The ventricles are the two lower chambers of the heart, responsible for pumping blood out of the heart. The right ventricle sends deoxygenated blood to the lungs for oxygenation, while the left ventricle pumps oxygen-rich blood to the rest of the body. Their muscular walls are thicker than those of the atria, allowing them to generate the necessary force for blood circulation. In addition to the heart, the term ventricles also refers to fluid-filled cavities in the brain. These brain ventricles produce and circulate cerebrospinal fluid, which cushions the brain and helps maintain its chemical environment.