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1. How many venous systems take blood from the skin of the lower limb back to the trunk?
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Correct answer:
Two. These are the deep and superficial venous drainage systems.
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2. What is the deep venous system of the lower limb?
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Correct answer:
This comprises a network of veins lying deep to the deep fascia that envelopes the muscular compartments of the leg. Smaller tributaries drain into the popliteal vein behind the knee, which then ascends as the femoral vein to the inguinal ligament, where it becomes the external iliac vein. From there, blood passes up the common iliac vein, via the inferior vena cava, to the right atrium.
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3. What is the superficial venous system of the lower limb?
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Correct answer:
This comprises the medially placed great (long) saphenous vein, draining from the dorsum of the foot to the saphenofemoral junction in the groin, and the small (short) saphenous vein, which drains the lateral aspect of the lower limb into the popliteal vein behind the knee. The superficial system lies outside the deep fascia, and drains the skin and superficial tissues.
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4. What does the great saphenous vein drain?
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Correct answer:
This is medially placed; it drains the dorsum of the foot and joins the femoral vein at the saphenofemoral junction in the groin.
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5. What is the commonest cause of an intimal tear arterial injury? What happens when there is an intimal tear?
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Correct answer:
This drains the lateral aspect of the lower limb into the popliteal vein behind the knee.
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6. What are the perforating veins of the lower limb?
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Correct answer:
Besides the saphenofemoral and saphenopopliteal junctions, there are additional communications between superficial and deep veins with valves allowing blood in the superficial system to pass into the deep system, and preventing blood flowing out from the deep to superficial veins. These are called perforating veins, or perforators. Typically there is one mid-thigh (called the hunterian perforator on account of its relationship to Hunter’s canal), and several running up the medial and lateral aspect of the tibia just above the ankle.
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7. What is the name of the perforator found at mid-thigh level?
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Correct answer:
The hunterian perforator on account of its relationship to Hunter’s canal.
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8. What is the calf pump?
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Correct answer:
All the major leg veins have valves that prevent blood flowing away from the heart. As the calf muscles contract, the deep veins within them are squeezed and emptied, the blood passing upwards, directed towards the heart by non-return valves. As the muscles relax, blood flows in from the superficial system via perforators as well as from more distal segments of the vein, only to be pumped upwards again by the next contraction of the calf muscles, which are thus acting as a pump.
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9. What causes venous valves to become incompetent?
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Correct answer:
This haemodynamic disturbance is due either to a physical obstruction such as a thrombosis or to a functional obstruction leading to high pressure, as occurs when valves are incompetent or rarely when an arteriovenous fistula exists.
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10. What happens when a venous valve becomes incompetent?
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Correct answer:
When valves are incompetent there is greater resistance to return flow (the functional obstruction). One incompetent valve will put extra pressure on the next and will tend to make this incompetent; so once defects have arisen there is a tendency for the condition to get worse as further valves are involved.
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11. Which venous vessels have no valves?
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Correct answer:
There are no valves in the vena cava, and none in the common iliac vein.
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12. What is the definition of a varicose vein?
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Correct answer:
Varicose veins are abnormally dilated and lengthened superficial veins. They should be distinguished from prominent normal veins, which are most obvious over muscular calves of an athlete, and venous flare, the clusters of small dilated venules that occur subcutaneously as a result of hormonal change, pregnancy or trauma.
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13. What is venous flare? What causes it?
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Correct answer:
The clusters of small dilated venules that occur subcutaneously as a result of hormonal change, pregnancy or trauma.
