Muscle cells are individual cells that comprise the muscle tissue of the body and execute muscle contraction. There are three types of muscle cells: skeletal, cardiac, and smooth. Each of these types differ in cellular structure, specific function, and location within the body. Together, the three muscle cell types play specific roles in supporting the skeletal structure and posture of the body, assisting in the flow of blood through blood vessels, aiding in digestion, and driving the heartbeat.

Skeletal muscle cells are found throughout the body, making up skeletal muscle that is anchored to the bones by ligaments. During development, skeletal muscle cells are made from precursor cells, called myoblasts, which fuse together to form long, cylindrical, mature muscle cells. Each muscle cell contains several nuclei — one from each myoblast that is used to make up the cell — and fibers that have striations where the myoblasts were fused together. Skeletal muscle cells allow for muscle contraction, and they are responsible for movement and the upright posture of the body. These cells are voluntary muscle cells, meaning they receive signals from the brain to perform contraction.

Cardiac muscle cells are found in the walls of the heart. Like skeletal muscle cells, mature cardiac muscle cells have a striated appearance, which is a result of different protein fibers within the cardiac muscle cell. Each cardiac muscle cell has a number of irregular branches, and each branch is connected to branches on neighbor cells by an adhering structure called an intercalated disc. Cardiac muscle cells are highly resistant to fatigue, and their regular contraction allows for beating of the heart, thereby pumping blood out of the heart and into the blood vessels. These cells are said to be involuntary, since they do not rely on conscious signals from the brain to contract.

Smooth muscle is structurally distinct from skeletal and cardiac muscle cells. Unlike these cell types, a smooth muscle cell does not have a striated appearance, and instead forms homogeneous bundles. Smooth muscle cells are found in a number of systems throughout the body; for example, they make up a component of veins and arteries, and surround organs in the gastrointestinal tract.

A layer of smooth muscle cells surrounds veins and arteries to provide strength and aid in movement of blood through the vessel. Smooth muscle cells also surround the esophagus, stomach, small intestines, and large intestines to aid in digestion and movement of food through the digestive system. Like cardiac muscle cells, contraction of a smooth muscle cell is involuntary and does not require conscious signals from the brain to contract and perform its functions throughout the body.