It then descends to Tianzhu BL-10 in the occipital area, where the external pathway splits into two branches:
The medial branch first travels to Dazhui DU-14 below the 7th spinal process of the cervical vertebra (C7), where it meets the other Yang Primary Channels. From there, the Channel descends parallelly 1.5 cun lateral to the posterior midline.
At the level of the 2nd lumbar vertebra (L2), one sub-branch penetrates deep into the abdomen and connects to the Kidneys and the Bladder.
The main medial branch continues descending through the gluteal area and the thigh to Weizhong BL-40 on the popliteal fossa, where it rejoin the lateral branch.
The lateral branch descends to Fufen BL-41 which is 3 cun lateral to the lower border of the spinous process of the 2nd thoracic vertebra (T2). From there, it continues descending, 3 cun parallel to the posterior midline until reaching Zhibian BL-54 at the level of the fourth sacral foramen. It then runs further down to Huantiao GB-30 at the on the buttock and continues along the posterolateral aspect of the thigh to Weizhong BL-40 to meet the medial branch.
From Weizhong BL-40, the Primary Channel continues descending along the posterolateral aspect of the foreleg.
It then reaches Kunlun BL-60 at the lateral malleolus and latterly runs along the lateral border of the foot to Zhiyin BL-67 at the lateral corner of the little toenail. From there, it connects to a branch of the Kidney Primary Channel at Yongquan KID-1 and forms the Foot Yin-Yang second great circuit.
The internal pathway:
Two internal branches separates from Baihui Du-20.