Inguinal anatomy.

The flat muscles of the anterior abdominal wall pass down well in front of the pectineal ligament of Astley Cooper on the summit of the superior pubic rumus, thus providing space for the spermatic cord and the great vessels of the lower limb to leave the abdomen. The abdominal wall layers turn back lower down to close the gap on the medial side of the external iliac vein. The external oblique aponeurosis turns back to form a strong inguinal ligament, and the attached fascia lata turns back as the lacunar ligament to meet and fuse with the pectineus muscle fascia 1-1.5 cm below Cooper's ligament. This leaves a deep trough, between Cooper's ligament behind and the posterior inguinal wall in front, which houses the transversely placed femoral canal. The transversalis fascia of the floor of the femoral canal turns down to form the medial wall of the venous compartment of the femoral sheath, and has the support of the curved edge of the lacunar ligament which effectively bars the femoral canal from entering the thigh. It is usually taught, however, that the lower end of the femoral canal passes unprotected into the thigh as the medial or third compartment of the femoral sheath, to lie between the femoral vein in its sheath and the curved edge of the lacunar ligament. If this were the case there would be no hindrance to the descent of a process of parietal peritoneum containing omentum or gut into and distending the femoral canal in the thigh. Would such a swelling, before the process of peritoneum had broken through the walls of the canal into the subcutaneous tissues of the groin, pass for a femoral hernia? Fortunately this problem does not arise. A study of the posterior aspect of the anterior abdominal wall, removed with the attached anterior half of the bony pelvis, reveals many details of the design and attachments of the deep inguinal ring, the femoral trough and canals and the femoral sheath.