Small Intestine receives food and fluids from the Stomach, after the Stomach has "rotted and ripened" and after the Spleen has extracted the food essences. It communicates with the Bladder, which excretes the impure fluids, and with the Large Intestine, which excretes the impure solid waste.
It further transforms the digestate by separating the "pure" part of the food and fluids from the "impure". The pure part goes to the Spleen to form part of the essences of food and fluids, which the Spleen then transports all over the body. The impure or "dirty" part of the food is passed to the Large Intestine for excretion as stool.
The impure part of the fluids are passed to the Bladder for excretion as urine. (Small Intestine has close functional relationship with Bladder and influences urination). If Small Intestine function impaired, there may be excessive urination (Deficient Yang) or scanty urination (Heat).
in pathology: Heart Fire can be transmitted to Small Intestine, which then transmits it to the Bladder. Symptoms include thirst, bitter taste in the mouth, canker sores and burning urine or hematuria.