What are meridians in Chinese medicine?

What is meridian?

Meridians are like vessels forming a network and connecting skin and muscles to internal organs such as heart, liver etc to make energy and blood flowing freely and maintain balance in the body.

How many meridians are there? There are 12 regular meridians which are the main passageways for energy and blood, six of which are foot meridians and another six are hand meridians. Foot meridians either start on the foot or end on the foot and hand meridians either start on the hand or end on the hand. These 12 meridinas connect to internal organs and are running bilaterally in the body. Apart from 12 regular meridians there are eight extra meridians which are not as regular and do not connect to internal organs directly.

Name of twelve regular meridians

Taiyin Lung Meridian of Hand or Hand's Major Yin Lung Meridian

Shaoyin Heart Meridian of Hand or Hand's Minor Yin Heart Meridian

Jueyin Pericardium Meridian of Hand or Hand's Absolute Yin Heart Protector Meridian

Shaoyang Sanjiao Meridian of Hand or Hand's Minor Yang Triple Burner Meridian

Taiyang Small Intestine Meridian of Hand or Hand's Major Yang Small Intestine Meridian

Yangming Large Intestine Meridian of Hand or Hand's Yang Supreme Large Intestine Meridian

Taiyin Spleen Meridian of Foot or Foot's Major Yin Spleen Meridian

Shaoyin Kidney Meridian of Foot or Foot's Minor Yin Kidney Meridian

Jueyin Liver Meridian of Foot or Foot's Absolute Yin Liver Meridian

Shaoyang Gallbladder Meridian of Foot or Foot's Minor Yang Gallbladder Meridian

Taiyang Bladder Meridian of Foot or Foot's Major Yang Urinary Bladder Meridian

Yangming Stomach Meridian of Foot  or Foot's Yang Supreme Stomach Meridian

 

Feature of meridians

Meridians are channel networks in human body according to Chinese medicine meridian theory. This network with many acupoints did not have anatomy basis. However modern research investigated the characteristics of meridian and acupoints and the achievement was noticeable. For example, the temperature and microcirculation perfusion at the acupoints were higher than that at nonacupoints. Some biochemical reactions were more active such as there was higher ATP, oxygen partial pressure, transcutaneous CO2 emission etc at acupoints. After acupuncture stimulation of the acupoints these parameters were changed. Also there were some researches showing that skin temperature along meridians were different from other skin area. Recently research showed that skin and deep tissue microcirculation was higher along meridians along the governor meridian which is located along the midline of the back was higher in healthy adults than non meridian part. Also blood perfusion along governor meridian was higher than that the two bilateral medial bladder meridians which located at 1.5 body inch bilateral to the midline at the back. Local blood perfusion was important for organ function. The increased microcirculation along governor meridian may represent the common features of all other 12 common meridians. Further research will provide the microcirculation information about differences between meridians and nonmeridians and its role in pathological conditions.

There are 361 acupuncture points along to these meridians. Each acupuncture point has specific effect

Acupuncture produces effect by acting through acupoints. Each acupoint has its specific effect. The mechanism of this specificity was studied. A study compared the effect of ST36, and LR3 acupoints. In this study, 26 healthy subjects were divided into three groups: ST36, LR3 and control groups. Acupuncture was received in ST36 and LR3 groups, but not control group. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiac index (CI), systemic vascular resistance index(SVRI), superior mesenteric artery blood flow volume (SMABFV), and power of each frequency domain calculated from FRV (very low frequency (VLF), low frequency (LF), high frequency (HF) and LF/HF were measured before and 30 min after stimulation. VLF: generally reflects functions such as thermoregulation and rennin-angiotensin system activity. LF generally reflects both the sympathetic and parasympathetic nervous systems. HF generally reflects the parasympathetic nervous system. LF/HL generally reflects the balance between the sympathetic and parasympathetic nervous systems. The changes in these values were found 30 min after acupuncture stimulation at ST36 and LR3 and control groups by comparing to values before the intervention. In stimulation at ST36, VLF, LF, HF and LF/HFsignificantly increased, SBP significantly decreased and SMABFV significantly increased compared with that before the intervention. In LR3 stimulation, HF significantly decreased and LH/HF significantly increased and SMABFV did not change. In control group, VLF and SVRI increased and CI significantly decreased while SMABFV did not change. This study has shown the specific effect from ST36 and LR3 which has its own unique response to acupuncture stimulation. 

