The Femoral Sheath and Femoral Canal

Key points

• • The femoral sheath is a downward funnel of abdominal fascia around the femoral artery and vein as they pass behind the inguinal ligament into the thigh.
• • It has three compartments: the artery laterally, the vein in the middle, and the femoral canal medially.
• • The femoral canal is the medial compartment; it contains fat and a lymph node and allows the femoral vein to expand when blood flow rises.
• • The upper opening of the canal is the femoral ring, bounded by the inguinal ligament in front, the lacunar ligament medially, the pubis behind and the femoral vein laterally.
• • The femoral nerve lies outside the sheath, on its lateral side, so it is not enclosed with the vessels.
• • A loop of bowel can push down through the narrow femoral canal as a femoral hernia, which lies below and lateral to the pubic tubercle and easily becomes trapped.