Kidney Jing plays important role in physiology

Kidney Jing plays important role in physiology. It arises from both Prenatal and Postnatal Jing. It is hereditary, like Prenatal Jing and determines ones constitution. However, it is partly replenished by the Postnatal Jing. Kidney essence is stored in the Kidneys, but has fluid-like nature and circulates all over the body. Kidney Essence is said to have the following functions: 

(i) It is the basis for growth, development, sexual maturation, and reproduction. — It moves in long, slow developmental cycles (men’s Essence flows in 8-year cycles; women’s in 7-years) and presides over the major phases of development in life. Kidney Jing declines naturally, producing the signs of aging, such as: hair/teeth loss, impairment of memory, etc. 

(ii) It is the basis for Kidney Qi — Jing is fluid-like and therefore more Yin and so can be considered as an aspect of Kidney Yin. It forms the material basis for Kidney Yin to produce of Kidney Qi. Kidney Yin is warmed by Kidney Yang and the heat from the Ming Men to produce Kidney Qi.

(iii) Kidney Jing produces Marrow — Marrow produces bone marrow, the brain, and fills the spinal cord. (Marrow in Chinese medicine has no exact equivalent in Western Medicine). The Brain in TCM is called the "Sea of Marrow". Therefore if Kidney Jing is weak, the brain may be undernourished, leading to poor memory or concentration, dizziness, a feeling of emptiness in the head, etc.

(iv) It determines our Constitution — Protection from exterior pathogens depends largely on the strength the Defensive (Wei Qi), as discussed below.

(v) Jing and Qi are the material foundation for Shen (Mind) — This postulate is used in Chinese medicine because Jing, Qi and Shen represent three different states of the condensation of "Qi", from coarse, to rarified, to subtle and immaterial, respectively. If Jing and Qi are healthy and plentiful, the Mind will be happy. If both Jing and Qi are deficient, the Mind will suffer.