As distinct from the Western medical anatomical formative definition of kidneys, the TCM concept is a functional and energetic way of describing a set of interrelated parts.
[2] The ancient book Huang Di Nei Jing Su Wen claimed that essence stored in the kidney was vital for human life, health and longevity.
Acquired jing is produced from digestion of food and water by the spleen and stomach, and respiration through the air that we breath and stored and in the kidney to be used by circulating within the body.
In the next stage physical growth finishes, and eventually declining jing leads to exhaustion of tian gui, thus extinguishing reproductive ability.
[7] kidney yang is the dynamic force necessary to start the system of balancing water metabolism, which also employs the spleen, lung, liver and san jiao.
The water gate is also responsible for regulating the opening and closing of drainage ducts, namely the bladder and anus, which rely on the activity of kidney qi.
[9] The kidney is responsible for hair luster, production of bone and brain matter, correct functioning of the ears, and regulating the opening and closing of the bladder and anus.
Mentally, its responsible for long-term memory, while emotionally it is linked to when healthy determination, or willpower (zhi) and under stress fear.