The lymphatic system functions to drain tissue fluid, plasma proteins and other cellular debris back into the blood stream. Once this collection of substances enters the lymphatic vessels it is known as lymph. This then reaches lymph nodes which filter and is directed into the venous system.
Most of the lymph from the lower limb drains into the inguinal lymph nodes. Mostly it happens directly but it could partly occur through the popliteal and anterior tibial nodes. The deep structures of the gluteal region and the upper part of the back of the thigh drain into the internal iliac nodes along the gluteal vessels.
Superficial Inguinal Lymph Nodes
Superficial lymph nodes drain the skin and fasciae of the lower limb, the perineum and the trunk below the umbilical plane. They are divided into three sets.
Efferents from all superficial inguinal nodes pierce the cribriform fascia, and terminate in the deep inguinal nodes. A few may pass directly to the external iliac nodes.
Superficial inguinal lymph nodes are arranged in following groups
Lower Vertical Group
It is placed along both sides of the terminal part of the great saphenous vein, and contains about 4 or 5 nodes. They drain the skin and fasciae of the lower limb except the buttock and except the short saphenous territory. A few lymphatics, accompanying the short saphenous vein, cross the leg, accompany the great saphenous vein, and drain into this group of nodes.
Upper Lateral Group
It is placed below the lateral part of the inguinal ligament, and contains about 2 or 3 nodes. They drain the skin and fasciae of the upper part of the lateral side of the thigh the buttock, the flank and the back below the umbilical plane.
Upper Medial Group
It is placed below the medial end of the inguinal ligament along the course of the superficial epigastric vessels. The group contains 2 to 3 nodes which drain
- Anterior abdominal wall below the level of the umbilicus
- Perineum, including the external genitalia (except the glans)
- Anal canal below the pectinate line
- Vagina below the hymen
- Penile part of the male urethra
- Superolateral angle of the uterus ( via the round ligament)
Deep Inguinal Lymph Nodes
These are about 4 to 5 in number, and lie medial to the upper part of the femoral vein. The most proximal node of this group (gland of Cloquet or lymph node of Rosenmuller) lies in the femoral canal.
These nodes receive afferents from: (a) the superficial inguinal nodes; (c) glans penis or clitoris; and (d) the deep lymphatics of the lower limb accompanying the femoral vessels.
Popliteal Lymph Nodes
These nodes lie near the termination of the small saphenous vein, deep to the deep fascia. One node lies between the popliteal artery and the oblique popliteal ligament.
They receive affrents from
- Territory of the small saphenous vein
- Deep parts of the leg
- Knee joint.
Their efferents run along the popliteal and femoral lymphatic vessels, and terminate in the deep inguinal nodes.
Anterior Tibial Lymph Node
One inconstant node may lie along the upper part of the anterior tibial artery. When present, it collects lymph from the anterior compartment of the leg, and passes it on to the popliteal nodes.
Superficial lymph vessels are larger and are in greater number than the deep lymphatics.
They run in the superficial fascia and ultimately from two streams.
- The main stream follows the great saphenous vein, and ends in the lower vertical group of superficial inguinal lymph nodes.
- The accessory stream follows the small saphenous vein, and ends in the popliteal lymph nodes.
These are smaller and fewer than the superficial lymphatics. They are responsible for draining all the structures lying deep to the deep fascia. They run along the principal blood vessels, and terminate mostly into the deep inguinal nodes, either directly or indirectly through the popliteal nodes.
The deep lymphatics from the gluteal region and from the upper part of the back of the thigh accompany the gluteal vessels and end in the internal iliac nodes.
Lymphatics obstruction caused by the parasite filarial is very common in the lower limb results in great hypertrophy of the skin and of subcutaneous tissue (elephantiasis).
Lymph Node Enlargement
The commonest cause of a swelling in the subinguinal area is enlargement of the inguinal lymph nodes. This can be caused by infection, or carcinomia, anywhere in the area drained by these nodes.