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Definition of Joint

Definition of Joint. the point of connection between two bones or elements of a skeleton (especially if it allows motion). Structural Classification of Joints. Fibrous joints Generally immovable Cartilaginous joints Immovable or slightly moveable Synovial joints Freely moveable.

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Definition of Joint

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  1. Definition of Joint the point of connection between two bones or elements of a skeleton (especially if it allows motion)

  2. Structural Classification of Joints • Fibrous joints • Generally immovable • Cartilaginous joints • Immovable or slightly moveable • Synovial joints • Freely moveable

  3. Joints and Their Classification • Classified by freedom of movement • diarthrosis (freely movable) • amphiarthrosis (slightly movable) • synarthrosis (little or no movement) • Classified how adjacent bones are joined • fibrous, cartilaginous, bony or synovial

  4. Fibrous Joints (Synarthrosis) • Collagen fibers span the space between bones • sutures, gomphoses and syndesmoses

  5. Fibrous Joint -- Sutures • Immovable fibrous joints • bind skull bones together • Serrate - interlocking lines • coronal, sagittal and lambdoid sutures • Lap - overlapping beveled edges • temporal and parietal bones • Plane - straight, nonoverlapping edges • palatine processes of the maxillae

  6. Types of Sutures

  7. Fibrous Joint -- Gomphoses • Attachment of a tooth to its socket • Held in place by fibrous periodontal ligament • collagen fibers attach tooth to jawbone • Some movement while chewing

  8. Fibrous Joint -- Syndesmosis • Two bones bound by ligament only • interosseus membrane • Most movable of fibrous joints • Interosseus membranes unite radius to ulna and tibia to fibula

  9. Cartilaginous Joint -- Synchondrosis • Bones are joined by hyaline cartilage • rib attachment to sternum • epiphyseal plate in children binds epiphysis and diaphysis

  10. Cartilaginous Joint -- Symphysis • 2 bones joined by fibrocartilage • pubic symphysis and intervertebral discs • Only slight amount of movement is possible

  11. The Synovial Joint Figure 5.28

  12. Synovial Joint • Joint in which two bones are separated by a space called a joint cavity • Most are freely movable

  13. Features of Synovial Joints • Articular cartilage (hyaline cartilage) covers the ends of bones • Joint surfaces are enclosed by a fibrous articular capsule • Have a joint cavity filled with synovial fluid • Ligaments reinforce the joint

  14. General Anatomy • Articular capsule encloses joint cavity • continuous with periosteum • lined by synovial membrane • Synovial fluid = slippery fluid; feeds cartilages • Articular cartilage = hyaline cartilage covering the joint surfaces • Articular discs and menisci • jaw, wrist, sternoclavicular and knee joints • absorbs shock, guides bone movements and distributes forces • Tendon attaches muscle to bone • Ligament attaches bone to bone

  15. What is a Bursar? • is a small fluid-filled sac lined by synovial membrane with a inner capillary layer of slimy fluid (similar to that of an egg white). • It provides a cushion between bones and tendons and/or muscles around a joint. This helps to reduce any friction between the bones and allows free movement. • Bursae are filled with synovial fluid and are found around almost every major joint of the body; when they become inflamed, the condition is called bursitis.

  16. Knee Joint – Sagittal Section

  17. Something You Should Know About Joints…..They Act As the Fulcum Point in a Lever System.. • WHAT’S a LEVER? • And • WHY DO WE NEED THAT ANYWAY??

  18. I THOUGHT YOU WOULD NEVER ASK!!

  19. Components of a Lever • A lever is a rigid object that rotates around a fixed point called a fulcrum • Rotation occurs when effort overcomes resistance • resistance arm and effort arm are described relative to fulcrum

  20. Mechanical Advantage of a Lever • Two kinds of levers • lever that helps increase output of force • human moving a heavy object with help of crowbar • lever move object further and faster • movement of row boat with paddle • Types of levers produce either increase in speed or force

  21. Mechanical Advantage • Mechanical advantage is calculated from the length of the effort arm divided by the length of the resistance arm • Contraction of the biceps muscle causes the hand to move fast and further (MA <1.0)

  22. First-Class Lever • Has fulcrum in the middle between effort and resistance • Atlantooccipital joint lies between the muscles on the back of the neck and the weight of the face • loss of muscle tone occurs when you nod off in class

