Fig. 1.
Brightfield photomicrographs showing the histology of the mouse colorectum in longitudinal (A–D) or transversal (E–F) sections. G: measurements of colorectal muscle and mucosal layer thicknesses. Inspection of the longitudinal section of distal colon and rectum in A clearly shows the progressive decrease in thickness of the tissue layers. Boxes 1, 2, and 3 are shown at high-power magnification in B, C, and D, respectively, to depict the differences between proximal, middle, and distal areas of the colorectum (*longitudinal muscle layer; **circular muscle layer; arrows, myenteric plexus; M, mucosa). A similar difference in muscle layer thickness is shown in transversally cut sections of the colon (E) and rectum (F). Scale bar = 1,000 μm for A and 100 μm for B–F (scale bar in D also applies to B and C).