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Understanding Joints in the Human Skeleton

Learn about the structure and classifications of joints, including fibrous, cartilaginous, and synovial joints, with detailed illustrations and descriptions of different joint types and movements.

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Understanding Joints in the Human Skeleton

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  1. 9 PART 1 Joints Pages 208-222, 224-226, 228-231

  2. Joints • Rigid elements of the skeleton meet at joints or articulations • Structure of joints • Enables resistance to crushing, tearing, and other forces • Hold bones together • Allow rigid skeleton some flexibility

  3. Classifications of Joints • Joints can be classified by function or structure • Functional classification—based on amount of movement • Synarthroses—immovable; common in axial skeleton • Amphiarthroses—slightly movable; common in axial skeleton • Diarthroses—freely movable; common in appendicular skeleton/limbs (all synovial joints)

  4. Classifications of Joints • Structural classification based on • What separates the articulating bones (fibers, cartilage or joint cavity) • Structural classifications include • Fibrous • Cartilaginous • Synovial

  5. Classifications of Joints

  6. Fibrous Joints • Bones are connected by fibrous connective tissue • Do not have a joint cavity • Most are immovable or slightly movable • Types • Sutures • Syndesmoses • Gomphoses

  7. Fibrous Joints (a) Suture (b) Syndesmosis (c) Gomphosis Joint held together with very short, interconnecting fibers, and bone edges interlock. Found only in the skull. Joint held together by a ligament. Fibrous tissue can vary in length but is longer than in sutures. Peg-in-socket fibrous joint. Periodontal ligament holds tooth in socket. Socket of alveolar process Fibula Suture line Tibia Root of tooth Dense fibrous connective tissue Ligament Periodontal ligament Figure 9.1

  8. Proximal Part of the Ulna Olecranon process Radial notch of the ulna Olecranon process Head of radius Trochlear notch Head Neck of radius Neck Coronoid process Radial tuberosity Proximal radioulnar joint Interosseous membrane Interosseous membrane Ulna Ulna Radius Ulnar notch of the radius Ulnar notch of the radius Radius Head of ulna Head of ulna Styloid process of ulna Styloid process of radius Distal radioulnar joint Styloid process of ulna (a) Anterior view (b) Posterior view Styloid processof radius Figure 8.4a, b

  9. Cartilaginous Joints • Bones are united by cartilage • Lack a joint cavity • Two types • Synchondroses • Symphyses

  10. Synchondroses • Hyaline cartilage unites bones • Epiphyseal plates • Joint between first rib and manubrium (a) Synchondroses Bones united by hyaline cartilage Sternum (manubrium) Epiphyseal plate (temporary hyaline cartilage joint) Joint between first rib and sternum (immovable) Figure 9.2a

  11. Symphyses (b) Symphyses Bones united by fibrocartilage Body of vertebra Fibrocartilaginous intervertebral disc Hyaline cartilage Pubic symphysis Figure 9.2b

  12. Synovial Joints • Most movable type of joint • All are diarthroses • Each contains a fluid-filled joint cavity

  13. General Structure of Synovial Joints • Articular cartilage • Ends of opposing bones are covered with hyaline cartilage • Absorbs compression • Joint cavity (synovial cavity) • Unique to synovial joints • Cavity is a potential space that holds a small amount of synovial fluid

  14. General Structure of Synovial Joints Ligament Joint cavity (contains synovial fluid) Articular (hyaline) cartilage Fibrous capsule Articular capsule Synovial membrane Periosteum (a) A typical synovial joint Figure 9.3a

  15. General Structure of Synovial Joints • Articular capsule—joint cavity is enclosed in a two-layered capsule • Fibrous capsule—dense irregular connective tissue, which strengthens joint • Synovial membrane—loose connective tissue • Lines joint capsule and covers internal joint surfaces • Functions to make synovial fluid

  16. General Structure of Synovial Joints • Synovial fluid • A viscous fluid similar to raw egg white • A filtrate of blood • Arises from capillaries in synovial membrane • Contains glycoprotein molecules secreted by fibroblasts

  17. General Structure of Synovial Joints Ligament Joint cavity (contains synovial fluid) Articular (hyaline) cartilage Fibrous capsule Articular capsule Synovial membrane Periosteum (a) A typical synovial joint Figure 9.3a

  18. General Structure of Synovial Joints • Reinforcing ligaments • Often are thickened parts of the fibrous capsule • Richly supplied with sensory nerves

  19. General Structure of Synovial Joints Ligament Joint cavity (contains synovial fluid) Articular (hyaline) cartilage Fibrous capsule Articular capsule Synovial membrane Periosteum (a) A typical synovial joint Figure 9.3a

  20. Movements Allowed by Synovial Joints • Three basic types of movement • Gliding—one bone across the surface of another • Angular movement—movements change the angle between bones • Rotation—movement around a bone's long axis

  21. Gliding (a) Gliding movements at the wrist Gliding Joints • Flat surfaces of two bones slip across each other • Gliding occurs between • Carpals • Articular processes of vertebrae • Tarsals Figure 9.6a

  22. Angular Movements • Increase or decrease angle between bones • Movements involve • Flexion and extension • Abduction and adduction • Circumduction

