Normal anatomy

This section gives you a first glance on in vivo architecture of the mucosal layer in the upper and lower GI tract by correlating endomicroscopic images with conventional histology.

		Esophagus

The luminal surface of the esophagus is composed of nonkerati-nized squamous epithelium with polygonal epithelial cells and microvasculature loops within the papillae, which can be recognized during confocal microscopy. Even the intercellular spaces in between single cells can be evaluated. The squamocolumnar junction at the Z-line in the distal esophagus appears individually as a mosaic pattern, with columnar epithelial cells indicating cardiac mucosa.

		Stomach

In the stomach, the architecture of the gastric pits can be observed as small invaginations on the luminal surface, consistent with the known histology of the stomach. The surface cells present a typical cobblestone appearance in endomicroscopy, a finding familiar from electron microscopy.

		Small bowel

Imaging of the duodenum or the terminal ileum allows visualization of intestinal villi, including the brush border. The villi appear as small finger-like extensions projecting from the surface. The epithelial cells covering the villi can be readily identified, and single goblet cells can be identified.

		Colon

In the colon, mucin-containing goblet cells and columnar epithelial cells can be readily identified. The luminal openings of the crypts appear in the horizontal axis as black holes projecting onto the surface of the mucosa, and each crypt is covered with a layer of epithelial cells. The microvascularization is highlighted within the lamina propria in deeper parts of the mucosal layer. The vasculature within the mucosa of the colon shows a typical honeycomb appearance that represents a network of capillaries. Red blood cells are not labeled by fluorescein, and appear as moving black dots in the lumen of the vessels.