Muscle cells, also known as myocytes, are specialized cells that make up the muscle tissue in the body. They are responsible for producing force and enabling movement. There are three main types of muscle cells: skeletal muscle cells, which are under voluntary control and help with movement; cardiac muscle cells, which make up the heart and are involuntary; and smooth muscle cells, found in organs and blood vessels, also involuntary. These cells contain proteins called actin and myosin, which interact to contract and relax, allowing muscles to function. Muscle cells can vary in size and shape depending on their type and function, but they all share the ability to generate force and respond to stimuli.