Breathing Basics: How Does The Diaphragm Work? As part of your Level 2 and 3 anatomy exam, you need to understand the diaphragm and how this relates to breathing. The diaphragm is a large, dome-shaped muscle located at the base of the chest cavity, separating the chest (or thoracic cavity) from the abdomen. It's one of the primary muscles involved in the breathing process. 💨 Inhalation (Breathing In): When you inhale, your diaphragm gets a signal to contract. As it contracts it moves downward,