The zang organs have a Chinese prefix because a direct translation from the Chinese might be misleading. The Chinese xin has functions rather different from the concept of the heart in Western medicine, so if we call the heart 'xin-heart', or the liver 'gan-liver', we are able to understand that we are referring to the organ of the heart or the liver, but it is really rather different from our concept of those organs.

The zang organs are of paramount importance in the body. They co-ordinate with the fu organs and connect with the five tissues (channels, jin¹ muscles, skin-hair, bones), and the nine openings (eyes, nose, ears, mouth, tongue, anus and external genitalia), to form the system of the Five Zang. The pericardium is not considered to be an important zang organ.

The Functions of the Zang Organs
The xin-heart
The xin-heart dominates the circulation of blood. When it functions properly the tissues and organs are well perfused and nourished, but when it malfunctions there is precordial pain, cyanosis and ischaemia. This disease is due to 'stagnation of the blood of xin-heart'.

The xin-heart 'keeps' the mind. Normally there is a clear mind, normal mentality, normal sleep and a good memory. When this fails there is coma, insomnia or somnolence, amnesia and mental derangement, because the xin-heart is failing to 'keep' the mind.

The xin-heart takes the tongue as its orifice and opens through it. Normally the tongue is reddish, moist, and moves freely. When the tongue has ulcers, is swollen or becomes purplish-red, there is 'upward blazing of the fire in xin-heart'. When the tongue is rigid and curled up (this may be accompanied by mental symptoms) 'phlegm and heat are covering the orifice of the xin-heart'.

The gan-liver
The gan-liver is the main yang organ of the body.

The gan-liver stores blood. Normally there is sufficient blood supply to all tissues. When this fails there is ischaemia, dizziness, malaise, abnormal menstruation and hemorrhage.

The gan-liver takes charge of freeing. Freeing really means the free flow of blood and qi through the body, especially digestion and the discharge of bile. When this is impaired there is irritability, mental depression, anorexia, abdominal distension and jaundice.

The gan-liver controls the jin which governs the muscle tone. When this function is disturbed there is muscle spasm, twitching, opisthotonos and convulsions. This is due to an 'insufficiency of yin and blood of the gan-liver, resulting in the malnutrition of the jin'.

The gan-liver takes the eye as its orifice and opens through it. Usually there is normal vision and normal eye movement. When this function is disturbed there is poor vision, night blindness, nystagmus and abnormal eye movements. This is due to an 'insufficiency of yin and blood in the gan-liver causing malnutrition of the eyes and stirring of the inner wind of the gan-liver.'

The pi-spleen
The pi-spleen governs the transportation and transformation of food, i.e. digestion. When digestion is abnormal there is anorexia, distension of the abdomen, diarrhea, emaciation, lassitude and oedema. This is due to 'a deficiency of the qi of pi-spleen'.

The pi-spleen commands the blood. Normally the blood circulates within the blood vessels but when this function fails there is extravasation of blood, chronic recurrent hemorrhage and bruising.