The esophagus is a tubular component of the vertebrate digestive system. In mammalian species, the esophagus extends from the pharynx to the stomach. The role of this part of the alimentary canal is to serve as a conduit for food taken into the body. Wavelike contractions (known as peristalsis) of the esophageal wall force the food along length of the muscular tube. Mucus glands located in the wall help lubricate the food and ease its movement along the provided path.

As the first major section of the gastrointestinal tract, the esophagus encounters food that has only undergone minimal previous digestive processing via mastication and exposure to saliva. It must, therefore, be able to withstand exposure to rough or coarse material like potato chips, broccoli, or even small bits of bone without significant damage. The interior of the upper part of the esophagus is lined with stratified squamous epithelial cells, which heal quickly and are resistant to abrasion and heat. The lower portion of the tube, however, is lined with columnar cells.

The rat esophagus tissue section illustrated in the digital image above was stained with Texas Red conjugated to wheat germ agglutinin, a plant-derived lectin that targets the Golgi apparatus, as well as Alexa Fluor 488 conjugated to phalloidin for cytoskeletal actin. Nuclei were labeled with Hoechst 33342. 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.

Rat Esophagus Tissue Section Labeled with Wheat Germ Agglutinin and Phalloidin Conjugates - Located at each end of the esophagus is a ringlike band of muscle fibers, termed a sphincter. Usually the upper and lower esophageal sphincters are constricted, preventing continual entry of air into the esophagus or the leakage of stomach contents into the tract. The sphincters relax during swallowing, however, to facilitate the passage of food.

Lectin Carbohydrates and Filamentous Actin Visualized in a Rat Colon Sample - Most people experience heartburn occasionally during their lifetimes, usually with no long-term ill effects. Heartburn that occurs regularly over a long period of time or that is unusually severe, which is characteristic of gastroesophageal reflux disease (GERD), can be very detrimental, however. Without treatment, the esophagus may be chronically irritated in such patients and may lead to a condition known as Barrett’s esophagus.