According to ancient Chinese thought, qi was the fundamental substance constituting the universe, and all phenomena were produced by the changes and movement of qi. This viewpoint greatly influenced the theory of traditional Chinese medicine. Generally speaking, the word "qi" in traditional Chinese medicine denotes both the essential substances of the human body
which maintain its vital activities, and the functional activities of the zang-fu organs and tissues.
Essential substances are the foundation of functional activities. In this sense, qi is too rarefied to be seen and its existence is manifested in the functions of the zang-fu organs. All vital activities of the human body are explained by changes and movement of qi.
Classification and production of Qi
Certain qualitative terms differentiate qi in the human body according to its source, function and distribution. These terms are: yuanqi (primary qi), zongqi (pectoral qi), yingqi (nutrient qi) and weiqi (defensive qi). In terms of their source they may be further classified into congenital qi and acquired qi. Yuanqi, which is derived from congenital essence and
inherited from the parents, is referred to as congenital qi. After birth, zongqi, yingqi and weiqi are all derived from food essence, and are therefore known as acquired qi.
Congenital qi and acquired qi are dependent on each other for their production and nourishment. Yuanqi stimulates and promotes the functional activities of the zang-fu organs and the associated tissues of the body, which in turn produce acquired qi. Thus yuanqi is the material foundation for the production of acquired qi. On the other hand, acquired qi continuously nourishes and supplements congenital qi. The relationship is such that congenital qi promotes acquired qi, which in turn nourishes congenital qi.
Qi may also describe the functional activities of the zang-fu organs and meridians. It is then referred to, for example, as qi of the heart, liver, lung, spleen, stomach, kidney and meridians.
Yuanqi (primary qi)
Derived from congenital essence, yuanqi needs to be supplemented and nourished by the qi obtained after birth from food essence. Yuanqi takes root in the kidney and spreads to the entire body via the sanjiao. It stimulates and promotes the functional activities of the zang-fu organs and the associated tissues. The more abundant yuanqi is, the more vigorously the zang-fu organs and the associated tissues will function. The human body will then be healthy
and rarely suffer from disease. On the other hand, congenital insufficiency of yuanqi, or deficiency due to a prolonged illness, may lead to various pathological changes.
Zongqi (pectoral qi)
Zongqi is formed by the combination of qingqi (clean qi) which is inhaled by the lung, and the qi of food essence which is produced by the spleen and stomach. Zongqi is stored in the chest. Its main functions are:
- To promote the lung's function of controlling respiration. The strength
or weakness of speech and respiration are related to the quality of zongqi.
- To promote the heart's function of dominating the blood and blood
vessels. The circulation of qi and blood, coldness and warmth, and the
motor ability of the four limbs and trunk are all associated with zongqi.
Yingqi (nutrient qi)
Derived from the qi of food essence produced by the spleen and stomach, yingqi circulates in the vessels. Its primary function is both to produce blood and to circulate with it, providing further nourishment. As yingqi and blood are so closely related, "ying blood" is the term commonly used to refer to their joint functions.
Weiqi (defensive qi)
Weiqi is also derived from the qi of food essence, but unlike yingqi it circulates outside the vessels. It functions to protect the muscular surface, defend the body against exogenous pathogenic factors, control the opening and closing of the pores, moisten the skin and hair, readjust body temperature, and warm up the zang-fu organs. Defending the body against exogenous pathogenic factors is its principal function, hence the name weiqi.
As mentioned above, the zang-fu and meridians possess their own qi. Originating from yuanqi, zongqi, yingqi and weiqi, the qi of the meridians (which circulates throughout the meridian system) is a combination of the qi of food essence, qingqi inhaled by the lung, and essential qi stored in the kidney. The qi of the meridians, therefore, is referred to as zhengqi
or zhenqi (vital qi) flowing in the meridians.
According to twenty-seventh chapter of Plain Questions, "Zhengqi (vital qi) means the qi of the meridians." As the basis of the functions of the meridians, the qi of the meridians greatly influences the functions of the qi, blood and zang-fu organs of the entire body.
Functions of qi
Qi acts extensively in the human body by permeating all parts. There is no place that does not have qi nor to which qi does not penetrate. If the movement of qi ceases, the vital activities of the human body will also cease. Abundant qi is the basis of good health and weakness of qi may lead to disease. Hence the statement from the Eighth Problem of Classic on Medical Problems, "Qi is the root of the human body; the stem and leaves would dry up without a root." Qi, distributed to various parts of the body, characteristically functions in the following different ways:
- Promoting function
The growth and development of the human body, the physiological activities of the zang-fu organs and meridians, the circulation of blood and distribution of body fluid, are all dependent on the promoting and stimulating effect of qi. Deficiency of qi impairs this promoting function, and thus produces pathological changes such as retarded growth and development, hypofunction of the zang-fu organs and meridians, impaired blood circulation, dysfunction
in transforming and distributing body fluid, and production of phlegm dampness in the interior.
- Warming function
The normal temperature of the body is maintained and readjusted by qi. According to the Twenty-second Problem of Classic on Medical Problems, "Qi dominates warming." The forty-seventh chapter of Miraculous Pivot says: "Weiqi warms up the muscles ..." Insufficiency of yang qi may impair its warming effect, giving rise to aversion to cold,
and cold sensations of the four limbs.
- Defensive function
Qi defends the body surface against exogenous pathogenic factors. The seventy-second chapter of Plain Questions therefore states: "The existence of the antipathogenic qi in the interior prevents the pathogenic factor from invading." Qi also combats pathogenic factors once disease occurs, and brings about recovery by eliminating the invading pathogenic factors.
- Checking function
Qi checks, controls and regulates certain bodily substances and metabolic products. For instance, qi controls blood by keeping it circulating in the vessels, and checks sweating, urination and seminal emission. If this checking function of qi is impaired, spontaneous sweating, incontinence of urine, premature ejaculation and spermatorrhoea may occur.
- Qihua (activities of qi)
Qihua has two meanings. Firstly it refers to the process of mutual transformation
among essence, qi, body fluid and blood, According to the fifth chapter of Plain Questions, "Essence is transformed into qi." In his annotation of the same chapter, Wang Bing, a physician in the Tang Dynasty says: "The activities of qi produce essence; a harmonious
supply of food essence enables the body to grow." These statements explain the mutual transformation of essence and qi.
Secondly, qihua implies certain functional activities of the zang-fu organs. According to the eighth chapter of Plain Questions, "The bladder stores body fluid, which is then excreted by the activities of qi." The activities of qi here refer to the function of the bladder
in discharging urine.
- Nourishing function
This refers to yingqi the nutrient substance formed from food. Yingqi,
which circulates in the blood vessels, is a part of blood and provides nourishment
to the whole body.
Although these six functions of qi are different, they co-operate with
and supplement each other.
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