Amphiarthrosis = slightly movable 3) Diarthrosis = freely movable 4 II. A. Fibrous Joints • No synovial cavity • Articulating bones held closely together by fibrous C.T. • Allow limited movement • 3 structural types – sutures – syndesmoses – gomphoses 5 Sutures • Thin layer of dense fibrous connective tissue uniting bones of the skull • Irregular/interlocking edges give added strength & prevent fracture • Synarthrosis because immovable • Synostosis = suture that has fused completely & been replaced by bone 6 Syndesmoses • Greater distance btwn articulating bones & more fibrous C.T. than sutures • Arrangements of C.T. – bundles = ligament – sheets = inteross. memb. • Amphiarthrosis: limited movement • Examples – Anterior tibiofibular joint – Interosseous membranes in forearm and leg 7 Gomphoses • Dentoalveolar joints: cone-shaped pegs in bony socket • Synarthrosis • Only example = teeth in alveolar processes of maxillae and mandible 8 B. Cartilaginous Joints • Lack a synovial cavity • Allows limited movement • Articulating bones tightly connected by fibrocartilage or hyaline cartilage • 2 types – synchondroses – symphyses 9 Synchondrosis • Connecting material = hyaline cartilage • Synarthrosis • Examples: – epiphyseal plates – articulation of first rib w/ manubrium of sternum – become synostoses when bone replaces cartilage 10 Symphysis • Ends of articulating bones covered w/ hyaline cartilage • Thin disc of fibrocart. connects bones • All occur in midline of body • Amphiarthrosis • Examples: – intervertebral disc – pubic symphysis 11 C. Synovial Joints • Synovial cavity separates articulating bones • Freely moveable (diarthroses) • Articular cartilage covers articulating bones – reduces friction – absorbs shock • Three structural components: – Articular capsule – Synovial membrane/fluid – Accessory ligaments/discs 12 Structural Components: Articular Capsule • Surrounds joint, encloses synovial cavity, & unites articulating bones • Two layers – outer fibrous capsule • usually dense irregular C.T. • attaches periosteum of articulating bones • flexibility permits considerable movement, but tensile strength prevents dislocation • forms ligaments (dense CT) when arranged in bundles – inner synovial membrane • secretes a lubricating synovial fluid • sometimes contains articular fat pads – EX: infrapatellar fat pads 13 Structural Components, ctd • Synovial fluid – Mixture of hyaluronic acid secreted by synovial membrane & interstitial fluid – Lubricates joints & absorbs shock – Provides nutrients to/removes wastes from articular capsule – Phagocytes remove microbes – Immobility of joint increases viscosity, activity decreases viscosity 14 Structural Components, ctd • Accessory ligaments & articular discs/menisci – extracapsular ligaments lie outside joint capsule – intracapsular ligaments lie within capsule – articular discs (menisci) = pads of fibrocartilage btwn bones • attached to capsule • allow 2 bones of different shape to fit tightly • maintain stability of joint 15 Nerve and Blood Supply of Synovial Joints • Nerves to joints are branches of nerves that supply muscles that move joint • Many nerve endings distributed to articular capsule & accessory ligaments – sense pain – relay information about degree of stretch/movement • Many components are avascular but arteries can penetrate ligaments/capsule – deliver nutrients to joint – veins remove CO2 & wastes • pass from chondrocytes to synovial fluid to vein • pass directly from all other joint structure to vein 16 Bursae and Tendon Sheaths • Bursae – Fluid-filled saclike structures that alleviate friction in some joints – Resemble joint capsules • Walls consist of C.T. & synovial membrane – Fluid similar to synovial fluid – Located between: • Skin/bone • Tendon/bone or ligament/bone • Muscle/bone • Bursitis = chronic inflammation of a bursa 17 Bursae and Tendon Sheaths • Tendon sheaths = tubelike bursae that wrap around tendons that experience large amounts of friction – where tendon enters synovial cavity • Biceps brachii @ shoulder – where many tendons come together in small space • Wrist/ankle – where there is considerable movement • Fingers/toes • Bursae & tendon sheaths reinforce the articular capsule 18 Types of Movements at Synovial Joints Four main categories of joint movement (Table 9.1) 1) Gliding movements • flat bone surfaces move back and forth & side to side with respect to one another • no significant alteration of angle between bones • limited in range because of structure of capsule/ligaments • Ex: intercarpal or intertarsal joints (planar joints) 19 Types of Movements at