Inguinal canal is an oblique slit-like passage through the lower part of the anterior abdominal wall that extends in the downward and medial direction. The inguinal canal begins at the deep inguinal ring and continues for approximately 4 cm, ending at the superficial inguinal ring.
In the males, it allows a genital branch of the genitofemoral nerve and spermatic cord to pass to and from the testis to the abdomen. In females, it allows the round ligament of the uterus to pass from the uterus to the labium majus. The ilioinguinal nerve passes through part of the canal exit through the super inguinal ring with other contents. The inguinal canal has a deep inguinal ring and superficial inguinal ring.
Deep inguinal ring
The superficial (internal) inguinal ring is the beginning of the inguinal canal. It has an oval shaped opening in midway between the anterior superior iliac spine and the symphysis pubis above the inguinal ligament. Sometimes referred to as a defect or opening in the transversalis fascia. In male, the margins of the ring give attachment to the internal spermatic fascia. Round ligament of the uterus in the female.
Superficial inguinal ring
The superficial (external) inguinal ring is the end of the inguinal canal. It is a triangular-shaped defect in the aponeurosis of the external oblique muscle and lies immediately above and medial to the pubic tubercle. The margins of the ring, sometimes give attachment to the external spermatic fascia sometimes called crura.
Inguinal canal boundaries
Anterior wall of Inguinal Canal:
The anterior wall is formed by the entire length of the external oblique muscle. The external oblique muscle aponeurosis is reinforced laterally by the lower fibers of the internal oblique which further strengthens the anterior wall.
Posterior wall of Inguinal Canal :
The posterior wall of the inguinal canal is formed by the transversalis fascia and conjoint tendon. It is reinforced along its medial one-third by the conjoint tendon. The conjoint tendon is the combined insertion of the transversus abdominis and internal oblique muscles into the pubic crest and pectineal line.
Roof (superior wall) of inguinal Canal :
The roof of the inguinal canal is formed by the arching fibers of the transversus abdominis and internal oblique muscles.
Floor (inferior wall) of inguinal Canal :
The floor of the inguinal canal is formed by the medial one-half of the inguinal ligament also known as poupart ligament. So floor (inferior wall) is formed by upturned lower edge of the inguinal ligament and its medial end is formed by the lacunar ligament.
Contents of the Inguinal canal :
The content of inguinal canal are
- The spermatic cord in men
- The round ligament of the uterus and genital branch of the genitofemoral nerve in women.
The spermatic cord is a collection of structures that pass through the inguinal canal to and from the testis.
It begins at the deep inguinal ring lateral to the inferior epigastric artery and ends at the testis.
Structures of the spermatic cord
- Vas deferens: (The vas deferens is a cordlike structure that transport spermatozoa)
- Testicular artery: (A branch of the abdominal aorta. It traverses the inguinal canal and supplies the testis and the epididymis)
- Testicular veins: (Extensive venous plexus, the pampiniform plexus, leaves the posterior border of the testis. it drains into the left renal vein on the left side and into the inferior vena cava on the right side)
- Testicular lymph vessels: (The testicular lymph vessels ascend through the inguinal canal to reach the lumbar (para-aortic) lymph nodes on the side of the aorta at the level of the 1st lumbar vertebra.
- Autonomic Nerves (Sympathetic fibers run with the testicular artery from the renal or aortic sympathetic plexuses. Afferent sensory nerves accompany the efferent sympathetic fibers.
- Processus Vaginalis: (Remains of the processes vaginalis)
- Genital Branch of the Genitofemoral Nerve: (Supplies the cremaster muscle)
Round ligament of the uterus :
The round ligament of the uterus is a cord-like structure that passes from the uterus to the deep inguinal ring where it enters the inguinal canal. The round ligament of the uterus is the long distal part of the original gubernaculum in the fetus that extends from the ovary to the labioscrotal swellings.
Development of the Inguinal Canal
During developments of testis and gonads in abdominal cavity, each testicle descends from starting point of posterior abdominal wall down abdomen and through inguinal canal to the scrotum. Testicle descends behind gubernaculum which later obliterates. During descends it carries covering from each layer result in formation of inguinal canal.
A peritoneal diverticulum called the processes vaginalis is formed before the descent of the testis and the ovary from their site of origin high on the posterior abdominal wall (L1).
Internal spermatic fascia:
(Derived from the fascia transversalis)
The processus vaginalis passes through the layers of the anterior abdominal wall. It acquires a tubular covering from each layer when it traverses the fascia transversalis at the deep inguinal ring and acquires a tubular covering this is called internal spermatic fascia.
Cremasteric fascia :
(Derived from the internal oblique muscle)
As processus vaginalis passes through the lower part of the internal oblique muscle, it takes with it some of its lowest fibers, which form the cremaster muscle. The muscle fibers are embedded in fascia, and thus the second tubular sheath is known as the cremasteric fascia. Transversus abdominis muscle has not acquired a covering.
External spermatic fascia:
(Derived from the external oblique aponeurosis)
The processus vaginalis on reaching the aponeurosis of the external oblique. It evaginates external oblique aponeurosis to form the superficial inguinal ring. Here it acquires a third tubular fascial coat, the external spermatic fascia. In the female, the term spermatic fascia should be replaced by the covering of the round ligament of the uterus.
It is a band of mesenchyme, extending from the lower pole of the developing gonad through the inguinal canal.
In the male the testis descends through pelvis and inguinal canal during the seventh and eighth months of fetal life. The testis follows the gubernaculum and descends.
In the female, the ovary descends into the pelvis following the gubernaculum. The gubernaculum becomes attached to the side of the uterus. That part of the gubernaculum extending from the uterus into the developing labium majus persists as the round ligament of the uterus.
Inguinal canal clinical significance:
Abdominal wall is a complex design, but the only natural weakness caused by inadequate muscular strength is posterior wall of inguinal canal and lumber triangle. This results in hernia.
Hernia: A hernia is the bulging of part of the contents of the abdominal wall through a weakness in the abdominal wall.
An inguinal hernia is the protrusion or passage of a peritoneal sac, with or without abdominal contents, through a weakened part of the abdominal wall in the groin region. There are two types direct inguinal hernia and indirect inguinal hernia.
Indirect inguinal hernia: (through the deep inguinal ring)
The indirect inguinal hernia is the most common of the two types of an inguinal hernia and is much more common in men than in women. The protruding peritoneal sac enters the inguinal canal by passing through the deep inguinal ring, just lateral to the inferior epigastric vessels.
Direct inguinal hernia: (through the posterior wall of the inguinal canal)
The direct inguinal hernia is peritoneal sac that enters the medial end of the inguinal canal directly through a weakened posterior wall. a hernia is medial to the inferior epigastric vessels.
Inguinal Triangle ( Hesselbach ’ s triangle ),
Inguinal triangle is present in groin region which is bounded:
Laterally: Inferior epigastric artery
Medially: Rectus abdominis muscle
Inferiorly: Inguinal ligament.
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