The femoral sheath (crural sheath) is formed by a prolongation downward, behind the inguinal ligament, of the fasciæ which line the abdomen, the transversalis fascia being continued down in front of the femoral vessels and the iliac fascia behind them.

The sheath assumes the form of a short funnel, the wide end of which is directed upward, while the lower, narrow end fuses with the fascial investment of the vessels, about 4 cm. below the inguinal ligament.

It is strengthened in front by a band termed the deep crural arch.

The lateral wall of the sheath is vertical and is perforated by the lumboinguinal nerve; the medial wall is directed obliquely downward and lateralward, and is pierced by the great saphenous vein and by some lymphatic vessels.

The sheath is divided by two vertical partitions which stretch between its anterior and posterior walls.

The lateral compartment contains the femoral artery, and the intermediate the femoral vein, while the medial and smallest compartment is named the femoral canal, and contains some lymphatic vessels and a lymph gland imbedded in a small amount of areolar tissue.