11.2 Muscles and Movement

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 JointDraw fully labeled joint on board

Elbow Parts and their FunctionJoint 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 JointsHip Joint Knee Joint

Freely movable Freely movableAngular 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