Front of abdomen, showing surface markings for arteries and inguinal canal. (Inguinal canal is tube at lower left.)
The inguinal canal is a passage in the anterior (toward the front of the body) abdominal wall which in men conveys the spermatic cord and in women the round ligament. The inguinal canal is larger and more prominent in men. There are two canals, on the left and right sides of the abdomen.
The inguinal canal is situated just above the medial half of the inguinal ligament. In both sexes the canal transmits the ilioinguinal nerve. The canal is approximately 3.75 to 4 cm long., angled anteroinferiorly and medially.
A first-order approximation is to visualize the canal as a cylinder, 
To help define the boundaries, the canal is often further approximated as a box with six sides. Not including the two rings, the remaining four sides are usually called the "anterior wall", "posterior wall", "roof", and "floor". These consist of the following:
|superior wall (roof):
Medial crus of aponeurosis of external oblique
Musculoaponeurotic arches of internal oblique and transverse abdominal
aponeurosis of external oblique
fleshy part of internal oblique (lateral third of canal only)
superficial inguinal ring (medial third of canal only)
|(inguinal canal)||posterior wall:
conjoint tendon (Inguinal falx,reflected part of inguinal ligament, medial third of canal only)
deep inguinal ring (lateral third of canal only)
|inferior wall (floor):
lacunar ligament (medial third of canal only)
iliopubic tract (lateral third of canal only)
During development gonads (ovaries or testes) descend from their starting point on the posterior abdominal wall (para-aortically) from labioscrotal swelling near the kidneys down the abdomen and through the inguinal canal to reach the scrotum. The testis then descends through the abdominal wall into the scrotum, behind the processus vaginalis (which later obliterates). Thus lymphatic spread from a testicular tumour is to the para-aortic nodes first, and not the inguinal nodes.
The structures which pass through the canal differ between males and females:
The classic description of the contents of spermatic cord in the male are:
Abdominal contents (potentially including intestine) can be abnormally displaced from the abdominal cavity. Where these contents exit through the inguinal canal the condition is known as an indirect or oblique inguinal hernia. This can also cause infertility. This condition is far more common in men than in women, owing to the inguinal canal's small size in women.
A hernia that exits the abdominal cavity directly through the deep layers of the abdominal wall, thereby bypassing the inguinal canal, is known as a direct inguinal hernia.
|Wikimedia Commons has media related to Inguinal canal.|
^ Adam Mitchell; Drake, Richard; Gray, Henry David; Wayne Vogl (2010). Gray's anatomy for students. Elsevier/Churchill Livingstone. pp. 286. ISBN 0-443-06612-4.