InterFIG 4: Arcade rings (TEM, transverse section).
The level of the section is indicated in the top inset.
Thin rings of anterior (opaque yellow) and posterior (transparent yellow) arcade tissue encircle the anterior two-thirds of the buccal cavity. Similar to hypodermal tissue, the rings have amorphous extensions (arrow) that insert around the neighboring tissues (visible [arrowhead] in the top inset). Posterior to the rings, the arcade tissues become two thin processes that run next to the pharyngeal procorpus (bottom inset). Bar, 1 μm. (Image source: [MRC] N2T A59-16.)
Click on picture for full resolution image.