Which structure forms the inguinal ligament?

The inguinal ligament is formed by the inferior border of the external oblique aponeurosis. This structure serves a significant role in the anatomy of the groin area as it runs from the anterior superior iliac spine (ASIS) to the pubic tubercle.

The external oblique muscle is involved in movements such as trunk rotation and lateral flexion, and its aponeurosis provides attachment points for other structures but is specifically the portion that contributes to the inguinal ligament. The integrity of this ligament is crucial for maintaining the pathway for structures that pass from the abdomen to the lower limb, including the inguinal canal.

Other structures mentioned, such as the transversalis fascia, internal oblique muscle, and rectus sheath, contribute to the broader anatomy of the abdominal wall and inguinal region, but they do not form the inguinal ligament specifically. The inguinal ligament's formation, primarily from the external oblique aponeurosis, highlights its importance in both structural support and facilitation of the passage of important vascular and neural structures in the region.