 Where two bones interconnect  joints  Approximately 230 movable and semi-movable joints  The structure of a joint determines the type and amount of movement that may occur  Functions  Give the skeleton mobility  Hold the skeleton together

 The three structural classifications are:  Immovable (synarthrosis)  Slightly movable (amphiarthrosis)  Freely movable (diarthrosis) or synovial joint

 The bones are close together and may interlock  Extremely strong joints  There is no joint movement Figure 8.1a Examples: 1.Suture – skull 2.Binds the teeth to bony sockets in jaw 3.Bridge between two articulating bones (first pair of ribs and the sternum)

 Permits movement  Stronger than a freely movable joint  Articulating bones are connected by cartilage or collagen fibers  Example: articulation between the two pubic bones Figure 8.2a

 Permit a wider range of motion  Typically located at the ends of long bones  Examples: upper and lower limbs

 Synovial joints all have the following:  Articular cartilage  Joint (synovial) cavity  Articular capsule  Synovial fluid  Reinforcing ligaments Figure 8.3a

 The surfaces of the articular cartilage are slick and smooth  Articular cartilages are separated by a thin film of synovial fluid  How are these two features important when it comes to movement?

 Synovial Fluid – lubrication, nutrient distribution, shock absorption  Cartilage – shock absorption, subdivide  Fat Pads – protection, packing material  Ligaments – support, strength  Tendons – limit ROM, support  Bursae – reduce friction, shock absorption

 Muscle attachment across a joint  Origin – attachment to the immovable bone  Insertion – attachment to the movable bone Nonaxial – slipping movements only Uniaxial (monaxial) – movement in one plane Biaxial – movement in two planes Multiaxial – movement in or around all three planes

 Based on the shapes of the articular surfaces  Each type of joint permits a different type and range of motion Types:  Gliding  Hinge  Pivot  Condylar  Saddle  Ball and socket

 Gliding (Plane) joints  Articular surfaces are essentially flat  Allow only slipping or gliding movements  Examples: clavicle, carpals, tarsals, sacrum-iliac Figure 8.7a

 Hinge joints  Cylindrical projections of one bone fits into a trough-shaped surface on another  Motion is along a single plane  Examples: elbow, knee, ankle, and interphalangeal joints Figure 8.7b

 Rounded end of one bone protrudes into a “sleeve,” or ring, composed of bone (and possibly ligaments) of another  Permit only rotation  Examples: joint between the axis and the dens (neck), and the proximal radioulnar joint Figure 8.7c

 Oval articular surface of one bone fits into a complementary depression in another  Biaxial joints permit movement around two axes (flexion/extension and abduction/adduction)  Examples: radiocarpal (wrist) joints, and metacarpophalangeal (knuckle) joints Figure 8.7d

 Similar to condyloid joints but with greater movement  Each articular surface has both a concave and a convex surface  Allows circumduction but prevents rotation  Example: carpometacarpal joint of the thumb Figure 8.7e

 A spherical or hemispherical head of one bone articulates with a cuplike socket of another  Multiaxial joints permit the most freely moving synovial joints  Examples: shoulder and hip joints Figure 8.7f