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Regular meridians and those outside the regular system constitute the Eight Extraordinary Vessels (Qi Jing Ba Mai), each with its own name. The Ren Meridian (Conception Vessel) governs the anterior aspect, while the Du Meridian (Governing Vessel) governs the posterior aspect. The Chong Meridian (Penetrating Vessel) originates at Huiyin (CV1) and travels alongside the Kidney Meridian. Yang Qiao (Yang Heel Vessel) branches from the lateral aspect of the heel and belongs to the Bladder Meridian. Yin Qiao (Yin Heel Vessel) originates at the anterior aspect and accompanies the Foot-Shaoyin Kidney Meridian. Yang Wei (Yang Linking Vessel) links all Yang meridians, and Yin Wei (Yin Linking Vessel) links all Yin meridians. The Dai Meridian (Girdle Vessel) encircles the waist like a sash; because they do not follow the standard pathways, they are called the Extraordinary Vessels.

[Note] Meridians are classified as "Extraordinary" (Qi) or "Constant" (Chang). The Twelve Regular Meridians are the Constant Meridians; the Extraordinary Vessels are not restricted by these constants, hence the name "Extraordinary." Generally, Qi and Blood in the human body normally circulate within the Twelve Regular Meridians. When the Qi and Blood in these meridians become full and overflow, they flow into other vessels and travel along separate pathways, thus named the Extraordinary Vessels. There are eight Extraordinary Vessels: Ren, Du, Chong, Dai, Yang Qiao, Yin Qiao, Yang Wei, and Yin Wei. The Ren Meridian governs the front, and the Du Meridian governs the back. The Chong Meridian is the Sea of all Meridians, and the Dai Meridian acts like a girdle on the body. Yang Qiao is a branch of the Foot-Taiyang Bladder Meridian, and Yin Qiao is a branch of the Foot-Shaoyin Kidney Meridian. Yang Wei links all Yang meridians, and Yin Wei links all Yin meridians. When Yin and Yang link each other, all meridians are regulated. Therefore, these eight vessels are like ditches set on a map to prevent flooding, avoiding the disaster of overflow. The presence of Extraordinary Vessels in the human body is analogous to this.

The *Suwen · Gukong Lun* states: The Ren Meridian originates below Zhongji (CV3). It ascends above the pubic hairline, follows the interior of the abdomen, passes through Guanyuan (CV4), reaches the throat, goes up to the chin, follows the face, and enters the eyes.
[Ren Meridian Circulation Diagram]
The *Lingshu · Wuyin Wuwei Pian* states: Both the Chong Meridian and the Ren Meridian originate in the Baozhong (Uterus/Metropolis). They ascend along the interior of the spine and serve as the Sea of the Meridians. The branches that float outwardly ascend along the abdomen, intersect at the throat, and branch off to network around the lips.

The Ren Meridian originates below Zhongji, meets the Huiyin point, ascends along the abdominal interior to Guanyuan, where it intersects with the Chong Meridian, which is the Sea of the Meridians. Its floating external branch ascends along the abdomen to the throat, branching to network the lips. After passing Chengjiang (CV26), it crosses the Foot-Yangming Stomach Meridian to reach the area between the chin and jaw, follows the face into the eye to reach Jingming (BL1), and intersects with the Du Meridian; the title "Sea of Yin Meridians" is thereby transmitted.

[Note] The Ren Meridian originates below Zhongji. Zhongji is an acupoint name, located above the pubic hairline in the lower abdomen. Below Zhongji refers to the Huiyin (CV1) acupoint below Qugu (CV2). "Ascending above the pubic hairline, following the abdominal interior to Guanyuan" means ascending internally from Huiyin to meet the Chong Meridian, as the Chong Meridian is the Sea of the Meridians. The part that floats outwardly ascends along the abdomen to the throat, branching to network the lips, ending at Chengjiang (CV26). "Ascending to the chin, following the face into the eye to Jingming" means it does not directly intersect the Du Meridian; instead, from Chengqi (ST1) of the Foot-Yangming Stomach Meridian, it ascends to the chin, follows the face, enters the inner canthus of the eye to reach Jingming (BL1) of the Foot-Taiyang Bladder Meridian, where it finally intersects with the Du Meridian, collectively known as the Sea of Yin Meridians.