The inguinal canal is a small passage that leads through the lower abdominal wall. Present in both sexes, the canal permits structures to pass from the abdomen to the genital region. It carries the spermatic cord in males, and the round ligament of the uterus in females. Blood vessels, lymph vessels, and the ilioinguinal nerve also pass through this area. Occasionally, part of the gut may protrude through the passage, forming a hernia.
The anatomy of this canal can be difficult for students to grasp, due to its complex, three-dimensional nature, but with patience it can be understood. The canal itself is tiny, measuring about 1.5 inches (about 4 cm) in length. It runs at an angle down toward the midline, at a level just above the skin crease where the abdomen joins the thigh. Abdominal muscles and tissues make up the sides, roof, and floor. As human beings are generally symmetrical, an individual has two inguinal canals, one on each side.
Forming the entrance to the passageway is an opening called the deep inguinal ring. It consists of a gap in the fascia transversalis — a thin layer of tissue lining the abdominal muscle. An exit from the canal is created by a hole in the external abdominal muscle, just above the pubic bone. This opening is known as the superficial inguinal ring.
In males, the inguinal canal allows the spermatic cord to travel from the abdomen to the testis. The spermatic cord contains the vas deferens — the tubular structure that transports sperm — together with blood vessels and nerves. Sperm is manufactured outside of the abdomen in the testes because the process requires cooler temperatures than those existing inside the abdominal cavity.
The canal in females conveys the round ligament of the uterus with its attendant nerves and blood vessels. Normally, the uterus is bent forward and angled toward the front of the body, and the round ligament helps to keep it in position. Pregnancy may cause stretching of the ligament, but this need not cause problems as long as general muscle tone is sound.
In some people, a portion of viscera, or gut, may protrude through the inguinal canal, causing a swelling in the groin. This is known as an inguinal hernia and is more commonly found in men. The lump may be present from childhood or appear later in life, typically following heavy lifting, straining, or coughing.
Inguinal hernias should be assessed by a medical professional. If left untreated, they may enlarge and this can lead to complications. The piece of gut may become pinched or twisted, cutting off its blood supply; intestinal blockage or gangrene could result. Using open or keyhole surgery, a hernia can be pushed back inside the abdomen and the defect in the abdominal wall repaired using synthetic mesh.