Now we’ll move on to look at the inguinal region. An important feature that we’ll see is a structure that passes obliquely through the abdominal wall, just above the inguinal ligament. In the female the structure is the round ligament of the uterus; in the male it’s the spermatic cord, the lifeline of the testis. The passage that this structure passes through is called the inguinal canal. We’ll start by taking a more detailed look at the inguinal ligament.
In this dissection, the body has been divided in the midline. Here’s the anterior superior iliac spine, here’s the pubic symphysis. Here’s the inguinal ligament. It’s the lowest part of the external oblique aponeurosis.
Laterally, the ligament is attached to the the anterior superior iliac spine. Medially, it’s attached to the pubic tubercle. The cut edge here was created by dividing the external oblique aponeurosis along this line.
The edge of the inguinal ligament can’t be seen from the outside because the fascia lata, the investing deep fascia of the thigh, is attached to the ligament along here.
To see the edge of the ligament we’ll go round to the inside. Here’s the edge of the ligament. The ilo-psoas fascia, which has been removed in this dissection, comes down over the iliopsoas, and is attached to the ligament along here.
The lowest fibers of the inguinal ligament curl around to form this triangular extension, the lacunar ligament. The lacunar ligament runs backwards and a little upwards, to insert on the sharp upper edge of the superior pubic ramus, the pecten.
Here’s transversus. Its lowest fibers arise from a thickening of the underlying ilio-psoas fascia.. Now we’ll add the internal oblique to the picture.
Here it is. The lowest fibers of the internal oblique arise from the same thickening of the ilio-psoas fascia. The tendinous fibers of these two muscles arch over and unite, to form this flat tendon, the conjoint tendon. The conjoint tendon is attached to the pubic crest, and also behind, to the pecten.
Now we’ll bring this lowest part of the external oblique aponeurosis up to its natural position, and add the rest of the aponeurosis to the picture. Here it is. There’s an opening in the external oblique aponeurosis, the superficial inguinal ring. Through this the spermatic cord (or the round ligament) passes as we’ll see shortly.
The fibers below and above the opening are called the inferior crus and the superior crus of the superficial inguinal ring. They’re attached to the pubic tubercle, and the pubic crest respectively.
The inguinal canal passes through the superficial inguinal ring, then beneath the free borders of the internal oblique muscle, and the transversus abdominis muscle.
To see where the inguinal canal begins, we'll go tround to the inside. It begins at this arch beneath the lower border of transversus, which is called the deep inguinal ring.