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Chapter 8

Chapter 8. Articulations. Objectives. Contrast the major categories of joints, and explain the relationship between structures and functions for each category Describe the basic structure of a synovial joint, and describe common synovial joint accessory structures and their functions

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Chapter 8

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  1. Chapter 8 Articulations

  2. Objectives • Contrast the major categories of joints, and explain the relationship between structures and functions for each category • Describe the basic structure of a synovial joint, and describe common synovial joint accessory structures and their functions • Describe how the anatomical and functional properties of synovial joints permit dynamic movements of the skeleton • Describe the structure and function of the shoulder joint and the knee joint • Describe the effects of aging on articulations, and discuss the most common age-related clinical problems for articulations

  3. Articulations - also referred to as joints - locations of two bones interconnecting - 230 joints in the human body - determines the type and amount of movement - vary in structure and function - due to a comprise between the need for strength and mobility ex. intervertebral articulations: very strong but relatively immobile - categorized according to: - range of motion (ROM) - anatomical organization (type of tissue at joint) - more common

  4. ROM Classifications of Joints • Synarthrosis • Amphiarthrosis • Diarthrosis

  5. Anatomical Organization of Joint • Bony • Fibrous • Cartilaginous • Synovial

  6. Synarthroses - immovable joints - bones in very close contact or interlocked - extremely strong joints • four major types • Sutures • Gomphosis • Synchondrosis • Synostosis

  7. Synarthroses Cont. Sutures - edges interlocked; bound together by connective tissue ex. bones of the skull

  8. Synarthroses Cont. • Gomphosis - binds teeth to bony sockets in the maxilla and mandible - fibrous connection between a tooth and its socket is a periodontal ligament ex. between the teeth and jaws

  9. Synarthroses Cont • Synchondrosis - ridged, cartilaginous bridge between two articulating bones ex. epiphyseal cartilage 1st pair of vertebrosternal ribs and sternum

  10. Synarthroses Cont. • Synostosis - immoveable joint - created when two bones fuse and boundary disappears ex: frontal bone epiphyseal lines of mature long bones

  11. Amphiarthroses • allow more ROM than synarthroses • stronger than diarthroses • connected by collagen fibers or cartilage • two major types • Syndesmosis • Symphysis

  12. Amphiarthroses Cont. • Syndesmosis - band or ligament connect bones ex: distal tibiofibula joint

  13. Ampthiarthroses • Symphysis - wedge or pad of fibrous cartilage separates bones ex. pubic symphysis

  14. Diarthroses • allow a wide ROM • typically located at the ends of long bones • Synovial • surrounded by a fibrous articular capsule with synovial membrane ex. knee joint

  15. Components of Synovial Joints • Articular Cartilages • Synovial Fluid • Accessory Structures

  16. Components of Synovial Joints • Articular Cartilages - resemble hyaline cartilages in other areas of the body - matrix contains more water, no perichondrium (sheath - surfaces are slick and smooth (reduces friction) - do not touch, separated by a thin film of synovial fluid - if damaged matrix breaks down changing surface to rough feltwork of bristly collagen fibers • Synovial Fluid - resembles interstitial fluid, clear viscous solution - less than 3 mL even in large joints - 3 primary functions - lubrication - nutrient distribution - shock absorption

  17. Components of Synovial Joints • Accessory Structures • Cartilages and Fat Pads - meniscus: a crescent pad of fibrous cartilage situated between opposing bones within a synovial joint - subdivide a synovial cavity - channel the flow of synovial fluid - allow for variations in shape of articular surfaces - fat pads: localized masses of adipose tissue covered by a layer of synovial membrane - protect articular cartilage - act as packaging material by filling spaces as cavity changes

  18. Components of Synovial Joints Cont. • Ligaments - intrinsic: localized thickenings of the joint capsule - extrinsic: separate from joint capsule - support, strengthen, and reinforce synovial joints - can become sprained with excesses stretching; damaging collagen fibers • Tendons - not part of the articulation, pass across or around joint - may limit ROM - provide mechanical support

