The Sea of Blood

Among the eight extraordinary vessels, the Penetrating Vessel, Chong Mai, holds a distinctive rank: classical sources describe it as the reservoir that the twelve regular channels draw from in times of deficiency and drain into in times of surplus, a function that earns it the title "sea of the twelve channels." Because that reservoir role centers on blood as much as on qi, it also carries the title "sea of blood," and Chinese medical gynecology has long treated it as central to the physiology of menstruation, tying disorders of menstrual timing, flow and fertility back to disturbances of this vessel specifically rather than to the regular channels alone.

Its emergence point, described in classical texts as arising from the lower abdomen alongside the Conception and Governing Vessels, associates it closely with reproductive physiology from the outset, a starting point that shapes how the vessel is used therapeutically far more than its later course, which largely tracks alongside the Kidney channel up the trunk.