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the inguinal ligament it enters the middle compartment of the femoral sheath, through which it ascends to its termination, lying between the compartment for the femoral artery on the lateral side and the femoral canal on the medial side.

It usually contains two bicuspid valves—one near its termination and the other just proximal to the entrance of its profunda tributary.

Tributaries. — It receives tributaries which correspond with the branches of the femoral artery and the larger of the two superficial veins of the lower extremity, viz., the great saphenous vein, which enters the femoral vein where that vessel lies in the middle

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compartment of the femoral sheath, and, not uncommonly, it is joined by the medial and lateral circumflex veins.

Vena Iliaca Externa.—The external iliac vein (Figs. 773, 774, and 777) is the upward continuation of the femoral vein. It commences, on the medial side of the termination of the external iliac artery, immediately posterior to the inguinal ligament, and ascends, along the aperture of the pelvis minor, to a point opposite the sacro-iliac joint, and at the level of the lumbo-sacral articulation, where it ends, immediately behind the hypogastric artery, by joining the hypogastric vein to form the common iliac vein. It lies, at first, on the medial side of the external iliac artery, but on a somewhat posterior plane, and then directly posterior to the artery, whilst just before its termination it crosses the lateral side of the hypogastric artery, and separates that vessel from the medial border of the psoas major muscle. In its whole course the vein lies anterior to the obturator nerve. It is usually provided with one bicuspid valve; sometimes there are two, but both

are usually incompetent. Its tributaries correspond to the branches of the external iliac artery; that is, the deep circumflex iliac and inferior epigastric veins open into it, close to its com

mencement, whilst, in addition, it freSuperficial epigastric vein quently receives the pubic vein. iliac vein

The pubic vein forms a communicaSuperficial external pudendal vein

tion between the obturator vein and the Femoral vein

external iliac vein. It varies in size, Great saphenous vein and may form the main termination of

the obturator vein, from which it arises. Lateral superficial femoral vein

Commencing in the obturator canal,

it ascends, along the pubic branch of Medial superficial femoral vein

the inferior epigastric artery, to reach the external iliac vein.

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THE SUPERFICIAL VEINS OF THE

INFERIOR EXTREMITY.

The superficial veins of the lower limb terminate in two trunks, one of which, the small saphenous vein, passes from the foot to the popliteal space;

whilst the other, the great saphenous vein, Great saphenous vein

extends from the foot to the groin.

The superficial veins of the sole of the foot form a fine plexus, immediately under cover of the skin, from which anterior, medial, and lateral efferents pass. The anterior efferents terminate in a transverse arch which lies in the furrow at the roots of the toes, and the medial and lateral efferents pass round the sides of the foot to the great or small saphenous' veins. The transverse arch receives also small plantar digital veins from the toes, and it communicates by intercapitular veins with the veins on the

dorsum of the foot. Great saphenous vein

The superficial veins on the dorsal aspect of each toe unite to form two dorsal special digital veins, which run

along the borders of the dorsal surface. Dorsal venous arch The special dorsal digital veins of the

adjacent borders of the interdigital clefts unite, at the apices of the clefts, to form four dorsal metatarsal veins which ter

minate in the dorsal venous arch. The Fig. 794. – THE GREAT SAPHENOUS VEIN AND ITS

dorsal digital vein from the medial side of TRIBUTARIES.

the great toe ends in the great, and that from the lateral side of the little toe in the small saphenous vein.

Arcus Venosus Dorsalis Pedis.—The dorsal venous arch lies in the subcutaneous tissue, between the skin and the dorsal digital branches of the superficial peronæal nerve, opposite the anterior parts of the bodies of the metatarsal bones. "It ends, medially, by uniting with the medial dorsal digital vein of the great toe to form

the great saphenous vein, and laterally by joining the lateral dorsal digital vein of the little toe to form the small saphenous vein. The dorsal venous arch receives the dorsal metatarsal veins; interdigital efferents from the plantar transverse arch; and numerous tributaries from the dorsum of the foot, which anastomose freely together forming a wide-meshed dorsal venous plexus, open into it posteriorly.

