Final answer:
The inferior border of the inguinal triangle is formed by the inferior epigastric vessels.
Step-by-step explanation:
The inferior border of the inguinal triangle, which is also known as Hesselbach's triangle, is formed by the inferior epigastric vessels. Specifically, it is the line running from the vessels where they curve from the lateral margin of the rectus abdominis muscle to where they enter the rectus sheath.
The inguinal triangle is of clinical significance because it is an area where inguinal hernias can occur. The other boundaries of the inguinal triangle include the lateral border formed by the inferior epigastric vessels and the medial border which is the edge of the rectus abdominis muscle.