Connective tissue proper is composed of cells, fibers and ground substance. Fibrocytes are the basic cell of connective tissue with other cell types including mast cells , plasma cells , macrophages , and pigmented cells scattered throughout the tissue. Collagen , elastic and reticular fibers form the structural matrix which is surrounded by the cells and amorphous ground substance of connective tissue. The central connective tissue core of the villous contains plasma cells which can be seen at higher magnification. Note the prominent granules in the cytoplasm of these cells.
Mast cells stain strongly metachromatic with toluidine blue as shown below.
These cells contain the golden pigment, hemosiderin. Pigmented cells are widely distributed throughout the body in connective tissue and other tissues. Slide 24, Lymph node , dog, Gridley's Pancreas is also present on this slide. The fibers stain black with the Gridley's stain. The image on the left is a high magnification of the wall of the aorta.