File:IPLab3AcuteAppendicitis2IPLab3AcuteAppendicitis2b.jpg|This is a low-power photomicrograph of a normal appendix on the right and an appendix with acute inflammatory response on the left. Note the abundant blue-stained lymphoid tissue beneath the mucosal layer and the absence of blue-staining cells in the submucosal layer of the normal appendix. Compare this with the extensive distribution of cells throughout the wall of the appendix with acute appendicitis. The blue color is due to the presence of many inflammatory cells, although at this low power these individual cells cannot be specifically identified.File:IPLab3AcuteAppendicitis3IPLab3AcuteAppendicitis3b.jpg|This is a photomicrograph of an appendix exhibiting acute inflammation. Note that there are only remnants of mucosal tissue identifiable along the luminal border of this specimen. There is an extensive infiltration of leukocytes in this tissue which cannot be specifically identified at this low power. Note that the surface is very roughened and has deposits of fibrin.File:IPLab3AcuteAppendicitis4.jpg|This is a photomicrograph of showing the serosal surface of the appendix on with the layer of fibrinopurulent exudate noted in the left gross photo (1). The muscularis (M) and the submucosal tissue in the center submucosa (2S) with remnants of also have a lymphoid nodule. Surrounding this lymphoid nodule are masses of leukocytes which should not be present in a normal appendixrobust inflammatory cell infiltrate.File:IPLab3AcuteAppendicitis5IPLab3AcuteAppendicitis4b.jpg|This photomicrograph of the lumen shows the mucosal surface shows with a small area with of normal mucosal epithelium (arrow). This area is surrounded by areas of ulceration the ulcerated mucosa with an inflammatory infiltrate of infiltrates comprising primarily neutrophils with a few lymphocytes and neutrophilsmacrophages.File:IPLab3AcuteAppendicitis6IPLab3AcuteAppendicitis5b.jpg|This TThis higher-power photomicrograph of the mucosal surface shows the loss of normal mucosal epithelium (arrows) and the inflammatory infiltrate. The principal inflammatory cell in this case of acute appendicitis is the neutrophil.