经云∶膀胱者，州都之官，津液藏焉，气化则能出矣。又云∶膀胱当十九椎，居肾之
下，大肠之前。有下口，无上口。当脐上一寸水分穴处，为小肠下口，乃膀胱上际，水
液由此别回肠随气泌渗而入。其出入皆由气化，入气不化，则水归大肠，而为泄泻。出
气不化，则闭塞下窍，而为癃肿也。是经多血少气。
《难经》曰∶膀胱重九两二铢，纵广九寸，盛尿九升九合，口广二寸半。
\r足太阳膀胱腑图\p06-d43a64.bmp\r
膀胱足太阳之脉，起于目内 ，上额交颠。其支者，从颠入络脑，还出别下项，循
肩，内侠脊，抵腰中，入循膂络肾，属膀胱。其支者，从腰中下挟脊，贯臀入 中。其
支者，从 内左右，别下贯胛，挟脊，内过髀枢，循髀外从后廉下合 中，以下贯 内，
出外踝之后，循京骨到小趾外侧。
\r膀胱经循行图\p06-d43a66.bmp\r
足太阳经膀胱脉，目内 上起额尖。支者颠上至耳角，直者从颠脑后悬，络脑还出
别下项，仍循肩膊侠脊边，抵腰膂肾膀胱内，一支下与后阴连。贯臀斜入委中穴，一支膊
内左右别，贯胛侠脊过髀枢，臂内后廉 中合，下贯 内外踝后，京骨骨下趾外侧。
【注】足太阳之脉，起目内 睛明穴，从睛明循行攒竹、曲差、五处，上额交颠，入
承光穴，从承光循行通天穴。其支者，从颠至耳上角，交于足少阳之经。其直者，从通
天入络于大杼穴，从大杼循行肩 内风门穴，从风门循行肺俞穴，挟脊抵腰中厥阴俞穴，从
厥阴俞穴循行心俞、膈俞、肝俞、胆俞、脾俞、胃俞、三焦俞，入循膂络肾，从肾俞穴
循行气海俞，从腰中下挟脊大肠俞穴，从大肠俞循行关元俞、膀胱俞、中膂俞，白环俞
等穴，别行上 、次 、中 、下 等穴。其支者，又复上肩膊内，从附分穴循行贯胛魄
户穴，从魄户循行挟脊内膏肓、神堂、 、
膈关、魂门、阳纲、意舍、胃仓、肓门、志室、胞肓等穴，过髀枢秩边穴，从秩边穴循
髀外从后廉、承扶、浮 、委阳穴，下合 中委中穴，从委中循行合阳穴，从合阳下贯
内承筋穴，从承筋循行承山、飞扬、附阳等穴，从附阳穴循行出外踝之后昆仑穴，从昆
仑穴循行仆参、伸脉、金门等穴，循京骨即本经之京骨穴也。从京骨循行束骨、通谷穴，
至小趾外侧至阴穴而终，以交于足之少阴经也。
医经记载：膀胱是州都之官（指膀胱为津液汇聚之所），津液在其中贮藏，经过气化作用才能排出体外。又说：膀胱位于第十九椎处，在肾脏下方，大肠前方。它只有一个下口，没有上口。在肚脐上一寸的水分穴处，是小肠的下口，也是膀胱的上界，水液由此与回肠分离，随着气机的运行渗注进入膀胱。其进入和排出都依赖气化功能，如果入气不能气化，水液就会流入大肠，导致泄泻；如果出气不能气化，就会闭塞下窍，导致小便不通或肿胀。这条经脉多血少气。
《难经》说：膀胱重九两二铢，纵横各九寸，能盛装尿液九升九合，开口宽二寸半。
足太阳膀胱经的脉气，起始于目内眦（睛明穴），向上到达额部，交会于头顶。它的支脉，从头顶进入联络脑部，再复出分别下行至项部，沿着肩部内侧夹着脊柱，抵达腰部中，深入循行于骶部，联络肾脏，归属于膀胱。它的另一支脉，从腰部向下，夹着脊柱，穿过臀部，进入腘窝中（委中穴）。它的又一支脉，从腘窝内侧左右分出，向下穿过肩胛，夹着脊柱，向内经过髋关节（髀枢），沿着大腿外侧后缘向下，在腘窝中汇合，再向下穿过小腿肚（腨肠）内侧，出于外踝后方，沿着京骨穴到达小趾外侧端。
足太阳膀胱经的脉气，从目内眦上起，到达额尖。分支从头顶上行至耳角，直行者从头顶脑后悬垂而下，联络脑部，复出分别下行至项部，仍沿着肩膊夹着脊柱边缘，抵达腰部的骶部和肾脏、膀胱内部，其中一支向下与前后阴相连。穿过臀部斜入委中穴，另一支从臂部内侧左右分出，穿过肩胛夹着脊柱经过髋关节，在小腿内侧后缘与腘窝中汇合，向下穿过小腿肚内外侧及外踝后方，在京骨骨下到达小趾外侧。
