Traditional Chinese Medicine (TCM)
is one of the oldest and most mysterious form of health care, the first book on this subject is about 2500 years old, and there are indications that the Chinese were already using a crude form of TCM 4000 years ago.
Today, this medical system is widely used in China, Japan, Vietnam, Korea and all around Asia; in China alone there are 2500 hospitals specialising in TCM. This complex medical system is taught in 30 Chinese universities, to thousands of students from 120 different countries.

The origins of TCM
are found in Taoist philosophy, a system of thought attempting to describe the Universe as a closed, centred, dynamic, evolving system ruled by a set of simple natural laws that explain cyclical changes.
In the Tao, the universe is conceived as an energetic system that encompass every things and function like a living organism, as opposed to the western structuralist mechanistic concept of the world.
The concepts of totality ( TAO), Bipolarity (YIN YANG) Evolution (from the centre) Hierarchy, and Cyclical changes ( five elements ) are the foundation of Taoist thinking and permeate all component of the Chinese society to this day.
‘Tao originated from emptiness, and emptiness produced the Universe, the universe produced Qi...

Qi is the fundamental material of which the universe is constructed.

Qi,

in acupuncture and Chinese medicine is defined according to what it does and bears different names according to its function: the constitution is made of essence, Qi, mind, or ì Jing Qi Shenî also called the ìthree treasuresî.
For a healthy life, it is necessary to have Essence (Jing) a solid constitution , a good circulation of Qi, and a healthy mind (Shen).

Jing Essence
: stored in the Kidneys it circulates all over the body ;Jing controls growth, development, reproduction, sexual maturation, conception and pregnancy.
its quality and quantity determines constitutional strength. Jing is fluid like (essence) very concentrated, it is not easily replaced and it is more Yin than Qi.

Nutritive Qi
(Ying Qi) is closely related to blood, and flows into blood vessels and the 12 channels of acupuncture to nourish every parts of the body.

Defensive Qi
(Wei Qi) is the Qi which flows on the surface of the body; its main function is to protect against diseases. Compared to nutritive Qi, Wei Qi is Yang and superficial.

Main Functions of Qi:
TRANSFORMING:
(the dynamic of conception to birth to all stages of human life)
TRANSPORTING: it is the movement of Qi which is responsible for transporting blood, fluids, oxygen, nutrients in all parts of the body.
HOLDING AND RISING: it is the power of the Qi, or vitality of a person that maintain organs in their place and allow us to stand on or two feet.
PROTECTING: Wei Qi protect the body from diseases of external origins
WARMING : This is an important function of Qi, to warm the body and keep it at a constant temperature

SHEN SPIRIT
: an overall concept of vitality which includes mental stability, volition, clarity, love, compassion, and direction.

Body fluids: Jin Ye
Jin Ye includes all fluids which are not blood: tears, saliva, sweat, urine, gastric juices, synovial fluids, cerebrospinal, intracellular and extrastitial fluids.
Jin relates to clear body fluids: they circulate quickly,
Ye relates to more turbid and viscous fluids which circulates with nutritive Qi, in the interior, they move relatively slowly, their function is to moisten joints, spine, brain, bone marrow and to lubricate orifices or sense organs (eyes, mouth, ears and nose).
Jin fluids are more Yang, more exterior, Ye fluids are more Yin and interior; but Jin and Ye transform each other.
Fluids, originate in the transformation of food and Water

Qi has a dynamic role in relation to fluids: it holds fluids in place, and keeps them at constant temperature.
Fluids, to a certain extent, nourish Qi and influences its Yin/Yang balance.

Blood
is formed from the essential Qi derived from the process of digestion.
Blood without Qi is an inert substance. Blood nourishes and anchors Qi; Qi activate Blood. Both Blood and Body Fluids pertain to Yin, and weakness of Yin causes burning (drying) of Blood and Body Fluids.
Wu Tsing ‘Wu’ signifying the number Five and ‘Tsing’ meaning to do, to act, to set in motion, to move or activity, motion.The Five Phases are: Water, Fire, Wood, Metal, Earth.The connection between Yin/Yang and the Five Phases is explained by the French acupuncturist Jacques Lavier as follows:

"
Fire, connected with the summer and the south, symbolises the ‘Great Yang’ in its extreme sense while Water, connected with winter and the north symbolises the ‘Great Yin’. Wood, connected with spring and the east is the 'Diminishing Yin/Increasing Yang' or Yang growing out of Yin, Yin transforming into Yang. Metal, related to the west and the autumn, is the 'Diminishing Yang/Increasing Yin', or Yin growing out of Yang, Yang transforming into Yin".

