The inguinal canal in the groin of men is the remnant of a tube through which the testicle passed before birth from inside the abdomen down into the scrotum. The canal contains the arteries, veins and nerves supplying the testicle, and the vas deferens (sperm tube) that carries sperm from the testicle to the seminal vesicle and penis. The canal is normally just wide enough to contain these structures, but if it opens up, an inguinal hernia occurs as the intestine pushes down into the canal. The canal has an internal inguinal ring made of ligaments at its inner end, and a similar external inguinal ring at its outer end.
For the above reasons, inguinal hernias occur only in men.
The inguinal canal remains a source of weakness in the strong muscle wall of the abdomen, and it may tear open again, allowing some of the gut to protrude into it under the skin of the groin as a hernia.
These hernias may be caused by excess pressure on the lower part of the belly by heavy lifting, prolonged coughing or some other form of strain.
Men who are overweight and have their muscles weakened by fat deposits are more likely to develop them, and the slackening of muscle tone with advancing age can also lead to a rupture.
There is also a hereditary tendency, so that if your father had a hernia, your chances of developing one are increased. In some little boys, the tube does not close properly, and this allows a small amount of fat or intestine to move down the tube from the inside of the abdomen, to form a hernia just under the skin beside the penis.