KOMO 4 |Venous Disease Part 2: Venous Anatomy
8/7/06
VENOUS DISEASE Part 2: Venous Anatomy
By Mark Ombrellaro, MD
Since the vast majority of symptomatic vein disease involves the lower extremities, most of this discussion will focus on the legs. In the lower extremities, there are actually 3 "types" of veins that make up the anatomy of the venous system. The first and most important are the deep veins. The deep veins are the primary venous return circuit for the circulatory system. They are centrally located, deep within the leg, adjacent to the arteries, nerves, and bone. The various segments of the deep venous system are named in accordance with the adjacent artery. Starting at the ankle and working upwards, the major deep veins are called tibial veins. There are 3 pairs of tibial veins (for a total of 6) that begin in the region of the ankle and extend to the upper aspect of the calf. The posterior tibial veins begin around the inside aspect of the ankle, the anterior tibial veins being around the top of the foot, and the peroneal veins begin around the outer aspect of the ankle. In the calf region, the various pairs of tibial veins are joined by vein branches from the calf muscle itself. As the tibial veins come together, they form a single vein called the popliteal vein. The popliteal vein basically spans the knee joint, also including segments about a hands breadth above and below the joint as well. Next, as the popliteal vein passes through the thigh, it becomes known as the superficial femoral vein. In the area of the "Hip joint" or groin crease, the superficial femoral vein becomes the common femoral vein. After traversing the groin and entering the lower abdomen (or pelvis region) the common femoral vein becomes the external iliac vein, then the common iliac vein as it enters the upper pelvis (around the region of the "hip bones" or waistline). At the level of the umbilicus (belly button), the left and right common iliac veins (one from each leg) join together to form the vena cava: the major vein that returns blood from both legs and the internal structures of the abdomen and pelvis, back to the heart. The vena cava is located on the right side of the spine and is almost a straight continuation of the right common iliac vein. The left common iliac vein is actually longer than the right as it has to cross almost the entire pelvis in order to connect to the vena cava. This point will become important later on in our discussion.
In addition to the deep venous system, there is also the superficial venous system. The superficial venous system is exactly as its name implies, a more superficially located system of veins that includes the ones you often see under your skin. In people who have well developed muscles, these are the veins that are seen " popping out" but for the rest of us, large bulging superficially located veins are typically known as varicose veins. The superficial veins are located in the fatty tissue layer in between the muscle and the skin. In the lower extremity there are 2 major superficial venous channels, the greater saphenous vein (GSV) and the lesser saphenous vein (LSV). The greater saphenous vein is another vein that begins around the inner ankle. In fact if you look at the highest point of the "ankle bone" (the top of the mountain) the beginning of the greater saphenous vein can be characteristically found 1 finger breadth above, and another finger breadth in front of this point. The greater saphenous vein then continues in a straight line up the inside aspect of the leg, through the calf area, the knee, the thigh, and up to the groin. In the groin, the greater saphenous vein actually joins with the common femoral vein of the deep system. The greater saphenous vein is the vein that surgeons typically remove when one is needed for bypass procedures. After open heart bypass, leg bypass, or other arterial reconstructive procedures, that long scar down the inner part of the leg demonstrates the course of the greater saphenous vein. The lesser saphenous vein begins around the outside aspect of the ankle and crosses the back part of the leg, over the calf muscle and into the back part of the knee region. Behind the knee is where the superficial and deep venous systems also meet when the lesser saphenous vein connects with the popliteal vein. There are a multitude of other superficial veins in the leg, a few with names and most without. In general terms, think of the superficial venous system like 2 trees: the greater saphenous vein is the trunk of a large tree that spans the top and inner half of the leg, the lesser saphenous vein the trunk of a smaller tree primarily covering the back and outside part of the calf, and the other leg veins various branches of the 2 trees.
The third major category of veins are known as perforating veins (or perforators). These are branches that penetrate the muscles in various places, which also connect the superficial veins with the deep venous system. If you consider the venous system like a ladder, the deep system is one long leg, the superficial venous system the other, and the perforators are the cross bars. The path of blood flow within the venous system is from ankle upward toward the heart, as well as from the superficial system into the deep. The vast majority of venous return is therefore directed through the deep venous system.
More next week!
