• short passage that extends inferiorly and medially through the inferior part of the abdominal wall.
• It is superior and parallel to the inguinal ligament.
• serves as a pathway by which structures can pass from the abdominal wall to the external genitalia.
• It is of clinical importance as a potential weakness in the abdominal wall, and thus a common site of herniation.

Boundaries

The inguinal canal is bordered by anterior, posterior, superior (roof) and inferior (floor) walls. It has two openings – the superficial and deep rings.

Walls

• Anterior wall – aponeurosis of the external oblique, reinforced by the internal oblique muscle laterally.
• Posterior wall – transversalis fascia.
• Roof – transversalis fascia, internal oblique, and transversus abdominis.
• Floor – inguinal ligament (a ‘rolled up’ portion of the external oblique aponeurosis), thickened medially by the lacunar ligament.

During periods of increased intra-abdominal pressure, the abdominal viscera are pushed into the posterior wall of the inguinal canal. To prevent herniation of viscera into the canal, the muscles of the anterior and posterior wall contract, and ‘clamp down’ on the canal.

Rings

The two openings to the inguinal canal are known as rings. There are two rings – deep (internal) and superficial (external):

• Deep (internal) ring:
  • Marks the internal opening of the inguinal canal
  • Found above the midpoint of the inguinal ligament (lateral to the epigastric vessels).
  • The ring is created by the transversalis fascia, which invaginates to form a covering of the contents of the inguinal canal.
• Superficial (external) ring:
  • Marks the external end of the inguinal canal
  • Lies just superior to the pubic tubercle.
  • It is a triangle shaped opening, formed by the invagination of the external oblique, which forms another covering of the inguinal canal contents.
  • It contains intercrural fibres, which run perpendicular to the aponeurosis of the external oblique and prevent the ring from widening.