Even though the triple warmer in TCM has its own meridian and is regarded as an organ function, it refers to the coordination of several organs and physiological functions with each other. The Upper Warmer refers to all the organs and parts from the base of the sternum upwards; the Middle Warmer includes the organs and parts in the middle region from the navel to the base of the sternum; the Lower Warmer refers to all the organs and parts from the navel downwards. Interestingly, even though the physical location of the Liver would be in the Middle Warmer, it is actually considered a Lower Warmer organ.
[San-jiao] is the "three burning cavities", and so the [Triple Burner] carries responsibilities for regulation of temperature in the body (hypothalymus) and for the coordination of the functions of the chest (for breathing), [Stomach] (for digestion) and pelvis (for excretion and reproduction); [ie] for the coordination of respiration, circulation, digestion, elimination and sexuality.
The [Small Intestine] is also an [Organ] of [Fire Yang]. The [Small Intestine] is paired with its [Yin Organ], the [Heart], and the [Triple Warmer] with the [Pericardium].