The stomach and other parts of the gastrointestinal system are layered structures. In the stomach, the innermost stratum (nearest the lumen) is the mucosa, which is comprised of an epithelial lining, a loose layer of connective tissue called the lamina propria, and the muscularis mucosa, which consists of smooth muscle tissue. The next division of the stomach is the submucosa, a stratum of connective tissue interspersed with many blood and lymphatic vessels. Surrounding the submucosa is the muscularis externa, which is composed of three layers of muscle rather than only two layers, as it is in other sections off the gastrointestinal tract. The outermost stratum of the stomach is a covering of connective tissue called the serosa or adventitia.

The sample of rat stomach tissue featured in the digital image above was labeled with Texas Red conjugated to wheat germ agglutinin, a lectin that selectively binds to sialic acid residues found in both mucoproteins and glycoproteins. The cells were also stained with Alexa Fluor 488 conjugated to phalloidin and the dye Hoechst 33342, which target the cytoskeletal filamentous actin network and nuclear DNA, respectively. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.