Biophysical properties in meridian and acupoints

Acupuncture is an important part of Chinese medicine. It is based on meridian theory. There are 14 meridians in human body. Along the meridians, there are hundreds of acupuncture points. Acupuncture at these acupuncture points was performed. Many acupuncture points on one meridian have similar function. Current research in China showed that gastric electric activity increased when acupuncture was performed at Sibai (ST2) and Dichange (ST4) which are located in the face and on the stomach meridian, but far from stomach. It also showed that there was no effect when acupuncture was performed a nonmeridian point beside ST2 and a point on small intestine meridian. There was a study that investigated acupuncture at acupuncture points on bladder meridian, non acupuncture points on bladder meridian and non acupuncture points of bladder meridian. They found that blood flow increased the most from acupuncture with acupuncture points on bladder meridian and the least from acupuncture with non acupuncture points of bladder meridian. Recently Zhang et al showed that acupuncture off acupuncture point BL57 on bladder meridian increased local blood flow.  This effect was higher than that acupuncture off acupuncture points and off bladder meridian. They suggested that keeping needling points on meridian is more important. More research suggested that the density of nerve terminals, blood vessels and mast cells at the acupuncture points is higher and the signals produced by acupuncture are stronger. Acupuncture on the meridians facilitate the signal transporting and increase blood flow.      

There was no anatomic evidence to show meridian existence. Recent research demonstrated the existence of meridian using biophysics, biochemistry and molecular biology techniques. Li J et al reviewed the biophysical studies of meridian/acupoints after obtaining the electronic database. Researchers used the resistance measurement to detect the resistance of the acupoints. They found that there was low resistance at some acupoints compared with nonacupoints at some studies. But there were many factors affecting the measurements so there was still in a debate. There were reports that the property of transmitting sound in meridians is better than that of the surrounding areas due to the enrichment of isotropic ions along meridians under the action of bioelectric field. Main and collateral channels are good medium for mechanical vibration wave and infrasonic wave. The high temperature along meridian and acupoints was reported. Also after acupuncture treatment the temperature along the meridian and acupoints was observed. Also characteristic of transmission of light is different between meridians and nonmeridians. A relatively stable circular current of electromagnetic and chemical oscillation was found along the low electric resistance pathway. Magnetic stimulation of acupoints could cause temperature variation along meridians. Migration of isotope along meridians and myoelectric activity were observed.    

Acupuncture increases blood perfusion around the acupoints.

Acupuncture is used to treat many conditions worldwide. The mechanism is based on Meridian theory in Traditional Chinese Medicine (TCM) which is not recognized by modern medicine.  Researchers are using modern techniques to study the mechanisms of acupuncture to explain the phenomenon from modern science aspect. Li XM et al studied influence of different acupuncture manipulations at Zusanli (ST36) on skin microcirculation blood perfusion in healthy subjects. They measured local blood perfusion at ST 36 acupuncture points after acupuncture stimulation at 1min, 5 min, 10, 15min, 20 min, 25 min and 30 min. They also compared blood perfusion levels of microcirculation around the acupoints among the different manipulation techniques. They found that microcirculation around the selected acupoint was significantly increased from 1-10 min following simple needle insertion, from 5 -30 min after uniform reinforcing-reducing manipulation, from 1-30 min after reinforcing manipulation, and from 1-25 min following reducing manipulation respectively. The reinforcing manipulation was superior to other techniques. From this study we can see acupuncture increases local blood perfusion in normal subjects. The reinforcing manipulation had better effect.  

References

Li XM et al Zhen Ci Yan Jiu (2013) 38:297-300

Zhang WB et al Evid Based Complement Alternat Med (2013) 2013:426052 

Li J et al Evid Based Complement Alternat Med (2012):793841