The fascia covering the psoas and iliacus is thin above, and becomes gradually thicker below as it approaches the inguinal ligament.
The portions of the fascia investing the iliacus (fascia iliaca) is connected, laterally to the whole length of the inner lip of the iliac crest; and medially, to the linea terminalis of the lesser pelvis, where it is continuous with the periosteum.
At the iliopectineal eminence it receives the tendon of insertion of the Psoas minor, when that muscle exists.
Lateral to the femoral vessels it is intimately connected to the posterior margin of the inguinal ligament, and is continuous with the transversalis fascia. Immediately lateral to the femoral vessels the iliac fascia is prolonged backward and medialward from the inguinal ligament as a band, the iliopectineal fascia, which is attached to the iliopectineal eminence.
This fascia divides the space between the inguinal ligament and the hip bone into two lacunæ or compartments, the medial of which transmits the femoral vessels, the lateral the Psoas major and Iliacus and the femoral nerve.
Medial to the vessels the iliac fascia is attached to the pectineal line behind the inguinal aponeurotic falx, where it is again continuous with the transversalis fascia.
On the thigh the fasciæ of the Iliacus and Psoas form a single sheet termed the iliopectineal fascia. Where the external iliac vessels pass into the thigh, the fascia descends behind them, forming the posterior wall of the femoral sheath. The portion of the iliopectineal fascia which passes behind the femoral vessels is also attached to the pectineal line beyond the limits of the attachment of the inguinal aponeurotic falx; at this part it is continuous with the pectineal fascia.
The external iliac vessels lie in front of the iliac fascia, but all the branches of the lumbar plexus are behind it; it is separated from the peritoneum by a quantity of loose areolar tissue.