  19. Components of Synovial Joints Cont. • Bursae - small fluid filled pockets in connective tissue - contain synovial fluid lined with membrane - can be connected or separate from joint cavity - form where tendons/ligaments rub against tissues - reduce friction - act as shock absorbers - if develop in abnormal locations or conditions called adventitious

  20. Factors that Stabilze Synovial Joints - collagen fibers of the joint capsule and any accessory, extracapsular, or intracapsular ligament - shapes of the articulating surfaces and menisci, which may prevent movement in specific directions ex. hip joint; (head of femur projects into acetabulum) - presence of other bones, skeletal muscles, or fat pads around the joint ex. elbow - tension in tendons attached to the articulating bones

  21. Injuries to Joints • Dislocation or luxation - joint experiences extreme stress, articular surfaces ar forced out of position - can damage cartilage, tear ligaments, or distort capsule - very painful • Subluxation - partial dislocation

  22. Types of Synovial Joints • Gliding (planar) • Hinge • Pivot • Ellipsoid (condylar) • Saddle (sellaris) • Ball-and-socket

  23. Types of Synovial Joints • Ellipsoid (condylar) - oval articular surface nestles into an elliptical cavity of another bone - biaxial; along or across the length of the oval ex. radiocarpal joint, metacarpophalangeal joints 2-5, metatarsophalangeal joints • Saddle(sellaris) - each articular surface is concave along one axis and convex along the other - biaxial, permits angular motion, and circumduction - no rotation ex. 1st carpometacarpal joint (trapezium/pollex)

  24. Types of Synovial Joints • Gliding - flattened or slightly curved - flat articular surfaces glide across one another - movement is minimal ex. sacroiliac joint, intercarpal/tarsals, acromioclavicular and claviculosternal joints • Hinge - convex surface of one bone fits into the concave surface of another - permit angular motion in a single plane ex. elbow, knee, ankle, interphalangeal joints

  25. Types of Synovial Joints • Pivot - cylindrical surface of one bone rotates within a ring formed of bone and ligament - monoaxial rotation ex. atlas/axis, proximal radioulnar joint • Ball-and-socket - round head of one bone rests within a cup-shaped depression in another. - all movements allowed ex. shoulder, hip joint

  26. Describing Dynamic Motion • Linear Motion - two lines of reference - gliding forward to backward, side to side or diagonal • Angular Motion - two lines of reference - change in angle of bone - circumduction • Rotation - shaft of bone spins around its longitudinal axis

  27. Dynamic Motion Cont. • Monaxial - movement permitted along only one axis • Biaxial - movement permitted along two axis • Triaxial - movement permitted in combination of angular and rotation

  28. Types of Movement: Synovial Joints • Linear gliding - two opposing surfaces slide past one another - any direction - movement is slight, rotation is generally prevented by capsule and ligaments ex. between carpals/tarsals between the clavicle and sternum

  29. Types of Movement: Synovial Joints • Angular Motion • Flexion & Extension - flexion - movement in the anterior-posterior plane - reducing the angle between bones ex. head to chest - extension - movement in the anterior-posterior plane - increasing the angle ex. all major joints in anatomical position - past anatomical position called hyperextension

  30. Types of Movement: Synovial Joints • Abduction & Adduction - abduction: movement away from the longitudinal axis in the frontal plane ex. swinging upper limb to the side - adduction: movement towards the body ex. bringing heel of hand and finger towards body • Circumduction - moving in a circular motion ex. drawing a large circle on the chalkboard

  31. Types of Movement: Synovial Joints • Rotation - Head: - right or left • Limb • internal: anterior surface of the limb turns toward the long axis of the trunk • external: anterior surface of the limb turns away from the long axis of the trunk • pronation: turns the wrist and hand from palm facing front to palm facing back • supination: turns the wrist and hand to palm facing front (wrist in anatomical position)

  32. Special Movements • apply to specific articulations or unusual types of movement • Inversion & Eversion - inversion: twisting motion of the foot turning the sole of the foot inward - eversion: twisting motion of the foot turning the sole of the foot outward • Dorsiflexion & Plantar Flexion - dorsiflexion: flexion at the ankle joint and elevation of the sole - plantar flexion: extends at the ankle joint and elevates the heel

