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Content provided by Jon Lund
Clinical Associate Professor, School of Graduate Entry Medicine & Health, University of Nottingham

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Introduction	Learning Objectives	Definition	Anatomy	Symptoms, Signs and Complications	Examination	Operation	Quiz

Anatomy of the Inguinal Canal

The inguinal canal is about 4cm long and lies above the medial half of the inguinal ligament (the inguinal ligament is the rolled under edge of the external oblique and is attached at the lateral end to the anterior superior iliac spine and at its medial end to the pubic tubercle). The lateral end of the inguinal canal is the deep inguinal ring, which is an opening in the transversalis fascia. The deep ring lies just above the half way point of the inguinal ligament and through it passes spermatic cord in the male, the round ligament of the uterus in the female and the ilioinguinal nerve in both sexes. The roof, floor, anterior and posterior walls of the inguinal canal are made from adjacent muscles and fascia. At the medial end of the canal is its opening at the superficial inguinal ring, which is a gap in the aponeurosis (flattened tendon) of the external oblique muscle. The contents of the canal pass out of the canal at the superficial ring. The spermatic cord enters the scrotum in the male and the round ligament of the uterus passes into the labia in the female.

diagram of the inguinal canal

Anatomy in more detail

	The right inguinal region with skin and subcutaneous tissue removed. Note the inguinal ligament - it can be seen that this is merely the rolled under lower edge of the external oblique. The external inguinal ring can be seen as an opening in the external oblique aponeurosis.

The right inguinal region in a male. The external oblique has been removed to reveal the contents of the canal. Note the spermatic cord covered with muscle. This muscle is called the cremaster and originates from all three layers of muscle of the abdominal wall. Note also the femoral vessels emerging from below the inguinal ligament as they pass into the leg.

	The right inguinal region in a male. The cremaster has been stripped from the cord and it has been retracted to show the floor of the canal. Note the inferior epigastric vessels just medial to the deep inguinal ring. Any hernia which develops medial to these vessels is a direct hernia. Any hernia which develops lateral to these vessels is an indirect hernia.

Boundaries of the inguinal canal

	Lateral Third	Middle Third	Medial Third
Posterior wall	Transversalis fascia and deep inguinal ring	Transversalis fascia	Transversalis fascia and conjoint tendon
Anterior wall	Aponeurosis of external oblique and internal oblique	Aponeurosis of external oblique	Aponeurosis of external oblique and superficial inguinal ring
Roof	Arching over fibres of internal oblique and transversus abdominis	Arching over fibres of internal oblique and transversus abdominis
Floor	Inguinal ligament	Inguinal ligament	Inguinal ligament

Contents of the spermatic cord

Arteries	Testicular artery Artery to the Vas deferens Cremasteric artery
Veins	Pampiniform plexus (a plexus of veins draining the testis)
Lymphatics	From the testis, draining to the para aortic nodes (NB lymph from the testis does not drain to the inguinal nodes)
Nerves	Genital branch of the genitofemoral nerve (to cremaster muscle) Sympathetic nerves with the arteries
Other	Vas deferens

See anatomical knowledge applied in a video showing repair of an inguinal hernia with mesh.