There are some terms in pathology that are used interchangeably – but shouldn’t be. “Reticulin” and “collagen” are two of these terms. Reticulin fibers are the same thing as type III collagen. They are fine, delicate fibers made by fibroblasts. There are other types of collagen (types I, II, and IV are the main ones, but there are more) that have different appearances and are found in different places. Type I collagen is the main component of bone, type II is the main component of cartilage, and type IV is the main component of basement membranes.