The Inguinal Canal

The inguinal canal is the tubular structure that is located in the inguinal region, the lower portion of the anterior abdominal wall, with the pubic tubercle medially, the thigh inferiorly, and the anterior superior iliac spine superolaterally. It is about the 4cm long tube in the adult and extends from the deep inguinal ring to the superficial inguinal ring, which is a hole in the fascia transversalis downward to the superficial inguinal ring, a hole in the aponeurosis of the external oblique.

It lies immediately above and parallels to the inguinal ligament. In the newborn child's the deep inguinal ring lies posterior to the superficial ring but later it comes to the lateral side due to the growth. The inguinal canal is made up of:

1. Superficial and deep rings ( openings )
2. Anterior and superior walls
3. Floor and Roof ( inferior and superior walls )

• Deep Inguinal Ring: The deep inguinal ring is an oval opening that is present in the fascia transversalis, it lies about 1.3cm above inguinal ligament midway between the anterior superior iliac spine and the symphysis pubis. The inferior epigastric vessels are present medial to it, which pass upward from the external iliac vessels. The margins of the deep inguinal ring give attachment to the internal covering of the spermatic fascia.

• Superficial Ring: The superficial ring is a triangular shaped ring situated in the aponeurosis of the external oblique muscle that lies immediately above and medial to the pubic tubercle. The margins of the external oblique are called crura, which give attachment to the external covering of the spermatic cord.

Walls of the Inguinal Canal

• Anterior Wall: The anterior wall of the inguinal canal is formed by the aponeurosis of the external oblique muscle, which is reinforced laterally with the aid of the internal muscle. It lies opposite to the weakest part of the posterior wall, specifically, the deep inguinal ring.
• Posterior Wall:  It is formed by the conjoint tendon, and strengthen by the fascia transversalis laterally.
• Superior Wall:  Also known as the roof of the inguinal canal, it is formed by the transversalis fascia, internal oblique, and the transversus abdominis.
• Inferior Wall:    Also called floor of the inguinal canal, it is formed by the inguinal ligament and thickened by the lacunar ligament.

Functions of the Inguinal Canal

The inguinal canal permits structures of the spermatic cord to bypass to and away from the testes to the abdomen in the males, at the same time as in the females it acts as a passageway to pass the round ligament of the uterus from the uterus to the labium majus.

Nerve Supply

The inguinal canal is innervated by the ilioinguinal nerve a branch of the first lumbar nerve (L1). Note that the ilioinguinal nerve does no longer pass via the deep inguinal ring, and therefore it only travels through a part of the inguinal canal.