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The Skeleton and Muscles Why Do We Need A Skeleton? • It supports our body (creates room for the lungs etc.) • It allows us to move • Protects vital organs • Why is the skull so thick? • To protect the brain • Why do we need ribs? • To protect the lungs and heart The Skeleton There are about 206 bones in the average human body Babies are born with 300 bones Joints • Joints are places where two bones join • They allow movement • Cartilage and synovial fluid prevent bones wearing away Parts Of The Joint • Ligaments: Hold two bones together at a joint • Cartilage: Connective tissue that prevents two bones from wearing each other out • No cartilage or synovial fluid is a cause of arthritis • Tendons: Holds muscle to bone • http://www.kidshealth.org/misc/movie/bodybasics/bodybasics_ knee.html Types Of Joints • Ball and socket e.g. hip and shoulder • Allow lots of movement • http://www.bbc.co.uk/science/humanbody/body/factfiles/joints/ball_and_socket_joint.shtml Types Of Joints • Hinge e.g. knee, elbow etc. • Allow forward and backward movement, but no sideways movement • http://www.bbc.co.uk/science/humanbody/body/factfiles/joints/hinge_joint.shtml Types Of Joints • Saddle e.g. fingers • Allow us to grasp things http://www.bbc.co.uk/science/humanbody/body/factfiles/joints/saddle_joint.shtml Types Of Joints • Fixed Joints e.g. the bone in the skull • These joints do not move http://www.bbc.co.uk/science/humanbody/body/factfiles/skull/frontal_in_skull.shtml Types Of Joints • Slightly moveable joints e.g. the vertebrae • Allow limited movement http://www.bbc.co.uk/science/humanbody/body/factf iles/spine/lumbar_vertebrae.shtml Movement • Bones cannot move on their own • They are pulled by muscles Muscles • Muscles cannot push, they can only pull when they contract • How do we push doors closed? • Muscles work in antagonistic pairs, the bicep pulls the forearm up to the upper arm, the triceps straightens the arms. We use the triceps to close a door Antagonistic Pairs The bicep flexes the arms The triceps extend the arm Muscles In The Body There are about 650 muscles in the human body Types Of Muscle • There are three types: 1. Cardiac muscle: beats on it’s own, never rests 2. Involuntary muscle: this muscle works without us thinking about it e.g. breathing, peristalsis, pupil dilation 3. Voluntary muscle: we have to think about moving these muscles e.g. skeletal muscles