Briefly, meridians and collaterals are the passages through which qi and blood circulates. In an extensive network, they cover the entire body, interior and exterior. They transport qi and blood, regulate yin and yang of the human body, and adjust physiological balance.
According to Chines medical theory, pathogenic factors come from two sources:from the human body itself, particularly emotions (such as joy, anger, melancholy, worry, grief, fear, and fright) and fron the natural world, particularly the atmospheric changes ( such as wind, cold, dryness, summer heat and humidity), together with improper diet and living habits. When a certain organ is impaired by pathogenic factors, it fails to function well. Moreover,as meridians and collaterals reach every part of the body and are connected with each other, the sick organ may send negative information to other organs through the meridians and collaterals, resulting in another sick organ. For example, cirrhosis of the liver may lead to splenomegaly, pulmonary emphysema may be complicated with pulmonary heart disease.
Along the meridians and collaterals ther are points called acupoints. They are the sites where the qi of body organs and meridians reach the body surface. Different points relate to different organs and meridians. So acupoints are the place where we can "talk" with the body and its organs.
from this review, we anc see that acupoints are the windows of the body. Futhermore, when pathological changes develop in visceral organs, there are sensations of pain, tingling, etc., at the corresponding acupoints, or round or bar-shaped acleromata, or bigger areas that are highly sensitive to pressure. This is the result of the information fo the diseased visceral organ being carried out to the body surface through the meridians. In turn, if we feed information back through the acupoints, the corresponding organ will respond. The information feedback is actually the massage, acupuncture and moxibustion applied to the acupoints. For example, patients with gastric diseases feel pain on Zusanli(ST 36) point when it is pressed .Massage on Zusanli (ST 36) will make the patient feel relieved and comfortable.