The source for this specimen should be obvious (and confidently
so), provided you are familiar with the organ it represents.
You should easily see three distinct layers, 1 mucosa, 2
submucosa, and 3 muscularis. Only one organ system has
such distinct layers.
The mucosa is unique. Note that the mucosa is packed with glandular
tissue, which extends from the surface all the way to the muscularis
mucosae. Also note that there is relatively little lamina propria,
visible only as inconspicuous strands separating the glands.
Note that the mucosal glands contain more than one cell type, and that
cells of the surface epithelial cells differ markedly from those of
the glands.
Only one organ has features like this.
No more hints.
