The liver controls the stomach and spleen: Liver can actually interfere with and impair the stomach and spleen functions.
The heart controls the lungs: Heart and lungs are closely related as they are both situated in upper burner. The heart governs blood and lungs govern Qi. Qi and blood mutually assist and nourish each other.
The spleen controls the kidneys: both spleen and kidneys transform body fluids. The spleen activity in transforming and transporting fluids is essential to the kidneys transformation and excretion of fluids.
The lungs control the liver: the lungs send Qi downwards, whereas the liver spreads Qi upwards. If lung Qi is weak and cannot descend, liver Qi may tend to rise too much. When a deficiency of the lung Qi leads to rising of liver yang or stagnation of liver Qi.
The kidneys control the heart: kidneys and heart actually assist and support each other proper interaction between kidneys and heart is essential for health.