  23. Angular Movements Extension Flexion (b) Angular movements: flexion and extension of the neck Figure 9.6b

  24. Angular Movements Extension Flexion (c) Angular movements: flexion and extension of the trunk Figure 9.6c

  25. Angular Movements Abduction Circumduction Adduction (e) Angular movements: abduction, adduction, and circumduction of the upper limb at the shoulder Figure 9.6e

  26. Rotation • Involves turning movement of a bone around its long axis • The only movement allowed between atlas and axis vertebrae • Occurs at the hip and shoulder joints

  27. Rotation Rotation Lateral rotation Medial rotation (f) Rotation of the head, neck, and lower limb Figure 9.6f

  28. Special Movements • Elevation—lifting a body part superiorly • Depression—moving the elevated part inferiorly Elevation of mandible Depression of mandible Elevation Lifting a body part superiorly Depression Moving a body part inferiorly Figure 9.7a

  29. Special Movements • Protraction—nonangular movement anteriorly • Retraction—nonangular movement posteriorly Protraction of mandible Retraction of mandible (b) Protraction Moving a body part in the anterior direction Retraction Moving a body part in the posterior direction Figure 9.7b

  30. Special Movements • Supination—forearm rotates laterally, palm faces anteriorly • Pronation—forearm rotates medially, palm faces posteriorly • Brings radius across the ulna

  31. Special Movements Pronation (radius rotates over ulna) Supination (radius and ulna are parallel) (c) Pronation (P) Rotating the forearm so the palm faces posteriorly Supination (S) Rotating the forearm so the palm faces anteriorly Figure 9.7c

  32. Special Movements • Opposition—thumb moves across the palm to touch the tips of other fingers Opposition (d) Opposition Moving the thumb to touch the tips of the other fingers Figure 9.7d

  33. Special Movements • Inversion and eversion • Special movements at the foot • Inversion—turns sole medially • Eversion—turns sole laterally

  34. Special Movements Inversion Eversion (e) Inversion Turning the sole of the foot medially Eversion Turning the sole of the foot laterally Figure 9.7e

  35. Special Movements • Dorsiflexion and plantarflexion • Up-and-down movements of the foot • Dorsiflexion—lifting the foot so its superior surface approaches the shin • Plantar flexion—depressing the foot, elevating the heel

  36. Special Movements Dorsiflexion Plantar flexion (f) Dorsiflexion Lifting the foot so its superior surface approaches the shin Plantar flexion Depressing the foot elevating the heel Figure 9.7f

  37. Synovial Joints Classified by Shape • Plane joint • Articular surfaces are flat planes • Short gliding movements are allowed • Intertarsal and intercarpal joints • Movements are nonaxial • Gliding does not involve rotation around any axis

  38. Plane Joint Nonaxial movement Metacarpals Carpals Gliding (a) Plane joint Figure 9.8a

  39. Synovial Joints Classified by Shape • Hinge joints • Cylindrical end of one bone fits into a trough on another bone • Angular movement is allowed in one plane • Elbow, ankle, and joints between phalanges • Movement is uniaxial—allows movement around one axis only

  40. Hinge Joint Uniaxial movement Humerus Medial/ lateral axis Ulna Flexion and extension (b) Hinge joint Figure 9.8b

  41. Synovial Joints Classified by Shape • Pivot joints • Classified as uniaxial – rotating bone only turns around its long axis • Examples • Proximal radioulnar joint • Joint between atlas and axis

  42. Pivot Joint Vertical axis Ulna Radius Rotation (c) Pivot joint Figure 9.8c

  43. Synovial Joints Classified by Shape • Condyloid joints • Allow moving bone to travel • Side to side—abduction-adduction • Back and forth—flexion-extension • Classified as biaxial—movement occurs around two axes

  44. Condyloid Joint Biaxial movement Phalanges Anterior/ posterior axis Medial/ lateral axis Metacarpals Flexion and extension Adduction and abduction (d) Condyloid joint Figure 9.8d

  45. Synovial Joints Classified by Shape • Saddle joints • Each articular surface has concave and convex surfaces • Classified as biaxial joints • 1st carpometacarpal joint is a good example • Allows opposition of the thumb

  46. Synovial Joints Classified by Shape Metacarpal 1 Medial/ lateral axis Anterior/ posterior axis Adduction and abduction Flexion and extension Trapezium (e) Saddle joint Figure 9.8e

  47. Synovial Joints Classified by Shape • Ball-and-socket joints • Spherical head of one bone fits into round socket of another • Classified as multiaxial—allow movement in all axes • Shoulder and hip joints are examples

  48. Ball-and-Socket Joint Multiaxial movement Medial/lateral axis Anterior/posterior axis Scapula Vertical axis Humerus Flexion and extension Adduction and abduction Rotation (f) Ball-and-socket joint Movement of theglenohumeral joint (a) PLAY Figure 9.8f

  49. Acromion of scapula Glenoid labrum Coracoacromial ligament Synovial cavity of the glenoid cavity containing synovial fluid Subacromial bursa Fibrous articular capsule Hyaline cartilage Tendon sheath Synovial membrane Fibrous capsule Tendon of long head of biceps brachii muscle Humerus (a) Frontal section through right shoulder joint Glenohumeral Joint- ball & socket Figure 9.11a, b

  50. Glenohumeral Joint • The rotator cuff is made up of four muscles and their associated tendons • Subscapularis • Supraspinatus • Infraspinatus • Teres minor • Rotator cuff injuries are common shoulder injuries

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