 SEPUP Unit B: Activity 16

Functions Skeletal System (aka Bones) SupportMovement Protect internal organs Make blood cells Maintain body’s calcium balance

Structure of Bones Living bone cells surrounded by minerals, Hard and extremely strong Contain channels for blood vessels and nerves Spongy bone is in the center of bones. Spongy bone contains bone marrow.

Bone marrow in long bones makes blood cells Red Blood cells White blood cells Platelets

300 bones at birth Cartilage at birth forms into bone. Some bones fuse together. Adults have 206 bones. Most bones grow until age 20.

Calcium is a mineral. Makes bone hard. Needed through out the body. Bones provide calcium to the body if there is not enough in your diet. Eating dairy and calcium- rich foods is important in youth and adults to prevent osteoporosis.

 Made of muscle cells.  Contract and relax.  Contraction causes muscles to shorten.  Work in pairs.

 Hold your arm out straight.  Feel what the muscles are doing when you bend it toward your face.  Feel the biceps and the triceps muscles.

 Silvery, shiny tissue.  Attach muscle to the bone.  Tendons attach muscles to bones so that bones can move.

 Skeletal muscles.  Cardiac muscles.  Smooth muscles.

 Attach to bones for movement and to protect inner organs.  Bundles of muscle fibers are surrounded by a connective sheath.  Muscle cells are striated (striped) depending on how much actin and myosin they contain.  Movement of skeletal muscles is voluntary.

 Found only in the heart.  Can beat or pulse on their own.  When cardiac muscle cells touch each other they beat together.  Has characteristics of Smooth and Skeletal muscle. o Are involuntary (like smooth muscle). o Striated like skeletal muscle.

 Found in the walls of hollow organs like the digestive tract and walls of blood vessels.  Cells are thin and long.  They form sheets rather than bundles.  Control slow, involuntary movement.

 Contraction of the walls of the stomach and intestines.  Contraction of arteries to regulate the blood pressure and the flow of blood.

Smooth Muscle Cardiac Muscle Skeletal Muscle

 Voluntary – Actions that are under your control.  Involuntary – Actions that are not under your control.

 Skeletal muscles – walking, talking, bending.

 Smooth and Cardiac muscles – breathing, digesting, heart beating.

 Joint - Place where two bones meet.  Ligaments connect one bone to another bone.  Ligaments stabilize the joint and allow it to move.

 The skeletal/muscle system works like a lever.