Diverticulum

In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false.
In medicine, the term usually implies the structure is not normally present, but in embryology, the term is used for some normal structures arising from others, as for instance the thyroid diverticulum, which arises from the tongue.
The word comes from Latin "dīverticulum", "bypath" or "byway".
Classification.
Diverticula are described as being true or false depending upon the layers involved:
Human pathology.
Gastrointestinal tract diverticula.
Most of these pathological types of diverticula are capable of harboring an enterolith. If the enterolith stays in place, it may cause no problems, but a large enterolith expelled from a diverticulum into the lumen can cause obstruction.