The diaphragm is the primary muscle responsible for breathing in the human body. This dome-shaped muscle separates the chest cavity from the abdominal cavity and plays a crucial role in respiration. Upon inhalation, the diaphragm contracts and moves downward, creating negative pressure in the chest cavity, which allows air to be drawn into the lungs. During exhalation, the diaphragm relaxes and moves back to its original position, pushing air out of the lungs. The diaphragm works alongside intercostal muscles and other respiratory muscles to facilitate effective breathing, making it essential for maintaining proper oxygen levels in the body.