Kidney - The Zang Organ

The kidney locates at either side of the lumbus. Its channel connects with the urinary bladder, with which it is externally-internally related. It opens into the ear.

1. Storing essence and dominating reproduction, growth and development. The essence in the kidney, also referred to as the yin of the kidney, consists of two parts: congenital essence inherited from the parents and acquired essence transformed from the essential substances of food. The vital essence of the kidney is an important aspect of the qi (vital functions) of the kidney, greatly influencing the function of the kidney in reproduction, growth and development. Neijing gives a precise description of the physiological function of the kidney in the process of birth, growth, full development and senility: At the age of about 14 for women and 16 for men, the qi of the kidney flourishes. Women will have the onset of menstruation, and men will have seminal emission, both signifying the power of reproduction. When women reach the age of 28 and men around 32, the qi of the kidney is at its height, the body grows and develops, reaching the prime of life. When women reach the age of 49 and men around 64, the qi of the kidney starts to decline, the body begins to wither and at the same time the function of reproduction gradually fails.
2. Producing marrow, forming up the brain, dominating the bones and manufacturing blood. The kidney stores essence which can produce marrow (including spinal cord and bone marrow). The upper part of the spinal cord connects with the brain, while the bone marrow nourishes the bones and manufactures blood. The supply to the brain, the solidity of the bones, and the adequacy of the blood are therefore all closely related to the condition of the essence of the kidney.
3. Dominating water metabolism. The part of fluid sent down by the descending function of the lung reaches the kidney. There it is divided by the yang function of the kidney into two parts: clear and turbid. The clear fluid (i.e., the part which is useful) is retained, and the turbid (i.e., the waste part) flows into the urinary bladder to form urine which is excreted.
4. Receiving qi (air). Respiration is accomplished mainly by the lung, but the kidney helps through its function of controlling reception of qi (air). The distribution of the clean qi inhaled by the lung to the whole body depends not only on the descending function of the lung but also on the kidney’s function of reception and control.
5. Opening into the ear. The auditory function is dependent upon the nourishment from the qi of the kidney. Deafness in aged people is mainly due to deficiency of the qi of the kidney.