Stomach
The stomach is the site where food is mixed with gastric juice and reduced to a fluid mass called chyme. This slide shows the structure of the stomach lining under the light microscope. Begin by identifying the folds of the stomach wall, or rugae, which are visible in a gross specimen. The layers of the stomach wall follow the basic plan described above. The gastric glands are the basic structure of the stomach wall and can be thought of as tiny pits, or indentations, lined by epithelial cells. The loose connective tissue of the submucosa contains some blood vessels that can be discerned upon close observation. The muscularis externa of the stomach is notable because it contains an additional muscular layer. It is structured with inner oblique, middle circular, and outer longitudinal layers. This structure allows for the churning movements that mix the chyme and expose it to the acidic gastric juice produced by the stomach glands.
Esophagus
The esophagus is a muscular tube that transports food from the pharynx to the stomach. It is lined by a stratified squamous epithelium and has a prominent muscularis mucosa and thick muscularis externa. The muscularis externa of the esophagus is unique in that it transitions from striated to smooth muscle over the length of the tube. The esophagus ends in the gastro-esophageal junction.
Large Intestine
The large intestine absorbs water and concentrates waste material that is formed into feces. It lacks villi and contains a disproportionately large number of goblet cells. The lamina propria has many macrophages, plasma cells, eosinophils, and lymphoid nodules.
Stomach
The stomach is the site where food is mixed with gastric juice and reduced to a fluid mass called chyme. This slide shows the structure of the stomach lining under the light microscope. Begin by identifying the folds of the stomach wall, or rugae, which are visible in a gross specimen. The layers of the stomach wall follow the basic plan described above. The gastric glands are the basic structure of the stomach wall and can be thought of as tiny pits, or indentations, lined by epithelial cells. The loose connective tissue of the submucosa contains some blood vessels that can be discerned upon close observation. The muscularis externa of the stomach is notable because it contains an additional muscular layer. It is structured with inner oblique, middle circular, and outer longitudinal layers. This structure allows for the churning movements that mix the chyme and expose it to the acidic gastric juice produced by the stomach glands.
Esophagus
The esophagus is a muscular tube that transports food from the pharynx to the stomach. It is lined by a stratified squamous epithelium and has a prominent muscularis mucosa and thick muscularis externa. The muscularis externa of the esophagus is unique in that it transitions from striated to smooth muscle over the length of the tube. The esophagus ends in the gastro-esophageal junction.
Large Intestine
The large intestine absorbs water and concentrates waste material that is formed into feces. It lacks villi and contains a disproportionately large number of goblet cells. The lamina propria has many macrophages, plasma cells, eosinophils, and lymphoid nodules.