Anatomy At a Glance by unknow

Author:unknow
Language: eng
Format: mobi
Tags: anatomy, glance

Fig.43.1

The superficial veins and lymphatics of the lower limb. The arrows indicate the direction of lymph flow

Vein linking great and small saphenous veins

Popliteal lymph nodes

Short saphenous vein

Superficial epigastric Inguinal ligament Pubic tubercle ym- Edge of saphenous opening ^^ Femoral vein

^- Deep fascia of thigh

Superficial external pudendal

Great saphenous vein

Fig.43.2

The termination of the great saphenous vein

Fig.43.3

Lymphoedemaof the lower limb

The superficial veins of ttie lower limb (Fig. 43.i)

The superficial system comprises tlie great and small saphenous veins. Tliese are of utmost clinical importance as they are predisposed towards becoming varicose and consequently often require surgery. They are also the commonly used conduits for coronary artery surgery.

• The great saphenous vein arises from the medial end of the dorsal venous network on the foot. It passes anterior to the medial malleolus, along the anteromedial aspect of the calf (with the saphenous nerve), migrates posteriorly to a handbreadth behind patella at the knee and then courses forward to ascend the anteromedial thigh. It pierces the cribriform fascia to drain into the femoral vein at the saphenous opening. The terminal part of the great saphenous vein usually receives superficial tributaries from the external genitalia and the lower abdominal wall (Fig. 43.2). At surgery these help to distinguish the saphenous from the femoral vein as the only tributary draining into the latter is the saphenous vein. Anteromedial and posterolateral femoral {lateral accessory) tributaries, from the medial and lateral aspects of the thigh, also sometimes drain into the great saphenous vein below the saphenous opening.

The great saphenous vein is connected to the deep venous system at multiple levels by perforating veins. These usually occur above and below the medial malleolus, in the gaiter area, in the mid-calf region, below the knee and one long connection in the lower thigh. The valves in the perforators are directed inwards so that blood flows from superficial to deep systems from where it can be pumped upwards assisted by the muscular contractions of the calf muscles. The deep system is consequently at higher pressure than the superficial and thus, should the valves in the perforators become incompetent, the increased pressure is transmitted to the superficial system and these veins become varicose.

• The small saphenous vein arises from the lateral end of the dorsal venous network on the foot. It passes behind the lateral malleolus and over the back of the calf to pierce the deep fascia in an inconstant position to drain into the popliteal vein.

The deep veins of the lower limb

The deep veins of the calf are the venae comitantes of the anterior and posterior tibial arteries which go on to become the popliteal and femoral veins. The deep veins form an extensive network within the

posterior compartment of the calf—the soleal plexus from which blood is assisted upwards against gravitational forces by muscular contraction during exercise. Failure of this 'muscle pump' to work efficiently, as occurs, for instance, during long flights in cramped conditions, may cause deep venous thrombosis (DVT).

Varicose veins

These are classified as:

• Primary: due to inherent valve dysfunction.

• Secondary: due to impedance of flow within the deep venous circulation.

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