KIDNEY 7

Fluids reach the kidney after they have been absorbed by the stomach, raised upwards by the spleen, and sprinkled downwards by the lung. At this point they become differentiated into clear and turbid aspects by virtue of the transformative powers of kidney yang. The clear part of fluid essence returns to the lung, from where it moistens each one of the zang organs. From the lung, it turns into nasal discharge, or sweat, or saliva, or tears; and it differentiates into jing, blood, jin (liquids, that is the thinner fluids moistening the muscles), and ye (the denser fluids lubricating the joints and bone marrow). The turbid part feeds into the bladder, where it is being transformed into urine, and excreted.

Bone marrow is considered to be a transformation of kidney jing that has the specific task of nourishing the bones. It is differentiated into bone marrow, spinal marrow, and brain marrow. Spinal marrow feeds into the brain, where the densest concentration of "marrow" can be observed. The brain is therefore also called the sea of marrow. 

If kidney jing is plentiful, both the bone (supporting the body) and the brain (supporting the mind) will be at a level of ideal strength. On the other hand, a deficiency of kidney jing will bring about brittle bones and a listless spirit. As the Neijing puts it: "The kidney is the master of physical strength; it produces exquisite movements/actions." 

Since the teeth are considered to be the "surplus of the bones," they also rely on the nourishment of the kidney. If the jing is plentiful, the teeth are firm; if not, they come loose or fall out.

The hair's growth process is governed by the waxing and waning of kidney qi. Again the crucial Neijing quote: "At the age of seven, a female's kidney qi is in high gear, the second teeth come in and the hair grows." Ancient texts often consider the head's hair to be a direct outgrowth of the brain, which would relate it to the kidney. The growth pattern and general luster of the hair is an important indication for the condition of prenatal jing. 

Although the process of breathing is governed by the lung, the containment of incoming qi within the lower burner is governed by kidney qi. Only if kidney qi is plentiful and its grasping power sufficient can the qi passages of the lung be unobstructed and the breathing be harmonious. If the kidney is weak and the breath cannot "root" in the kidney, disease will eventually arise. Shallow breathing, particularly in patients suffering from chronic asthma, is therefore often associated with a kidney qi deficiency. In this situation, the breath gets stuck above the diaphragm and cannot descend into its rightful abode, the lower dantian. This aspect of the kidney is one reason why there is such an intent focus on abdominal breathing in Oriental cultures.

The kidney and bladder form a zang-fu pair: "The kidney is connected with the bladder," states the Neijing; "the bladder is the store house of the liquids and humors." This statement reminds us that the bladder, similar to the gallbladder and the small intestine, not only excretes unwanted waste materials, but comprises a temporary station along the body's complex highway of vital fluid transformation. Bladder function, particular its function of "opening and closing," is largely dependent on the power of kidney qi. If kidney qi is strong, normal water metabolism will take place. The storage and excretion process of water through the bladder is thus intimately related to the general functioning of the kidney. 

The ears, which faintly resemble the kidneys in shape, are thought to reflect the condition of kidney jing. Large ears and sharp hearing indicate an excellent condition of kidney jing. As people grow older, they not only become more forgetful, but their power of hearing decreases (and sometimes their ears shrivel up) as their jing depletes. As the original statement of the Neijing goes: "The kidney qi communicates with the ears; if the kidney functions properly, the ears can distinguish the five essential sounds." 

Kidney qi, due to its mother organ's close proximity to the openings in the lower burner, governs the opening and closing function of the "two private parts," including sexual functions like erection, ejaculation, and lubrication of the vaginal tract, and maintenance of fecal continence (as well as urinary continence via the control of the bladder).