  33. Special Movements Cont. • Opposition - movement of thumb towards the surface of the palm or the pads of the fingers • Lateral flexion - vertebral column bends side to side • Protraction & Retraction - protraction: moving a body part anteriorly in the horizontal plane - retraction: moving a body part posteriorly in the horizontal plane

  34. Special Movements Cont. • Elevation and Depression - elevation: structure moves in a superior direction - depression: structure moves in a inferior direction

  35. Structural Components of Intervertebral Articulations • Intervertebral Discs - pad of fibrous cartilage separating vertebrae - each disc has a tough outer layer of fibrous cartilage called a anulus fibrous - attach the disc to the bodies of adjacent vertebrae - surrounds the nucleus pulposus, a soft, elastic, gelatinous core - gives disc resiliency and enables it to absorb shock - movement compresses and displaces it in the opposite direction - account for about ¼ the length of column - water content decreases with age causing injury and shortening

  36. Structural Components of Intervertebral Articulations • Intervertebral Ligaments • anterior longitudinal ligament - connects the anterior surfaces of adjacent bodies • posterior longitudinal ligament - parallels the anterior longitudinal ligament and connect the posterior surfaces of adjacent vertebral bodies • Ligamentum flavum - connects the laminae of adjacent vertebrae • Interspinous ligament - connects the spinous processes of adjacent vertebrae • Supraspinous ligament - interconnects the tips of the spinous processes from C7 to the sacrum

  37. Disc Conditions • Slipped disc - posterior longitudinal ligaments weaken (aging) - compressed nucleus pulposus may distort the anulus fibrous - forces it partially into the canal • Herniated disc - nucleus pulposus breaks through the anulus fibrous - may also protrude into canal - sensory nerves are distorted, and the protuding mass can also compress the nerves passing through the adjacent intervertebral foramen

  38. Vertebral Movements • Flexion • Extension • Lateral flexion • Rotation

  39. Shoulder Joint / Glenohumeral • ball-and-socket joint • permits the greatest ROM of any joint • dislocated frequently • diarthrosis • formed by the articulation of the head of the humerus with the glenoid cavity of the scapula • 5 ligaments • glenohumeral • coracohumeral • coracoacromial • coracoclavicular • acromioclavicular (injured during shoulder separation)

  40. Elbow Joint • hinge joint • between radius, ulna, humerus • two joints: humero-ulnar, humeroradial • extremely stable joint due to: • interlocking of bones • single thick articular capsule • strong ligaments - radial collateral ligament - annular ligament - ulnar collateral ligament

  41. Hip Joint • ball and socket joint • diarthrosis • Five ligaments - 3 broad ligaments reinforce the articular capsule - Iliofemoral - Pubofemoral - Ischiofemoral - 1 crosses the acetabular notch, filling in the gap - transverse acetabular - 1 attaches femoral head at fovea capitis to acetabulum - ligament of the femoral head or ligamentum teres

  42. Knee Joint • hinge joint • contains three separate articulations • two between the femur and tibia (condyles) • one between the patella and patellar surface of the femur • articular capsule is thin, incomplete in some areas • medial/lateral menisci between femoral and tibial surfaces • 7 major ligaments stabilizing the knee • quadriceps tendon passes over the anterior surface • patella is located in this tendon • patellar ligament continues from patella along the center of knee attaching on tibia tuberosity • patella retinaculae continue along the each side of patella attaching on tibia

  43. Knee Joint Cont. • 2 popliteal ligaments extending between femur and the heads of the tibia and fibula on posterior surface • anterior cruciate ligament connects lateral wall of the intercondylar notch to the tibial plateau between the tibial eminences • posterior cruciate ligament connects medial femoral condyle to the posterior tibia • tibial collateral ligament (MCL) reinforces medial surface, extending from the medial femoral epicondyle to the tibia • fibular collateral ligament (LCL) reinforces lateral surface, extending from the lateral fermoral epicondyle to the head of the fibula

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