VEINS OF THE LOWER EXTREMITY 683 



The plexus is surrounded by a kind of capsule formed by the superior fascia of the pelvic 

 diaphragm. It terminates in a single stem on each side which opens into the hypogastric 

 vein. 



In the female the smaller pudendal plexus surrounds the urethra and receives the dorsal 

 and deep veins of the clitoris [vv. dorsales et profunda} clitoridis], veins from the vestibule, and 

 the posterior labial veins [vv. labiales posteriores]. It communicates freely with the utero- 

 vaginal plexus and is drained by the hypogastric veins. 



The vesical plexus [plexus vesicalis] surrounds the apex, the sides, and the anterior and 

 posterior surfaces of the bladder. It is situated between the muscular coat and the peritoneum, 

 and where the bladder is uncovered by peritoneum external to the muscular coat in the pelvic 

 cellular tissue. It opens into the pudendal plexus. 



The utero-vaginal plexus [plexus uterovaginalis] connects with the hemorrhoidal, vesical, 

 and uterine plexuses. Its lower part drains through the internal pudendal veins and the 

 pudendal plexus, and its upper protion largely through the ovarian veins, and partly through 

 the uterine veins [vv. uterinse] to the hypogastric (fig. 530). 



The haemorrhoidal plexus [plexus hsemorrhoidalis] surrounds the rectum, and is situated at 

 the lower part of that tube. It consists of two portions, one of which, the internal haemor- 

 rhoidal plexus, is situated between the muscular and mucous coats, while the other, the external 

 haemorrhoidal plexus, rests upon the outer surface of the muscular coat. The veins of this 

 latter plexus terminate in the inferior, middle, and superior haemorrhoidal veins. The inferior 

 [vv. haemorrhoidales inferiores] join the internal pudendal; the middle [v. haemorrhoidalis 

 media] accompanies the middle hasmorrhoidal artery and opens into the hypogastric and 

 superior haemorrhoidal veins; the superior (p. 678) forms the commencement of the inferior 

 mesenteric vein, and through this the blood gains the portal vein. None of these veins have 

 any valves, hence the enlargement of the inferior haemorrhoidal veins, when the portal vein is 

 obstructed, as in cirrhosis of the liver. Through the haemorrhoidal veins a free communication 

 is established between the systemic and portal system of veins. 



THE EXTERNAL ILIAC VEIN 



The external iliac vein [v. iliaca externa] (fig. 536), is the upward continuation 

 of the femoral. Beginning at the lower border of the inguinal ligament, it 

 accompanies the external iliac artery medially upward along the brim of the mi- 

 nor pelvis, lying at first on the superior ramus of the pubis, and then on the psoas 

 major muscle. It terminates by joining the hypogastric vein behind the hypo- 

 gastric artery, opposite the lower border of the sacro-iliac articulation, to form 

 the common iliac vein. It lies at first medial to the external iliac artery, and on 

 the left side remains medial to the artery throughout its course. On the right 

 side, however, as it ascends, it gradually gets behind the artery. It contains one or 

 two valves. 



In addition to the femoral, the external iliac receives the inferior epigastric 

 vein [v. epigastrica inferior] (fig. 536) and the deep circumflex iliac vein [v. cir- 

 cumflexa ilium profunda] (fig. 541), which accompany the arteries of the same 

 name. 



THE SUPERFICIAL VEINS OF THE ABDOMINAL WALL 



The plexus of superficial veins of the anterior abdominal wall is continuous 

 with that of the thorax (fig. 537). Its main channels are the superficial circumflex 

 iliac, the superficial epigastric, and the external pudendal, all of which open into 

 the great saphenous vein. These communicate, by means of subcutaneous 

 abdominal veins, with the superior epigastric vein, and, by means of the thoraco- 

 epigastric veins, with the lateral thoracic and costo-axillary. The superficial veins 

 communicate very freely with the deeper veins of the abdominal wall, and, by 

 means of parumbilical veins, they communicate to a slighter extent with the 

 portal system. 



The superficial veins of the lumbar region form an abundant plexus which 

 drains through the dorsal and lateral perforating branches of the intercostal, 

 lumbar, and sacral veins. 



THE VEINS OF THE LOWER EXTREMITY 



The veins of the lower extremity are divided into the superficial and the deep. 

 The superficial veins lie in the subcutaneous tissue superficial to the deep fascia, 

 through which they receive numerous communicating branches from the deep 

 veins. They are collected chiefly into two main trunks, which, beginning on the 

 foot, extend upward, one, the great saphenous, lying antero-medially, and the 



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