Inguinal canal

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Inguinal canal

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.

Site

The inguinal canal is situated just above the medial half of the inguinal ligament.

Length

Approximately 4cm (1.57 inches).

Direction

It is oblique directed inferiorly, anteriorly and medially.

Boundaries

A first-order approximation is to visualize the canal as a cylinder, stretching from the deep inguinal ring to the superficial inguinal ring.

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): internal oblique transversus abdominis
anterior wall: aponeurosis of external oblique aponeurosis of internal oblique (lateral third of canal only) superficial inguinal ring (medial third of canal only)	(inguinal canal)	posterior wall: transversalis fascia conjoint tendon (medial third of canal only) deep inguinal ring (lateral third of canal only)
	inferior wall (floor): inguinal ligament lacunar ligament (medial third of canal only) iliopubic tract (lateral third of canal only)

One way to remember these structures is with the mnemonic "MALT", starting at the top and going counterclockwise:

M - muscles
A - aponeuroses
L - ligaments
T - transversalis/tendon

in males : the spermatic cord and its coverings + the ilioinguinal nerve.
in females : the round ligament of the uterus + the ilioinguinal nerve.

The classic description of the contents of inguinal canal in the male are: 3 arteries: artery to vas, testicular artery, cremasteric artery 3 fascial layers: external spermatic,internal spermatic,cremastic 3 other vessels: pampiniform plexus, vas deferens, lymphatics 1 nerve: genital branch of the genitofemoral nerve (L1/2)

The ilioinguinal nerve passes through the superficial ring to descend into the scrotum, but does not formally run through the canal.

Development

During development gonads (ovaries or testes) descend from their starting point on the posterior abdominal wall (para-aortically) and near the kidneys down the abdomen and through the inguinal canal to reach the scrotum. The testis then decends 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.

Disorders

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 inguinal hernia. 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.