Chapter 9 Lever Systems- Supination and Pronation (Part 3)

Long bones

act as levers to enchance the speed or power of limb movement

lever

any elongated, rigid object that rotates around a fixed point called a fulcrum

Rotation

occurs when an effort applied overcomes resistance (load) at some other point

Mechanical Advantage

the ratio of its output force to its input force

Mechanical Advantage

calculates from length of effort arm divided by length of resistance arm

first class levers

has fulcrum in middle between effort and resistance

second class levers

resistance between fulcrum and effort

third class levers

effort between the resistance and the fulcrum

range of motion

the degrees through which a joint can move

Multiaxial Joint

shoulder joint three degrees of freedom or axes of rotation

Ball-and-Socket Joints

Smooth, hemispherical head fits within a cupcake socket

Ball-and-Socket Joint

shoulder joint- head of humerus into glenoid cavity of scapula

Condylar (Ellipsoid) Joints

Oval convex surface on one bone fits into a complementary-shaped depression on the other

Saddle Joints

both bones have an articular surface that is shaped like a saddle- concave in one direction, convex in the other

Saddle Joint

Sternoclavicular Joint

Plane (gliding) joints

flat articular surfaces in which bones slide over each other with relatively limited movement

Hinge Joints

One bone with convex surface that fits into a concave depression on other bone

Pivot Joints

One bone has a projection that is held in place by a ringlike ligament

Zero Position

the position of a joint when a person is in the standard anatomical position

Flexion

movement that decreases joint angle

Extension

movement that straightens a joint and generally returns a body part to the zero positoin

Hyperextension

further extension of a joint beyond the zero position

Abduction

movement of the body part in the frontal plane

Adduction

movement in the frontal plane back towards the midline

Elevation

movement that raises a body part vertically in the frontal plane

Depression

movement that lowers a body part in the same

Protraction

the anterior movement of a body part in the transverse plane

retraction

posterior movement

circumduction

one end of an appendage remains stationary while the other end make a circular motion

roation

movement in which a bone spins on its longitudinal axis

supination

forearm movement that turns palms to face anteriorly or upward

pronation

forearm movement that turns palm to face either posteriorly or downward