Normal anatomy

The aorta and peripheral arteries

The thoracic and the abdominal aorta and its branches are schematically depicted in Fig. 6.

The ascending thoracic aorta originates at the annulus of the aortic valve and gives off the right and left coronary artery. The aorta ascends towards the right and swings approximately at the level of the 5th thoracic vertebra in an arch-like curve (aortic arch) posteriorly to descend to the left of the vertebral column (descending aorta). From the aortic arch the neck vessels originate in the order right brachiocephalic trunk (which bifurcates into the right subclavian and right common carotid artery), left common carotid artery and left subclavian artery. The aorta has three main points of fixation: At the level of the aortic valve, the brachiocephalic vessels and ligamentum arteriosum and at the diaphragmatic hiatus. The descending aorta is the direct continuation of the aortic arch distally beyond the origin of the left subclavian artery and gives off the intercostal arteries in pairs before penetrating the diaphragm through the hiatus to become the abdominal aorta.

The first anterior branch of the abdominal aorta is at the level of about T 12 to LI. This is the celiac trunk which divides into the left gastric, the splenic and common hepatic artery. About one centimetre lower than the celiac trunk is the origin of the superior mesenteric artery and the right and left renal arteries arise, another one to two centimetres caudally. At the level of L3 to L4 the inferior mesenteric artery originates anterolaterally to the left. Other important branches are the paired lumbar arteries. The aorta then bifurcates at L4 to L5 into the right and left common iliac arteries which divide into the internal and external iliac arteries. The internal iliac artery commonly divides into an anterior division (giving off the inferior gluteal and obturator artery and the internal pudendal and visceral artery to the urogenital organs) and the posterior division (iliolumbar and superior gluteal arteries). At the level of the inguinal ligament the external iliac artery becomes the common femoral artery which bifurcates into the superficial and deep femoral artery.

The superficial femoral artery after passing through the adductor hiatus becomes the popliteal artery which trifurcates below the knee into the anterior tibial artery and the tibioperoneal trunk which divides into the peroneal and posterior tibial arteries. The anterior tibial artery which runs in the anterior muscular compartment through the interosseous membrane ends distally in the dorsalis pedis artery. The posterior tibial artery supplies the plantar aspect of the foot.

In the upper extremities the blood supply originates in the right and left subclavian artery which give origin to the vertebral arteries on each side. Other branches of the subclavian artery are the thyreocervical trunk, the internal mammary artery and the costocervical trunk. At the lateral end of the first rib the subclavian artery becomes the axillary artery which becomes the brachial artery laterally to the teres major muscle. The brachial artery gives off the profunda brachii artery and bifurcates in the region of the elbow into the radial and ulnar arteries. The latter also gives origin to the interosseous artery. In the hand the radial artery forms the
deep and the ulnar artery the superficial palmar arch.

The vena cava and peripheral veins

The veins of the lower extremity and the vena cava are depicted schematically in fig. 7. In the lower extremity, the venous anatomy can be divided into foot vein, the superficial and the deep axial system, and the perforating (communicating) veins.

The veins of the foot are characterized by two plantar and two dorsal toe veins merging into the dorsal metatarsal veins, which then unite and form the superficial dorsal venous arch. This arch proceeds in a medial direction and flows into the long saphenous vein anterior to the medial malleolus. The lateral extension of the dorsal arch joins the short saphenous vein which in turn merges with the popliteal vein. Foot vein valves are, contrary to the situation proximally, directed towards the saphenous system.

The veins of the sole comprise a plantar cutaneous arch draining into lateral and medial marginal veins and from there into the short and long saphenous systems. The deep plantar veins arise at the fourth metatarsal system and at the medial malleolus join the posterior tibial veins. These deep plantar veins have a large central plexus, which has a capacity in excess of that needed to drain the foot, and have not got a recognized function. There are numerous valveless communicating veins between the major foot veins. The dorsal foot vein is an extension of the anterior tibial vein.

The superficial veins
The great saphenous vein forms in front of the medial malleolus by union of the medial marginal vein and the dorsal superficial arch. It runs in the superficial fascia on the medial side of the leg up to the knee and then behind the femoral condyles and again medially in the thigh. In the groin, it courses deeply to join with the femoral vein at the foramen ovale. Venous valves are numerous in this vein, and almost invariably there is a valve at the junction with the femoral vein.

The short saphenous vein starts behind the lateral malleolus, runs back towards the posterior midline, piercing the fascia relatively low in the calf and usually joins the popliteal vein. However, in one-third of cases it may also continue up the thigh to join with the deep femoral vein, the iliac system, or it may join the great saphenous or a gastrocnemius vein at the popliteal level of the knee.

