The gastrointestinal system of domestic species exemplifies the anatomic diversity encountered in veterinary medicine. Despite this diversity, the gastrointestinal system of all species is unified through the primary goal of breaking down ingested nutrients for absorption and utilization. This process begins with prehension and ingestion, and follows with digestion, absorption, and waste elimination. Knowledge of the microscopic anatomy of the gastrointestinal tract goes hand-in-hand with understanding the functionality of this system. Additionally, knowledge of the histology will greatly aid the veterinarian in understanding the processes, infectious and otherwise, that mediate clinical disease in these species.