The Conception Vessel, Ren Mai, is one of the eight extraordinary vessels of Chinese medicine and, with the Governing Vessel, one of the two that carry their own points. It runs up the midline of the front of the body, from the perineum to the chin, and is classed as Yin.
The sea of the yin channels
In the theory of the channels the Conception Vessel is called the sea of the yin channels, gathering and governing the yin qi of the body; the six yin principal channels are held to meet it, and it is closely tied to the reproductive and nourishing functions. With the Governing Vessel it completes the front-and-back circuit used in Daoist internal practice.
It is described here as a concept of traditional Chinese medicine, with its long documented history, rather than as a structure of Western anatomy.
In Daoist Internal Practice
With the Governing Vessel running up the spine, the Conception Vessel running down the front forms the closed loop that Daoist internal alchemy, neidan, calls the microcosmic orbit, xiao zhou tian, a meditative circuit said to carry qi from the perineum up the back to the crown and down the front to complete the cycle. Two of its points anchor the lower part of that practice, Qihai, the Sea of Qi, and Guanyuan, both over the lower abdomen at the site of the lower dantian, the alchemical furnace where jing and qi are said to be refined. Higher on the vessel, Danzhong at the sternum is one of the eight Hui, or Influential, points, specifically the meeting point for qi of the chest, and corresponds in the same scheme to the middle dantian.