Figure 7. Schematic drawing of the left pelvic and lower extremity veins. The deep leg veins from the level of the popliteal vein are paired (not shown). The gastrocnemius veins are paired and duplicated; there are several soleal veins.

The deep veins (Fig. 7)
Two posterior tibial, two peroneal and two thin anterior tibial veins possess many valves. They run along the corresponding arteries as venae comitantes in the muscular compartments of the leg. They join the popliteal vein at the lower popliteal fossa. From the soleus muscles, short veins, sinusoids with rather narrow outlets and mostly no valves, join the deep calf veins. Two paired, gastrocnemius veins come from the corresponding muscle bodies to join with the popliteal vein. They are usually smaller than the sinusoids and contain valves. The popliteal vein is usually single and lies under the nerve but superficial to the artery in the popliteal fossa. It continues medially upwards through the adductor hiatus and becomes the superficial femoral vein in the adductor canal. In the femoral canal, the superficial femoral vein contains 1-3 valves and receives the deep femoral vein to form the common femoral vein. Usually there is a valve at the origin of both of these veins before they merge. The common femoral vein passes medial to the artery and nerve under the inguinal ligament and becomes the external iliac vein. In two thirds of cases, a valve is se en in the common femoral vein. It receives the great saphenous vein medially.

Communicating veins
More than a hundred communicating veins, often called perforators, traverse the deep fascia of the leg, linking the axial veins of the deep and superficial systems to one another. These veins are of functional importance

Figure 8. Some perforating vein groups important for surgical treatment of venous insufficiency, seen from behind. (Dodd's group are venae comm. fem. med. intermedia, Boyd's are the vv. comm. cruris intermed., and Cockett's group empty into a vein of the vv. tib. post.). The levels of two dorsal perforators are also indicated, the upper communicating with a gastrocnemius vein.

since incompetence will lead to bidirectional flow, local cutaneous venous hypertension, and varicosities (Fig. 8).

Pelvic veins
The valveless external iliac veins join the internal iliacveins to form the common iliac vein. In thrombotic occlusion of the external iliac vein, collateral vessels may arise from the internal pudendal vein and rectal vein plexus into the internal iliac. In mesenteric vein hypertension collateral flow may occur in the opposite direction. Collaterals may also form via epigastric veins to the internal mammary vein, or par-umbilical veins in the abdominal wall.

The inferior vena cava
The inferior vena cava forms in front of the fifth lumbar vertebra by union of the two common iliac veins. It receives segmental, small lumbar veins draining the muscles and skin of the back. The ascending lumbar veins, ending in the azygous vein on the right side and in the hemiazygous vein on the left, form an anastomosis between the common iliac vein and the lumbar veins. This is an important collateral route of circulation between the inferior and superior vena cava. The right testicular vein arises from the pampiniform plexus and empties into the vena cava, while the left testicular vein drains into the left renal vein. In the female, the two ovarian veins have similar courses parallel to the cava.

The right renal vein is shorter and thicker than the left, the latter receives the left testicular and suprarenal veins and crosses in front of the aorta to join the inferior vena cava. The short, right suprarenal vein plugs directly into the cava.

The inferior vena cava is situated to the right of the aorta, in front of the vertebral column. From the renal level, it proceeds upwards slightly to the right. It receives 2-3 short, but large hepatic veins just before piercing the diaphragm at the caval hiatus and ending in the right atrium.

Veins of the upper extremity and the shoulder
The deep veins of the arms follow the arteries as subfascial venae comitantes. They are paired and possess multiple anastomoses. The proximal brachial vein, the axillary and the subclavian vein are unpaired.

The larger subcutaneous veins may show considerable variations. They start with the basilic vein on the dorsal ulnar side of the lower arm, and the cephalic vein on the radial side. They proceed upwards to the front of the arm. In the cubital fossa these two veins are connected by the ulnar/proximal median cubital vein. If a median brachial vein is present, it will divide into a median cephalic and a median basilic vein in the cubital fossa, replacing the median cubital vein. The basilic vein proceeds in the medial bicipital cleft, then turns through the fascia into the depth to join with the axillary vein. The cephalic vein runs on the lateral side of the upper arm, in the lateral bicipital cleft, then between the deltoid and lateral pectoral muscle, passes under the clavicle and descends to empty into the axillary vein. The subclavian vein proceeds in front of the scalene muscle to join with the internal jugular vein forming the brachiocephalic vein.

The thoracoepigastric veins and the lateral thoracic vein both drain into the axillary vein and are collateral pathways for abdominal wall veins and the 6-7 upper intercostal spaces, respectively.

Christoph L. Zollikofer and Frode Laerum