Table 1.

Comparison of the anatomy of the intestinal tract in humans and animal models

	Human	Mouse	Rat	Pig
Stomach	Four regions: cardia, fundus, body, and pylorus	Three regions: forestomach, body, and pylorus	Three regions: forestomach, body, and pylorus	Four regions: esophagus, cardia, fundus, and pylorus
	pH 1.5 to 3.5	pH 3.0 to 4.0	pH 3.0 to 4.0	pH 1.5 to 2.5
Small intestine	5.5–6.4 m in length	350 mm in length	1,485 mm in length	1.2–2.1 m in length
	pH 6.4 to 7.3	pH 4.7 to 5.2	pH 5.0 to 6.1	pH 6.1 to 6.7
Cecum	Smaller than the colon	Larger than the colon	Larger than the colon	Smaller than the colon
	No fermentation	Main fermentation	Main fermentation	Some fermentation
	pH 5.7	pH 4.4 to 4.6	pH 5.9 to 6.6	pH 6.0 to 6.4
Appendix	Present	Absent	Absent	Absent
Colon	Divided into the ascending, transcending, and descending colon	Not divided	Not divided	Divided into the ascending, transcending, and descending colon
	Main fermentation	No fermentation	No fermentation	Main fermentation
	Thick mucosa	Thinner mucosa	Thinner mucosa	Thick mucosa
	pH 6.7	pH 4.4 to 5.0	pH 5.5 to 6.2	pH 6.1 to 6.6

Adapted from (59, 96, 128, 130, 137, 196)