Muscular & Skeletal Systems a.k.a. The Musculoskeletal System

The Skeletal System

Bones Provide support for the body Form the body’s shape Very lightweight, but strong enough to support body weight 206 bones in the body

Inside a Bone Compact bone – the solid, hard outside part of the bone Cancellous bone – spongy, inside the compact bone Bone marrow – inside of the bone; where most of the blood cells are made (make a connection to another system)

Between the Bones Ligaments – long, fibrous straps that connect bones to other bones Cartilage – flexible, rubbery substance; supports bones and protects them when they rub against each other

Types of Bones Short bones – chunky, wide bones; feet and wrists Long bones – a bone that is significantly longer than it is wide; arm and leg bones Flat bones – plate-like bones, have a flat shape; ribs and shoulder blades Irregular bones – have odd shapes and don’t fit into any other category, vertebrae

The Muscular System

Muscles Muscles pulls on the joints, allowing us to move Help the body perform other functions necessary for life, such as digesting food (make another connection here) More than 650 muscles – half of a person’s body weight 3 types of muscle…

Skeletal Muscle attached to bone, mostly in the legs, arms, abdomen, chest, neck, and face Striated muscles (made up of fibers that have horizontal stripes) Hold the skeleton together, give the body shape and help it with everyday movements Voluntary (you can control their movements)

Smooth Muscle Found in the stomach and small intestines; blood vessels (more connections here) Looks smooth, not striated Involuntary (you don’t control the movements, they are controlled by the nervous system automatically)

Cardiac Muscle Found in the heart walls of the heart's chambers are composed almost entirely of muscle fibers Involuntary (you don’t control the movements, they are controlled by the nervous system automatically)

Joints Allow our bodies to move in many ways Classified by their range of movement (3 types) Immovable (fibrous) joints don’t move dome of the skull Teeth in the jaw bone Partially movable (cartilaginous) joints move a little Spine (linked by cartilage)

Freely movable (synovial) joints Move in many directions Filled with synovial fluid Hinge joints move in one direction Elbow, knee Pivot joints allow a rotating or twisting motion Neck, wrist Ball-and-socket joints allow the greatest freedom of movement Hip, shoulder

Movement Tendons – connects bones to the skeletal muscles Muscle cells – only cells in the body that can shorten (contract) Flexor – muscle that causes a joint to bend when it contracts Extensor – muscle that causes a joint to straighten when it contracts

For more information check out… http://kidshealth.org/teen/y our_body/body_basics/bones _muscles_joints.html#