Before we look at the muscles, there’s one important structure that we need to add to the picture: the inguinal ligament. Here’s the inguinal ligament. It’s a strong band of tendinous tissue, that goes from the anterior superior iliac spine, to the pubic tubercle.
There’s a gap between the inguinal ligament, and the underlying bone. Through this gap some important structures pass from the abdomen, to the thigh, including the femoral vein, artery and nerve medially; and the belly of the psoas and iliacus muscles laterally.
The inguinal ligament isn’t an isolated structure. As we’ll see, it’s the lowest part of the external oblique aponeurosis, which is the outermost of the muscular and tendinous layers of the anterior abdominal wall.