'Channels and collaterals' is a translation of the Chinese to the shape and location of the term 'jingluo'. ‘Jing’ has a geographical connotation and means a channel (e.g. a water channel) or longitude. In English it is translated as ‘channels’, elsewhere as ‘meridians’. Using the image of a tree, the ‘jing’ are like the trunk and main branches of the channel network. They generally run longitudinally through the body at a relatively deep level, and connect with the internal zangfu. Specifically they comprise the twelve primary channels, the eight extraordinary vessels and the twelve divergent channels. ‘Luo’ means ‘to attach’ or ‘a net’, and refers to the finer branches of the channel network which are more superficial and interconnect the trunk and main branches (jing), the connective tissues and cutaneous regions. In Traditional Chinese Medicine (TCM) they are referred to in general as the collaterals, and more specifically as the luo-connecting channels. There are fifteen luo-connecting channels, the twelve that belong to the twelve primary channels, the luo-connecting channels of the Conception and Governing vessels, and the great luo-connecting channel of the Spleen. The general category of the collaterals also includes the myriad ‘minute’ collaterals that are distributed throughout the body. In addition to the jing and luo, there are twelve sinew channels and twelve cutaneous regions.
The study of the channels in traditional Chinese medicine can be said to be the equivalent of the study of anatomy in Western medicine. Chinese medicine paid scant attention to the physical structure of the interior of the body, and references to the shape and location of the internal zangfu in classical texts are few and very brief. Furthermore there was no study of the distribution of the nerves, or the origin and insertion of the muscles. Traditional Chinese medicine did, however, describe in minute detail the pathways of the wide variety of channels that serve to circulate the qi and blood to every part of the body. The channels penetrate the zangfu and the extraordinary fu in the deepest levels of the body and connect with the skin, muscles, flesh, tendons, and bones, the head, body and limbs, and the sense organs, linking all the tissues and structures of the body into an integrated whole.