【注释】足太阳膀胱经的脉气，起始于目内眦的睛明穴，从睛明穴循行经过攒竹、曲差穴，上达额部交会于头顶，进入承光穴，从承光穴循行经过通天穴。它的支脉，从头顶上行至耳上角，与足少阳胆经相交。它的直行者，从通天穴深入联络于大杼穴，从大杼穴循行经过肩胛内侧的风门穴，从风门穴循行经过肺俞穴，夹着脊柱抵达腰部中的厥阴俞穴，从厥阴俞穴循行经过心俞、膈俞、肝俞、胆俞、脾俞、胃俞、三焦俞，深入循行于骶部联络肾脏，从肾俞穴循行经过气海俞，从腰部向下夹着脊柱经过大肠俞穴，从大肠俞穴循行经过关元俞、膀胱俞、中膂俞、白环俞等穴，另外上行经过上髎、次髎、中髎、下髎等穴。它的支脉，又再次上行至肩膊内侧，从附分穴循行穿过肩胛到达魄户穴，从魄户穴循行夹着脊柱内侧经过膏肓、神堂、譩嘻、膈关、魂门、阳纲、意舍、胃仓、肓门、志室、胞肓等穴，经过髋关节的秩边穴，从秩边穴循行沿着大腿外侧后缘，经过承扶、浮郄、委阳穴，向下汇合于腘窝中的委中穴，从委中穴循行经过合阳穴，从合阳穴向下穿过小腿肚内部的承筋穴，从承筋穴循行经过承山、飞扬、附阳等穴，从附阳穴循行出于外踝后方的昆仑穴，从昆仑穴循行经过仆参、申脉、金门等穴，循行到京骨穴即本经的京骨穴，从京骨穴循行经过束骨、通谷穴，到达小趾外侧端的至阴穴结束，从而与足少阴肾经相交。
The medical classics state: The Bladder is the official of the "Zhou Du" (the reservoir where body fluids gather), storing the Jin Ye (body fluids); it can be excreted only through Qi transformation. It is also stated that the Bladder is located at the level of the nineteenth thoracic vertebra, situated below the Kidney and anterior to the Large Intestine. It has a lower opening but no upper opening. At the Shuifen (Water Separation) acupoint, one cun above the umbilicus, which serves as the lower opening of the Small Intestine and the upper boundary of the Bladder, fluids separate from the ileum and seep into the Bladder along with Qi movement. Both entry and exit depend on Qi transformation; if the entering Qi fails to transform, water flows into the Large Intestine, causing diarrhea. If the exiting Qi fails to transform, the lower orifices become obstructed, leading to strangury (difficulty in urination) or swelling. This meridian contains abundant blood but scarce Qi.
