Now we know that the smallest functional unit of the skeletal muscle is our sarcomere. And the sarcomere consists of thick filaments made up of a protein known as myosin and thin filaments made up of a global protein known as actin. And this is shown in this diagram. So we have the thick filament shown in purple with the myosin heads that basically attach to our thin filament that is shown in black. Now many of these sarcomeres are connected end to end to form a very long fiber we call the myofibro. So this is our myofibril that consists of many adjacent sarcommirs that are connected end to end.