Articulations or Joints

1. 8-1 Articulations or Joints Articulation or Joint Place where two bones (or bone and cartilage) come together Arthrology = study of the joints Kinesiology = study of musculoskeletal Functions of joints Give the skeleton mobility Hold the skeleton together Structure correlated with movement

2. 8-2

3. 8-3 Fibrous Joints Characteristics United by fibrous connective tissue Have no joint cavity Move little or none Types: Sutures Syndesmoses Gomphoses

4. 8-4 Fibrous Joints: Sutures Types of sutures Serrated: Opposing bones interdigitate (Sagittal suture) Lap: Overlapping beveled edges (Squamosal suture) Plane: Straight, non-overlapping edges (Intermaxillary suture) Periosteum of one bone is continuous with the periosteum of the other. In adults may ossify completely: synostosis. Fontanels: membranous areas in the suture between bones. Allow change in shape of head during birth and rapid growth of the brain after birth.

5. 8-5 Types of Sutures

6. 8-6 Fibrous Joints: Syndesmoses Two bones joined by ligament Interosseous membrane Most moveable of fibrous joints Examples: radioulnar joint and tibiofibular joints

7. 8-7 Fibrous Joints: Gomphoses Specialized joints Pegs that fit into sockets Periodontal ligaments: hold teeth in place Inflammations Gingivitis leads to… Periodontal disease

8. 8-8 Cartilaginous Joints Bones are joined by cartilage Lack a joint cavity Types Synchondroses: bound by hyaline cartilage Symphyses: bound by fibrocartilage

9. 8-9 Cartilaginous Joints: Synchondroses Joined by hyaline cartilage Little or no movement Some are temporary and are replaced by synostoses Some are permanent Some like costochondral joints develop into synovial joints Examples: Epiphyseal plates, 1st sternocostal

10. 8-10 Cartilaginous Joints: Symphyses Fibrocartilage uniting two bones Slightly movable Examples: symphysis pubis, between the manubrium and the body of the sternum, intervertebral disks.

11. 8-11 Synovial Joints Contain synovial fluid in a joint cavity called the synovial cavity Allow considerable movement (diarthroses) Most joints that unite bones of appendicular skeleton reflecting greater mobility of appendicular skeleton compared to axial

12. 8-12 Structure of Synovial Joints Articular cartilage: Hyaline cartilage that covers epiphysis Absorbs compression of joint Joint cavity (synovial cavity) Unique to synovial joints Cavity is a potential space that holds small amount of fluid Articular Capsule - a 2 layered capsule Fibrous capsule - Dense irregular c.t. Strengthens joint Synovial membrane - Loose c.t. Lines joint capsule and covers internal joint surfaces Functions to make synovial fluid Synovial fluid: Viscous fluid similar to raw egg white A filtrate of blood from capillaries in synovial membrane Contains glycoprotein molecules secre-ted by fibroblasts Nerves in capsule help brain know position of joints (proprioception)

13. 8-13 Synovial Joints with Articular Discs Some synovial joints contain an articular disc Occur in the temporomandibular joint and at the knee joint Occur in joints whose articulating bones have somewhat different shapes

14. 8-14 Bursae and Tendon Sheaths Bursae and tendon sheaths are not synovial joints Closed bags of lubricant Reduce friction between body elements Bursa – a flattened fibrous sac lined by a synovial membrane Tendon sheath – an elongated bursa that wraps around a tendon

15. 8-15 Synovial Joints: Friction-Reducing Structures

16. 8-16 Factors Influencing Joint Stabililty Articular surfaces – seldom play a major role in joint stability The elbow, the knee and the hip do provide stability Ligaments – the more ligaments in a joint, the stronger it is Muscle tone – the most important factor in joint stability Keeps tension on muscle tendons

17. 8-17 Types of Movement Gliding: in plane joints; slight movement Angular Flexion and Extension Hyperextension Plantar and Dorsiflexion Abduction and Adduction Circular Rotation Pronation and Supination Circumduction