The *Nan Jing* (Classic of Difficult Issues) states: The Bladder weighs nine liang and two zhu, measures nine cun in length and width, holds nine sheng and nine he of urine, and its opening is two and a half cun wide.
The Foot-Taiyang Bladder Meridian originates at the inner canthus of the eye, ascends to the forehead, and intersects at the vertex. Its branch enters the brain from the vertex, emerges again, descends separately to the nape, follows the shoulder, runs internally alongside the spine, reaches the middle of the waist, enters the sacral region, connects with the Kidney, and belongs to the Bladder. Another branch descends from the waist, flanking the spine, passes through the buttocks, and enters the popliteal fossa. Yet another branch diverges from the medial side of the popliteal fossa, passes laterally through the scapula, flanks the spine, passes medially through the hip joint (bi shu), follows the posterior-lateral aspect of the thigh, converges in the popliteal fossa, descends through the calf muscle, emerges posterior to the lateral malleolus, follows the Jinggu point, and terminates at the lateral side of the little toe.
The Foot-Taiyang Bladder Meridian begins at the inner canthus, ascends to the tip of the forehead. A branch ascends from the vertex to the ear angle; the main trunk hangs down from the back of the head after the vertex, connects with the brain, emerges again, descends separately to the nape, still follows the shoulder blades flanking the spine, reaches the lumbar sacrum, Kidney, and Bladder internally, with one branch connecting downwards to the genital and anal regions. It penetrates the buttocks obliquely into the Weizhong acupoint. Another branch diverges from the medial arm, penetrates the scapula, flanks the spine, passes through the hip joint, converges in the popliteal fossa on the posterior-medial aspect of the leg, descends through the calf muscles and posterior to the malleoli, and reaches the lateral side of the little toe below the Jinggu bone.
[Note] The Foot-Taiyang Meridian originates at the Jingming acupoint at the inner canthus. From Jingming, it travels through Zanzhu and Qucha, ascends to the forehead to intersect at the vertex, enters the Chengguang acupoint, and from Chengguang travels through the Tongtian acupoint. Its branch ascends from the vertex to the upper corner of the ear, intersecting with the Foot-Shaoyang Gallbladder Meridian. The main trunk enters the Dazhu acupoint from Tongtian, travels from Dazhu through the Fengmen acupoint on the medial shoulder blade, from Fengmen through the Feishu acupoint, flanks the spine to reach the Jueyinshu acupoint in the waist, and from Jueyinshu travels through Xinshu, Geshu, Ganshu, Danshu, Pishu, Weishu, and Sanjiaoshu, enters the sacral region to connect with the Kidney, travels from Shenshu through Qihais hu, descends from the waist flanking the spine through Dachangshu, travels from Dachangshu through Guanyuanshu, Pangguangshu, Zhonglvs hu, Baihuanshu, and other points, and additionally ascends through Shangliao, Ciliao, Zhongliao, and Xialiao. Its branch ascends again to the medial shoulder blade, travels from Fufen through the Pohu acupoint penetrating the scapula, from Pohu flanks the spine internally through Gaohuang, Shen tang, Yixi, Ge Guan, Hunmen, Yanggang, Yishe, Weicang, Huangmen, Zhishi, Baohuang, and other points, passes through the Zhibian acupoint at the hip joint, from Zhibian follows the posterior-lateral aspect of the thigh through Chengfu, Fupi, and Weiyang, converges downwards into the Weizhong acupoint in the popliteal fossa, travels from Weizhong through Heyang, descends through Chengjin inside the calf, from Chengjin travels through Chengshan, Feiyang, and Fuyang, emerges from Fuyang posterior to the lateral malleolus at the Kunlun acupoint, from Kunlun travels through Buzhen, Shenmai, and Jinmen, follows the Jinggu acupoint (Jinggu of this meridian), from Jinggu travels through Shugu and Tonggu, and terminates at the Zhiyin acupoint on the lateral side of the little toe, thereby intersecting with the Foot-Shaoyin Kidney Meridian.