Vona Saphena Magna.—The great saphenous vein is formed by the union of the medial extremity of the dorsal venous arch with the medial dorsal digital vein of the great toe. It passes anterior to the medial malleolus, crosses the medial surface of the distal third of the body of the tibia, and ascends, immediately posterior to the medial margin of the tibia, to the knee, where it lies just posterior to the medial condyle of the femur; continuing proximally, with an inclination forwards and laterally, it gains the proximal part of the femoral tri

saphenous gone, where it perforates the fascia cribrosa and the femoral sheath to reach its termination in the femoral vein. In the foot and leg it is accompanied by the saphenous nerve, and for a short distance distal to the knee by the superficial or saphenous branch of the arteria genu suprema. In the thigh, branches of the medial cutaneous nerve (0.T. internal) lie in close relation with it. It contains from eight to twenty bicuspid valves.

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Small

Tributaries. — It communicates freely, through the deep fascia, with the deep intermuscular veins. In the foot, it receives tributaries from the medial part of the sole and from the dorsal venous plexus. In the leg it is joined by tributaries from the dorsum of the foot, the medial and posterior parts of the heel, the front of the leg and the back of the calf, and it anastomoses freely with the small saphenous vein. In the thigh it receives numerous tributaries, and

Lateral end of amongst them are two superficial femoral veins.

dorsal venous Of these, the lateral ascends from the lateral

arch side of the knee and terminates in the great saphenous vein at the distal part of the femoral trigone ; the other, the medial, ascends from the posterior aspect of the thigh, along its medial side, and terminates in the great saphenous vein near the fossa ovalis. In many cases the medial Fig. 795.—THE SMALL SAPHENOUS VEIN superficial femoral vein communicates distally

AND ITS TRIBUTARIES. with the small saphenous vein, and when that condition exists the medial superficial femoral vein is called the accessory saphenous vein. The last tributaries to enter the great saphenous vein are the superficial circumflex iliac, superficial epigastric, and superficial external pudendal veins. They accompany the corresponding arteries, and terminate in the great saphenous vein immediately before it perforates the fascia cribrosa.

The superficial circumflex iliac vein receives blood from the lower and lateral part of the abdominal wall and the proximal and lateral parts of the thigh. The superficial epigastric vein drains the lower and medial part of the abdominal wall, and the superficial external pudendal vein receives blood from the dorsum of the penis and the scrotum in the male, and from the labium majus in the female.

Vena Saphena Parva.-The small saphenous vein is formed by the union of the lateral extremity of the dorsal venous arch with the lateral dorsal digital vein of the little toe. At first it passes posteriorly, along the lateral side of the foot and distal to the lateral malleolus, lying on the peronæal retinacula (O.T. ext. ann. lig.), in company with the nervus suralis; then it passes posterior to the lateral malleolus, and along the lateral border of the tendo calcaneus, still in company with the nervus suralis, to the middle of the calf, proximal to which it is continued in the superficial fascia, accompanied by the superficial sural artery, to the distal part of the popliteal fossa, where it pierces the deep fascia, and terminates in the popliteal vein. It communicates, round the medial side of the leg, with the great saphenous vein, and through the deep fascia with the deep veins, and it contains from six to twelve bicuspid valves.

Tributaries.—It receives tributaries from the lateral side of the foot, the lateral side and back of the heel, the back of the leg, and, occasionally, a descending tributary from the back of the thigh. Just before it pierces the popliteal fascia it frequently gives off a small branch which ascends round the medial side of the thigh and unites with the medial superficial femoral vein to form the accessory saphenous vein. In that way a communication is established between the great and small saphenous veins, which may become enlarged, and constitute the main continuation of the small saphenous vein.