  23. Second-Class Lever • Resistance between fulcrum and effort • Resistance from the muscle tone of the temporalis muscle lies between the jaw joint and the pull of the diagastric muscle on the chin as it opens the mouth quickly

  24. Third-Class Lever • Effort between the resistance and the fulcrum • most joints of the body • The effort applied by the biceps muscle is applied to the forearm between the elbow joint and the weight of the hand and the forearm

  25. Range of Motion • Degrees through which a joint can move • Determined by • structure of the articular surfaces • strength and tautness of ligaments, tendons and capsule • stretching of ligaments increases range of motion • double-jointed people have long or slack ligaments • action of the muscles and tendons • nervous system monitors joint position and muscle tone

  26. Axes of Rotation • Shoulder joint has 3 degrees of freedom = multiaxial joint • Other joints – monoaxial or biaxial

  27. Types of Synovial Joints Based on Shape Figure 5.29a–c

  28. Types of Synovial Joints Based on Shape Figure 5.29d–f

  29. Condyloid (ellipsoid) Joints • Oval convex surface on one bone fits into a similarly shaped depression on the next • radiocarpal joint of the wrist • metacarpophalangeal joints at the bases of the fingers • Biaxial joints

  30. Gliding Joints (Also called Plane Joints) • Flat articular surfaces in which bones slide over each other • Limited monoaxial joint • Considered amphiarthroses

  31. Hinge Joints • One bone with convex surface that fits into a concave depression on other bone • ulna and humerus at elbow joint • femur and tibia at knee joint • finger and toe joints • Monoaxial joint

  32. Hinge Joint

  33. Ball-and-Socket Joints • Smooth hemispherical head fits within a cuplike depression • head of humerus into glenoid cavity of scapula • head of femur into acetabulum of hip bone • Multiaxial joint

  34. Ball in Socket Joint

  35. Pivot Joints • One bone has a projection that fits into a ringlike ligament of another • First bone rotates on its longitudinal axis relative to the other • atlantoaxial joint (dens and atlas) • proximal radioulnar joint allows the radius during pronation and supination

  36. Pivot Joint

  37. Saddle Joints • Each articular surface is shaped like a saddle, concave in one direction and convex in the other • trapeziometacarpal joint at the base of the thumb • Biaxial joint • more movable than a condyloid or hinge joint forming the primate opposable thumb

  38. Flexion, Extension and Hyperextension • Flexion decreases the angle of a joint • Extension straightens and returns to the anatomical position • Hyperextension = extension beyond 180 degrees

  39. Flexion, Extension and Hyperextension

  40. Abduction and Adduction • Abduction is movement of a part away from the midline • hyperabduction – raise arm over back or front of head • Adduction is movement towards the midline • hyperadduction – crossing fingers

  41. Elevation and Depression • Elevation is a movement that raises a bone vertically • mandibles are elevated during biting and clavicles during a shrug • Depression is lowering the mandible or the shoulders

  42. Protraction and Retraction • Protraction = movement anteriorly on horizontal plane • thrusting the jaw forward, shoulders or pelvis forward • Retraction is movement posteriorly

  43. Circumduction • Movement in which one end of an appendage remains stationary while the other end makes a circular motion • Sequence of flexion, abduction, extension and adduction movements • baseball player winding up for a pitch

  44. Rotation • Movement on longitudinal axis • rotation of trunk, thigh, head or arm • Medial rotation turns the bone inwards • Lateral rotation turns the bone outwards

  45. Supination and Pronation • In the forearm and foot • Supination • rotation of forearm so that the palm faces forward • inversion and abduction of foot (raising the medial edge of the foot) • Pronation • rotation of forearm so the palm faces to the rear • eversion and abduction of foot (raising the lateral edge of the foot)

  46. Movements of Head and Trunk • Flexion, hyperextension and lateral flexion of vertebral column

  47. Rotation of Trunk and Head • Right rotation of trunk; rotation of head

  48. Movements of Mandible • Lateral excursion = sideways movement • Medial excursion = movement back to the midline • side-to-side grinding during chewing • Protraction – retraction of mandible

  49. Movement of Hand and Digits • Radial and ulnar flexion • Abduction of fingers and thumb • Opposition is movement of the thumb to approach or touch the fingertips • Reposition is movement back to the anatomical position

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