The inguinal canal is a tubular opening that can be found on the anterior wall of the abdomen. It is placed at an angle and runs inferiorly and medially, which makes it an oblique canal and it is roughly three and a half to five centimeters in length. The inguinal ligament runs parallel and inferior to the canal and crosses it medially, very near its origin.
The Superficial and Deep Inguinal Rings
The inguinal rings superiorly and inferiorly limit the inguinal canal. They are the entrance and the exit to the tube.
The deep inguinal ring is the internal entrance to the inguinal canal, which is hidden behind the transversalis fascia. Clinically, it can be located exactly 1.25 centimeters above the midpoint of the inguinal ligament and is lateral to the epigastric vessels.
The superficial inguinal ring is the external exit of the inguinal canal. It sits behind the external oblique aponeurosis and is located superiorly and laterally to the pubic tubercle.
The superior border or the roof of the inguinal canal is made up of the medial crus of the aponeurosis of the external oblique muscle, the musculoaponeurotic arches of internal oblique muscle and the transverse abdominal muscles, as well as the transversalis fascia.
The inferior wall which acts as the floor of the canal and supports the inguinal structures contains the inguinal ligament, the lacunar ligament and the iliopubic tract.
The anterior border is covered by the aponeurosis of the external oblique muscle, the fleshy part of the internal oblique muscle and the superficial inguinal ring.
Lastly, the posterior border is contributed to by the transversalis fascia, the conjoint tendon, which is made up of the inguinal falx, the reflected part of the inguinal ligament and finally the deep inguinal ring.
The contents of the inguinal canal vary depending on the sex of the human in question. In males, the spermatic cord can be found, whereas in females, the round ligament of the uterus is present. The common structures that are included regardless of genitalia are the blood and lymphatic vessels and the ilioinguinal nerve. The surrounding structures that border the canal slightly collapse into any space created between the cannula structures so that nothing can enter the canal and become lodged there.
The clinical relevance of the inguinal canal is its relation to direct and indirect inguinal hernias. A hernia occurs when an organ, most commonly the small intestine, protrudes through the wall of a cavity that would normally contain it. A hernia of the inguinal canal occurs indirectly when the peritoneal sac of the abdomen enters it via the deep inguinal ring.
A direct hernia can occur when the peritoneum enters the canal through its posterior wall, between one of the underlying anatomical structures, that usually have no space between them. A direct hernia is always acquired whereas an indirect hernia can be congenital or acquired. Surgery can correct both direct and indirect hernias.