Skeleton means “dried up” in Greek--bones are actually made up of:  1/3 of water  minerals  blood and nerves You have more than 650 muscles in your body and 206 bones There are 3 types of muscles:  Skeletal (move your bones)  Cardiac (your heart)  Smooth (located in the walls of blood vessels and organs)

Outer layer is the PERIOSTEUM (peri = around) (osteo = bone) Strong layer is the COMPACT BONE (have to cut with a saw) (blood vessels and nerves run through this layer) The inner layer is the SPONGY BONE (looks like a sponge) (where bone marrow is)

LIGAMENTS- connects bone to bone TENDONS- connects muscle to bone CARTILAGE- supports bones and protects them from rubbing against each other. FIXED- don’t move HINGE- moves bones through one plane (arm, leg) BALL AND SOCKET- movement in several directions (hip and shoulder) Just a few listed here…there are many more

There are 2 types of muscles filaments: MYOSIN (thick) ACTIN (thin) When a nerve signals a skeletal muscle to contract, calcium is released inside the muscle filaments. This causes attachments to form between myosin and actin. The Sliding Filament Theory states that the actin filaments slide toward one another during contraction. The myosin filaments do not move. This shortens the muscle thus causing it to contract.

1 2 3 Attach Slide Relax

+ Muscle strength does not depend on the number of fibers in the muscles. This number is fixed before you are born. + Muscle strength depends on the thickness of fibers and how many of them contract at one time. + Thicker fibers are stronger and contribute to muscle mass. + Regular exercise stresses muscle fibers slightly, and to compensate for this added workload, the fibers increase in size.