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Yang Wei Mai (Yang Linking Vessel) refers to the collateral branches (Sun Luo, fine collaterals) emerging from the side of Qi acupoints of the Three Yang Meridians of Hand and Foot.
Yin Wei Mai (Yin Linking Vessel) refers to the collateral branches (Sun Luo, fine collaterals) emerging from the side of Qi acupoints of the Three Yin Meridians of Hand and Foot.
Yang Qiao Mai (Yang Heel Vessel) is a branch of Zu Taiyang Bladder Meridian (Foot-Taiyang Bladder Channel), with branches connecting to Zu Shaoyin Kidney Meridian (Foot-Shaoyin Kidney Channel). In men, Yang Qiao Mai serves as the Jing (Main Meridian), and Yin Qiao Mai serves as the Luo (Collateral).
Yin Qiao Mai (Yin Heel Vessel) is a branch of Zu Shaoyin Kidney Meridian (Foot-Shaoyin Kidney Channel), with branches connecting to Zu Taiyang Bladder Meridian (Foot-Taiyang Bladder Channel). In women, Yin Qiao Mai serves as the Jing (Main Meridian), and Yang Qiao Mai serves as the Luo (Collateral).
Du Mai (Governing Vessel) is the collateral branch (Sun Luo, fine collateral) of the Du Mai running along the center of the spinal column on the back.
Ren Mai (Conception Vessel) is the collateral branch (Sun Luo, fine collateral) of the Ren Mai running along the center of the chest.
These six vessels together comprise 365 Qi acupoints. These all belong to the laterally emerging fine collaterals and do not participate in the standard degree of Ying Blood circulation.
Chong Mai (Penetrating Vessel) is known as the Sea of Blood. It descends along the right side of the abdomen and connects with the Right Kidney. Men use it to store Essence (Jing), and women use it to anchor the Bao Gong (Uterus). The Bao Gong (Uterus) is where menstruation originates, which is also referred to as Tian Gui (Heavenly Water, reproductive essence). The Nan Jing (Classic of Difficult Issues) states that the Right Kidney is the Ming Men (Gate of Life), referring to this Chong Mai running on the right side of the abdomen, opposite to the Xu Li acupoint located below the left breast. Generally, blood in the human body divides into two pathways: that which originates from below the left breast, moves with Zong Qi (Gathering Qi), and circulates within the Twelve Regular Meridians is called Ying Xue (Nutritive Blood), which nourishes the form and generates muscle tissue. That which descends from the right side of the abdomen into the Chong Mai and reaches the Right Kidney is called Tian Gui (Heavenly Water), which is responsible for reproduction and propagation. Ying Xue originates from below the left breast and circulates within the vessels; therefore, there is palpable pulsation below the left breast. Chong blood descends from the right side of the abdomen into the Right Kidney and Bao Gong (Uterus); its blood is inherently static, so there is no palpable pulsation below the right breast. This explains the difference between the left and right sides. Ying Xue nourishes the body, so it must not be injured; injury leads to death. Chong blood is for reproduction and can naturally be discharged; thus, eunuchs who have had their Chong blood damaged do not die. This is why diseases involving Ying Xue are considered particularly severe, while diseases involving Chong blood are relatively mild.
Dai Mai (Girdle Vessel) traverses horizontally through the waist, serving to connect the various meridians.
These two vessels do not participate in the standard degree of Ying Blood circulation and are similar to the fine collaterals of the regular meridians; hence, they are also classified among the Eight Extraordinary Vessels.
All these eight vessels are accumulations of blood that do not flow. The Nei Jing (Inner Canon) calls them Qi Xie Xue Luo (Abnormal Evil Blood Collaterals), while the Nan Jing calls them Qi Jing (Extraordinary Vessels). Blood circulating within the vessels is like the flow of rivers; blood overflowing into the fine collaterals is like the gathering of lakes and seas. The ancients used this principle to diagnose diseases. For instance, if blood from Yang Wei Mai overflows upwards, it results in conditions such as epistaxis (nosebleed) or gingival bleeding. If blood from Yin Wei Mai overflows downwards, it results in conditions such as hematochezia (blood in stool) or hematuria (blood in urine). If both Wei Mai suffer disease simultaneously, it results in vomiting blood or hematemesis, because their fine collaterals penetrate upwards through the Diaphragm. Diseases of Chong Mai and Dai Mai result in conditions such as metrorrhagia and leukorrhea. The Nei Jing and Nan Jing analyze these distinctions very clearly. Li Shizhen and others claimed there were separate Eight Vessels; however, this contradicts ancient classics and does not align with physiological verification. Furthermore, they falsely used this concept to support cultivation practices. Uninformed people were often deceived by this, frequently developing Lao Fei (Consumptive Disease) due to improper cultivation. I have witnessed many such cases in my life, so I elaborate on this distinction.
The above points all pertain to the actual significance of physical structure. Generally speaking, among diseases, those affecting the collaterals are the mildest, those affecting the meridians are slightly more severe, those affecting the Fu Organs are heavier still, and those affecting the Zang Organs are the most severe. This is the major method for assessing the severity of disease.
Once the actual significance of physical structure is clarified, then the Qi, Blood, Yin, and Yang attached to the physical structure can be understood. There is Zong Qi (Gathering Qi), Ying Qi (Nutritive Qi), and Wei Qi (Defensive Qi), which are detailed separately on the left.