It is difficult to appreciate on slides, as it is often removed in the processing of the tissue. Collagenous and reticular fibres are made from a family of protein types called collagen. The different types of collagen are labelled with Roman numerals. Currently, there are 14 different types, with types I, II , III and IV being the most common. The different fibre arrangements give rise to many different connective tissue structures, from the thin, sheet-like basal lamina which many cells rest on, to the large, strong fibre bundles which make up tendons.
Elastic fibres serve a slightly different purpose in that they give resiliency to a tissue.
They are composed of proteins know as elastins, whose special bonding to one another allows for stretching without breaking. On this page, we will focus on the embryonic connective tissue and on the ordinary connective tissue types. Here we see typical mesenchymal cells. These fibres require a special stain to visualize well. This image is at a lower magnification than the one on the left.