The organs associated with Wood are the Liver and Gall Bladder. The Liver is the internal, solid, Yin organ; the Gall Bladder is the external, hollow, Yang organ.
The Fire Phase has four Meridians and three Organs associated with it; the Triple Warmer has a function but not form. The vessels form two pairs of partners:Yin: Heart and Pericardium, Yang: Small Intestine and Triple Warmer
The organs associated with Earth are the Spleen (Yin) and the Stomach (Yang). When these two are healthy and in harmony the flesh and muscle tissue is firm and has good tone.
The organs associated with Metal are the Lungs and Large Intestine, which are responsible for taking in and absorbing Pure Qi and expelling Impure Qi. The pores of the skin, which is considered to be a third lung, open and close to regulate body temperature and eliminate toxins through sweat.
The organs associated with Water are the Kidneys and Bladder. The Kidneys are the deep, Yin organ; the Bladder is the superficial, Yang organ. Weak Kidneys Qi results in the Bladder’s inability to control and hold fluids in. The Kidneys are directly related to the constitution; ageing is by definition the depletion of the power of the Kidneys. The spiritual power of Water element is will power.

The Chinese view of Physical, emotional and spiritual role of each Zang Fu implies that a dysfunction of an organ can manifest itself either physically , emotionally or spiritually.
According to TCM, excess or lack of a particular emotion affects its related organ:
these are the internal causes of disease; the seven emotions are Anger, Joy, Worry, Pensiveness, Grief, Fear, and Shock.
Anger affects the Liver: excessive anger makes the Qi rise and causes symptoms such as headache, tensions, burning eyes, etc. Repressed anger causes Qi stagnation.
Worry and pensiveness affects the Spleen, it will manifest physically as stiffness, (Spleen nourishes muscle), shallow breathing, digestive problems, stomach ulcers, diarrhoea, nausea, vomiting, gastritis, etc.
The excess of reflection/obsession would certainly interfere with the ability to absorb ideas and process them mentally.
Grief disturbs the Qi of the Lungs, and manifest itself in a variety of ‘psycho somatic’ symptoms such as breathlessness, depression, tiredness etc. If the Lungs are affected by sadness, their related Fu organ, the colon, will be affected too. Its response would be to ‘somatise’ sadness and grief in the form of irritable bowel syndrome, constipation (the inability to let go), diarrhoea (the inability to contain) ulcerative colitis etc.
Joy disturbs the Heart, The excessive Joy of the Heart is best understood as over-excitement, the continuous over stimulation of the mind caused by drugs, mental disturbances or severe and prolonged periods of stress. The Shen (mind, spirit) needs to be relaxed, peaceful; Joy makes the Qi relax and slow down. Excessive stimulation of the mind unbalances the Heart, which is Yang in nature. ìFire causes Heat to rise and disturb the mindî The Triple Heater and Pericardium are functions rather than organs they are frequently used in the treatment of mental illness.
Fear affects the Kidneys, shock scatters the Qi of both Kidneys and Heart. Fear and mental shock are said to ‘freeze’ a person; the Qi stops flowing, impairing all functions. Physically, fear generates such symptoms as palpitation, ( Heart Qi affected) urination disorders, low back pain, lack of energy; it also generates anxiety, panic attack, insomnia etc.

YIN YANG: Duality arising from the primary state has always been held as the instigator of change, change is an expression of duality, a second state of being emerging from the first. The two components of the dual power were designated as Yin and Yang.

There are four basic rules which govern the relationship between yin and yang

1) Yin and Yang Depend upon each other for Definition:
If the inside of the body is Yin and the outside is Yang they are interconnected by virtue of the fact that they are aspects of the same phenomenon.
One cannot exist without the other.

2) They Transform into Each Other:

Taking the example of Day changing into Night, Yang reaches its peak at Midday and from that moment, Yin grows out of Yang until it reaches its peak at Midnight.

3)
They Mutually Consume or Control each Other:
When one becomes dominant it has a tendency to weaken the other.
4) Yin and Yang Oppose Each Other:
like cold and hot, night and day, etc...


a) Basic Properties of Yin and Yang:
Yin
Coldness
Water
Slowness
Wetness
Substance (Solid)
Sinking
Contracting
Conserving
Interior
Darkness
Quiescence
Weakness
Inhibition

Yang
Warmth
Fire
Rapidity
Dryness
Insubstantial (Vapour)
Rising
Expanding
Transforming/Changing
Exterior
Brightness/Light
Activity
Strength
Excitement

b) Division of the Human Body according to Yin and Yang:

Yin

Internal Organs
Anterior Surface
Below the Waist
Zang Organs
Blood & Body Fluid
Ying (Nutrient) Qi
Lower Orifices

Yang

Exterior
Surfaces & Limbs (skin, flesh & muscles)
Posterior Surface
Above the Waist
Fu Organs
Qi Wei (Defensive) Qi
Upper Orifice

For more information see a brief history of Chinese medicine and Chinese principle of diet

On this link you will also find information about acupressure and moxibustion