joints

Joints

• Articulations

• Functions:

  • Support

  • Movement

• Fibrous joints:

  • Joined by dense connective tissue

  • Immobile

  • Ex: sutures & teeth

• Cartilaginous:

  • Joined by cartilage

    • Either hyaline or fibrocartilage

  • Slightly mobile

  • Ex: pubic symphysis, costochondral joints

• Synovial:

  • Joint cavity slightly enclosed by joint capsule

  • Articular cartilage

  • Freely mobile

  • Most joints in the body

  • General structure:

    • Joint capsule composed of fibrous layer (outer) & synovial layer (inner)

      • Synovial layer produces synovial fluid (cushions bones in joints)

    • Joint cavity is the space where synovial fluid rests

    • Ligaments strengthen joint

    • Articular cartilage provides cushioning at ends of joints

  • Joint movements:

• Range of motion:

  • The extent of degrees a joint can move

  • Determined by:

    • Structure of articular surfaces

    • Structure and tension of ligaments and joint capsules

    • Actions of muscles and tendons

• Plane joint:

  • Flat articular surfaces slide over each other

  • Multidirectional movement

  • Ex: carpals, tarsals, vertebral articular processes

• Hinge joint:

  • Convex end of bone articulates with c-shaped depression

  • Flexes & extends

  • Ex: elbow, interphalangeal joints, ankle

• Pivot joint:

  • Rounded portion of bone partially enclosed by ligament

  • Rotates

  • Ex: proximal radio-ulnar joint, atlantoaxial joint

• Ball and socket joint:

  • Rounded head of one bone fits into corresponding depression in adjacent bone

  • Multidirectional movement

  • Ex: shoulder & hip

• The shoulder:

  • Also called the glenohumeral joint

  • Found between the glenoid fossa and head of humerus (ball and socket)

  • Glenoid labrum deepens glenoid fossa

  • Loose muscular connections

    • Dislocates easily

• The elbow:

  • Among humerus, radius & ulna

  • Humeroulnar joint & humeroradial joint are hinge joints

  • Radioulnar joint is a pivot joint

• The hip:

  • Also called the coxal joint

  • Between the head of femur and acetabulum

    • Ball and socket joint

  • Acetabulur labrum deepens acetabulum

  • Ligamenetum teres carries arteries to the head of the femur

  • Tightly bound by ligaments

    • Dislocations are rare

• The knee:

  • Between femur and tibia

  • Mainly acts as hinge joint

    • Can rotate slightly when flexed

    • Can lock when fully extended

  • Supported by several ligaments

    • Medial & lateral collateral ligaments

    • Anterior & posterior cruciate ligaments

      • ACL prevents hypertension

      • PCL prevents posterior displacement of tibia

  • Menisci cushions and stabilizes

• The ankle:

  • Also called the talocrural joint

  • Among the tibia, fibula & talus

    • Talotibial and talofibular joints are hinge joints

  • Intertarsal joints are plane joints

    • Inverses & everses

  • Supported by several strong ligaments

    • More restricted motion than wrist