In Traditional Chinese Medicine, Yin Heel Vessel is one of the Eight Extra Meridians. Heel vessels appear in pairs and consist of yin heel and yang heel vessel, both of which originate from below the ankle and run separately along the right and left sides of body.
Yin heel vessel is called Yin Qiao in Chinese. Qiao in Chinese means "agile and nimble movement";. Yin heel vessel has the function of regulating the muscular movements and communicating yin-yang in the body, which makes the movements of the lower limbs more vigorous and nimble.
Since yin heel vessel and yang heel vessel meet with each other at the inner canthus, they are believed to provide the nourishment for the eyes and control the opening and closing of the eyelids.
Ancient people held that yin heel and yang heel vessel govern yin-yang of the right and left sides of the whole body respectively, that is to say, yin heel vessel controls the yin of the right and left sides of the whole body while yang heel vessel controls the yang of the right and left side of the whole body.
The coalescent points
The Course of the Vessel
It starts at the posterior of the navicular bone, ascends to the upper portion of the medial malleolus, runs straight upward along the posterior border of the medial aspect of the thigh and external genitalia, then it ascends along the chest, supraclavicular fossa, running further upward lateral to the Adam's apple in front of the Renying(ST9), along the zygoma, until it reaches the inner canthus and communicates with the yang heel vessel.
You can see the corese of Yin Heel Vessel in the picture below.