THE PORTAL SYSTEM. The veins which form the portal system are the portal, the superior and inferior mesenteric and the splenic veins and their tributaries. They convey blood to the liver—(1) from almost the whole of the abdominal and pelvic parts of the alimentary canal, (2) from the pancreas, and (3) from the spleen. The tributaries of origin correspond closely with the terminal branches of the splenic, and the superior and inferior mesenteric arteries, after which they are named and which they accompany for a considerable distance. The larger or terminal veins, however, leave their associated arteries; the inferior mesenteric vein joins the splenic vein, and the latter unites with the superior mesenteric vein to form the portal vein, which passes to the liver. All the larger vessels of this system are devoid of valves, but valves are present in the tributaries.

Vena Porta.—The portal vein is a wide venous channel, about 75 mm. (three inches) long, which conveys blood from the stomach, from the whole of the intestine, except the terminal portion of the rectum, and from the spleen and pancreas to the liver. Unlike other veins, it ends like an artery, by breaking up into branches which ultimately terminate in capillaries in the substance of the liver ; from the capillaries, which also receive the blood conveyed to the liver by the hepatic artery, the hepatic veins arise; and, as the hepatic veins open into the inferior vena cava, the portal blood ultimately reaches the general systemic circulation.

The portal vein commences by the union of the superior mesenteric and the splenic veins, posterior and to the left of the neck of the pancreas, and either anterior to the left border of the inferior vena cava, at the level of the body of the second lumbar vertebra, or in front of the upturned extremity of the processus uncinatus of the head of the pancreas. It ascends, anterior to the inferior vena cava and posterior to the neck of the pancreas and the first part of the duodenum, to the lower border of the epiploic foramen (Winslow), where it passes forwards, in the right gastro-pancreatic fold of peritoneum, and enters the lower border of the gastro-hepatic ligament. Continuing its' upward course, it lies posterior to the bile-duct and hepatic artery, and anterior to the epiploic foramen (Winslow); it ultimately reaches the right end of the porta hepatis, where it ends by dividing into a short and wide right and a longer and narrower left branch. Just before its termination it enlarges, forming the sinus of the portal vein.

The right branch generally receives the cystic vein and then enters the right lobe of the liver, in which it breaks up into numerous branches which terminate in the portal capillaries around the periphery and in the substance of the liver lobules.

The left branch runs from right to left, along the porta hepatis, giving off branches to the caudate and quadrate lobes; it crosses the umbilical fossa, and ends in the same manner as the right branch, but in the substance of the left lobe of the liver.

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As it crosses the umbilical fossa, the left branch of the portal vein is joined, anteriorly, by the round ligament of the liver and some small veins, and, posteriorly, by the ligamentum venosum. The round ligament is a fibrous cord which passes from the umbilicus to the left branch of the portal vein. It represents the remains of the left umbilical vein of the fætus. The small veins which accompany it connect the left branch of the portal vein with the superficial veins round the umbilicus. The ligament venosum connects the left branch of the portal vein with the upper part of the inferior vena cava. It is the remains of a fotal blood

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THE

Fig. 796.-SCHEMA OF THE PORTAL SYSTEM OF VEINS AND ITS CONNECTIONS WITH SYSTEMIC

SYSTEM.—It must be remembered that systemic blood carried by the hepatic artery also enters the liver capillaries, therefore the hepatic veins contain both portal and systemic blood.

vessel, the ductus venosus, through which blood, carried from the placenta by the left umbilical vein, passed to the inferior vena cava without going through the liver.

The portal vein is accompanied by numerous lymph vessels, and it is surrounded, in the lesser omentum, by filaments of the hepatic plexus of nerves.

Tributaries.—Soon after its formation the portal vein receives the coronary and right gastric veins, and the cystic vein opens into its right branch.

Vena Coronaria Ventriculi.—The coronary vein commences in the lesser omentum by the union of tributaries from both surfaces of the stomach. It runs to the left

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