11.2 Muscles and Movement

The joints in our body provide mobility and hold the body together The joints in our body provide mobility and hold the body together. Most joints include the following: Bones Ligaments Muscles Tendons Nerves Interesting Note: Arthrology is the study of joints and Rheumatology is the branch of medicine devoted to joint diseases/conditions

Their Function in Movement 1. Bones – they contain several different tissues and are therefore considered organs They provide a hard framework to support the body They allow protection of vulnerable softer tissue and organs They acts as levers so movement can occur They form blood cells in their bone marrow They allow the storage of minerals (esp. Calcium and Phosphorus)

Bones involved in Movement Human adults have 206 bones

2. Muscles – for movement to occur muscles must be attached to bones and this attachment is provided by the tendons Muscles provide the force necessary for movement by shortening the length of their fibers (this is why muscles must exist as antagonistic pairs )

Ex: hamstring contracts to bend knee and quadriceps contracts to straighten knee

3. Tendons – cords of dense connective tissue

4. Ligaments – tough band-like structures that serve to strengthen the joint by connecting bone to bone; ligaments have many different types of sensory nerve endings that constantly monitor the joint to ensure no hyperextension KNEE JOINT

Human Elbow Joint Draw fully labeled joint on board

Elbow Parts and their Function Joint Part Function Cartilage Reduces friction and absorbs compression Synovial fluid Lubricates to reduce friction and provides nutrients to the cells of the cartilage Joint capsule Surrounds the joint, encloses the synovial cavity, and unites the connecting bones Tendons Attach muscle to bone Ligaments Connect bone to bone Biceps muscle Contracts to bring about flexion (bending) of arm Triceps muscle Contracts to cause extension (straightening) of arm Humerus Upper arm bone; Acts as a lever that allows anchorage of the muscles to the elbow Radius Lower, top arm bone; acts as a lever for biceps Ulna Lower, bottom arm bone; acts as a lever for triceps

Hinge Joints The elbow and the knee are both hinge joints since they permit an opening/closing type of movement Both are also one directional Both also are called synovial joints because they have a synovial cavity

Ball and Socket Joints Examples include the hip joint and shoulder joint Permits movement in several directions

Ball and Socket vs. Hinge Joints Hip Joint Knee Joint Freely movable Angular motions in many directions and rotational movements Angular motion in one direction Motions possible are flexion, extension, abduction, adduction, circumduction, and rotation Motions possible are flexion and extension Ball-like structure fits into a cup-like depression Convex surface fits into a concave surface

Definitions of Movement Flexion – decrease in angle between connecting bones Extension – increase in angle between connecting bone Abduction – movement of bone away from body midline Adduction – movement of bone toward midline Circumduction – distal or far end of a limb moves in a circle Rotation – a bone revolves around it own axis