Synovial Joints 2) Angular movements • Increase or decrease in angle btwn articulating bones • Measured with respect to anatomical position • Covered in lab • Flexion/extension, lateral extension, hyperextension • Abduction/adduction, circumduction 20 Types of Movements at Synovial Joints 4) Special movements – Occur only at certain joints – 11 different special movements • Elevation/depression: upward/downward motion • Protraction/retraction: movement in transverse plane • Inversion/eversion: movement of soles medially/laterally • Dorsiflextion/plantarflexion: bending of ankle in direction of superior/inferior surfaces • Supination/pronation: movement of prox/distal radioulnar joints which turns palms anteriorly/posteriorly • Opposition: movement of carpometacarpal joint in which thumb touches fingers of same hand 21 Types of Synovial Joints • ***These will be covered in lab, so they will be minimally discussed in lecture. However the notes may be useful to you in studying for the lab exam.*** • Varying shapes of bones/joints allow numerous movements • 6 types – Planar – Hinge – Pivot – Condyloid – Saddle – Ball & socket 22 1. Planar Joint • Articulating surfaces flat or slightly curved • Primarily allow gliding movements • Rotation prevented by ligaments • Nonaxial because motion does not occur around axis or along plane • Examples – intercarpal or intertarsal joints – sternoclavicular joint – vertebrocostal joints 23 2. Hinge Joint • Convex surface of one bone fits into concave surface of another • Monaxial: allows motion around single axis – produces angular opening & closing – flexion/extension only • Examples – Knee, elbow, interphalangeal joints 24 3. Pivot Joint • Rounded/pointed surface of bone articulates with ring formed by 2nd bone & ligament • Monaxial: rotation around own axis • Examples – Proximal radioulnar joint • supination • pronation – Atlanto-axial joint • nodding head “no” 25 4. Condyloid (Ellipsoidal) Joint • Convex oval-shaped projection articulates with oval depression • Biaxial: allows motion along two axes – flexion/extension – abduction/adduction/circumduction • Examples: wrist & metacarpophalangeal joints for digits 2 to 5 26 5. Saddle Joint • Articulating surface of one bone saddled-shaped; other bone fits into “saddle” • Modified condyloid joint • Biaxial – Circumduction allows tip of thumb travel in circle – Opposition allows tip of thumb to touch tip of other fingers • Example: carpo/metacarpal joint of wrist/thumb 27 6. Ball and Socket Joint • Ball-like head of long bone fits into a cup-like socket • Multiaxial: motion around 3 axes & all directions in between – flexion/extension – abduction/adduction – rotation • Examples: – shoulder joint: humerus in glenoid – hip joint: femur in acetabulum 28 III. CONTACT & RANGE OF MOTION AT SYNOVIAL JOINTS • • Range of motion (ROM) = range (measured in degrees of circle) thru which bones of joint can move Several factors contribute to keeping articular surfaces in contact & affect ROM: 1) 2) 3) 4) 5) 6) 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 29 IV. ETC… • Arthroscopy = examination of joint w/ pencil-sized instrument – removes torn knee cartilages & repair ligaments – requires only small incision • Arthroplasty = joint replacement – hip & knee replacements common • Dislocation of a joint = luxation – refers to displacement of a bone from a joint – torn tendons, ligaments, capsules accompany dislocation – subluxation = partial dislocation 30 ETC… • Sprain – forcible twisting of joint that stretches or tears ligaments – no dislocation of the bones – may damage nearby blood vessels, muscles or tendons or nerves – swelling & hemorrhage from damaged blood vessels – ankle & back are common sprain sites • Strain – overstretched or partially torn muscle – results from sudden, powerful contraction 31 DISORDERS: HOMEOSTATIC IMBALANCES: • Osteoarthritis – degenerative joint disease commonly known as “wearand-tear” arthritis – characterized by deterioration of articular cartilage and bone spur formation – noninflammatory – primarily affects weight-bearing joints • Gouty arthritis – sodium urate crystals deposited in soft tissues of joints causing inflammation, swelling, and pain – If not treated, bones @ affected joints eventually fuse, rendering joints immobile 32 Rheumatoid Arthritis • Autoimmune disorder: body attacks its own cartilage & joint linings • Inflammation of synovial membrane – accumulation of synovial fluid causes swelling, pain & loss of function – eventually, fibrous tissue in joints becomes ossified joint becomes immovable • Occurs bilaterally 33