The circulatory system is affected by posture and gravity - both on the surface of the earth and during spaceflight. The circulation has also been understood to be a closed loop system since the work of William Harvey almost 400 years ago. Nonetheless, no current model of the circulation takes both of those observations fully into account. This monograph builds a new model of the systemic circulation step-by-step, applying fundamental principles of physics and hydraulics. The result is a conceptual model that is robust enough to work in any force environment - explaining both old and new observations that range from aerospace physiology to blood flow to the brain of the standing the giraffe, to everyday clinical observations at the bedside.
