Your abdominal area has many muscles encasing and protecting your vital organs. Sometimes, though, a muscle might have a weak area or even a hole through which an organ can protrude. And then you have yourself a hernia.
The abdominal area can have a variety of different types of hernias such as hiatal hernias, umbilical hernias and incisional hernias. One other type of hernia is the midline hernia. This will happen in the midline of the abdomen, hence the name. The midline hernia is the second most common type. Midline hernias are repaired with mesh, which does a sturdier and more permanent job of repair than sutures did.
"Other parts of the body can also have organ herniation. For example, people often talk about their back having ‘slipped a disc’, which is actually inaccurate as the situation is caused by interior spine material ‘herniating’ out from between the discs. A hernia is a bulge or protrusion of an organ through a muscle or other structure that normally serves to keep it contained."
http://www.incapitalhealth.co.uk/2010/05/midline-and-inguinal-hernias-%E2%80%93-latest-treatment-options-from-london-teaching-hospital-specialists/