18. 8-18 Flexion and Extension Flexion: movement of a body part anterior or posterior to the coronal plane Extension: movement of a body part posterior or anterior to the coronal plane Dorsoflexion - foot lifted toward the shin Plantar flexion - pointing toes downward Abduction: movement away from the midline Adduction: movement toward the midline

19. 8-19 Circular Movements: Rotation, Pronation and Supination Rotation: turning of a structure on its long axis Examples: rotation of the head, humerus, entire body Medial and lateral rotation; example, the rotation of the arm Pronation/Supination: refer to unique rotation of the forearm Pronation: palm faces posteriorly Supination: palm faces anteriorly Circumduction

20. 8-20 Special Movements Unique to only one or two joints Types Elevation and Depression Protraction and Retraction Opposition and Reposition Inversion and Eversion

21. 8-21 Movements at Synovial joints Monoaxial: occurring around one axis Biaxial: occurring around two axes at right angles to each other Multiaxial: occurring around several axes

22. 8-22 Types of Synovial Joints:Plane Joints Plane or gliding joints Monaxial. One flat bone surface glides or slips over another similar surface Sometimes considered an amphiarthrosis Examples: intervertebral, intercarpal, intertarsal acromioclavicular, carpometacarpal, tarsometatarsal,

23. 8-23 Hinge and Pivot Joints Hinge joints Monaxial Convex cylinder in one bone; corresponding concavity in the other Example: elbow, ankle, interphalangeal Pivot joints Monaxial. Rotation around a single axis. Cylindrical bony process rotating within a circle of bone and ligament Example: articulation between dens of axis and atlas (atlantoaxial), proximal radioulnar

24. 8-24 Saddle joints Each articular surface is shaped like a saddle; Trapeziometacarpal joint at base of the thumb

25. 8-25 Ball-and-Socket and Ellipsoid Joints Ball-and-socket Smooth heispherical head fits within a cuplike depression Multiaxial Examples: shoulder and hip joints Condyloid (ellipsoid) joint Oval convex surface on one bone fits into a similarly shaped depression on the next Atlantooccipital joint (C1-C2) Metacarpophalangeal joints

26. 8-26 The Knee Joint Most complex diarthrosis patellofemoral = gliding joint tibiofemoral = gliding with slight rotation and gliding possible in flexed position Joint capsule anteriorly consists of patella and extensions of quadriceps femoris tendon Capsule strengthened by extracapsular and intracapsular ligaments

27. 8-27 Knee, cont. Cruciate ligaments: extend between intercondylar eminence of tibia and fossa of the femur Anterior cruciate ligament (ACL). Prevents anterior displacement of tibia Posterior cruciate ligament (PCL). Prevents posterior displacement of tibia Collateral and popliteal ligaments: along with tendons of thigh muscles strengthen the joint Bursae: may result in slow accumulation of fluid in the joint (water on the knee)

28. 8-28 Knee Joint – Anterior and Posterior Views Anterior and lateral cruciate ligaments limit anterior and posterior sliding movements Medial and lateral collateral ligaments prevent rotation of extended knee

29. 8-29 Knee Joint – Superior View Medial and lateral meniscus absorb shock and shape joint

30. 8-30 Knee Injuries and Disorders Football injuries: often tear the tibial collateral ligament, the anterior cruciate ligament, and damage the medial meniscus Bursitis

31. 8-31 Inflammatory and Degenerative Conditions Arthritis – describes over 100 kinds of joint-damaging diseases Osteoarthritis – most common type – “wear and tear” arthritis Rheumatoid arthritis – a chronic inflammatory disorder Gouty arthritis (gout) – uric acid build-up causes pain in joints Lyme disease – inflammatory disease often resulting in joint pain

32. 8-32 Effects of Aging on Joints Tissue repair slows; rate of new blood vessel development decreases Articular cartilages wear down and matrix becomes more rigid Production of synovial fluid declines Ligaments and tendons become shorter and less flexible: decrease in range of motion (ROM) Muscles around joints weaken A decrease in activity causes less flexibility and decreased ROM