Once again, notice how dense the collagen fibers are and the low cellularity, when compared to the loose connective tissue we have observed previously. Fibroblasts/fibrocytes are not too difficult to identify because of their rod-shaped nuclei. The fibroblast nuclei will be larger and less heterochromatic because they are more active. Macrophages are a bit harder to positively identify, unless we can see something they have phagocytized. Most likely, they make up the majority of the other cells seen here. Fibroblasts, fibrocytes and macrophages are the most common cell types found in dense, irregular connective tissue. The spaces inbetween the collagen fibers contain amorphous ground substance.