Figure 3.

Differences in anatomy and microbiota (on genus level) of the small intestine (SI) between two animal models (mouse and pig) vs. humans

Upper part: the length of the SI in comparison with the other gut compartments is shown. Mice have a forestomach and a glandular stomach, while pigs and humans have a glandular stomach, but the pig’s stomach is two to three times larger than the human stomach. Middle part: the anatomical structure of the luminal small-intestinal wall is shown, highlighting the absence of plicae circulares or mucosal folds in mice in contrast to pigs and humans. In mice, the finger-shaped villi are directly oriented on the small-intestinal muscle layer (muscularis mucosa), making the mucosal surface smooth. In pigs and humans, there are plicae circulares in distal duodenum, jejunum, and proximal ileum. Lower part: dominant bacterial genera in the SI.