7. Kidneys dominate anterior and posterior orifices
"Anterior orifice" refers to the urethra (the tube that urine passes through from the bladder to the outside of the body) and male/female genitalia, which provide urination and reproduction functions. Although the storage and excretion of urine is related to the bladder, it is dependent on the kidney's vaporization function for the production of urine. Therefore, disorders in urination such as enuresis (involuntary leakage of urine), incontinence, frequent urination, scanty urine and inability to make urine, are the result of the kidney's inability to carry out the vaporization function properly.
"Posterior orifice" refers to the anus, which excretes stool or feces. Although stool is mainly transmitted by the large intestine to the anus for excretion, the spleen plays an important part in digestion and stool production through its transformation and transportation functions. These functions need the support of the kidney to perform normally. Kidney yang provides a warm force while kidney yin provides nourishment for the spleen. In this way, the kidneys indirectly affect stool excretion. When a kidney yang deficiency is present, the spleen loses warmth and the large intestine becomes cold and under performs, leading to problems such as diarrhea. On the other hand, when kidney yin is deficient, the large intestine does not have adequate fluid for nourishment and constipation results.