The gastrointestinal system of domestic species exemplifies the level of anatomic diversity the domestic species commonly 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 chapter will cover the gastrointestinal system.
Chapter Learning Objectives
By the end of this chapter, you should be able to do the following:
- Describe the histologic layers and subdivisions of the tongue and oral cavity.
- List the histologic and functional differences between glandular and non-glandular gastric mucosa.
- Describe the histologic and functional characteristics of the following gastrointestinal cell types:
- Goblet cells
- Parietal cells
- Chief cells
- Paneth cells
- Describe the interspecies variations of the stomach (gastric) compartment(s), and how this correlates with function.
- Describe and identify the following structures of the tubular digestive tract:
- Muscularis mucosa
- Muscularis externa (tunica muscularis)
- Submucosal plexus and myenteric plexus
- Identify and describe small intestinal microvilli and villi, and understand the functional significance of these epithelial modifications.
- Describe the histologic location and functional role(s) of the Crypts of Lieberkuhn (intestinal crypts).
- Describe the histologic features that distinguish duodenum, jejunum, and ileum (i.e., how can you determine which segment you are examining based on histology?)
- Describe the location(s) and function of the gastrointestinal-associated lymphoid tissue (GALT).
By the end of this chapter, you should be able to answer the following:
- What are the functional roles of gastric Chief cells and Parietal cells, and how do they contribute to the process of digestion?
- What structures and cells normally reside within the lamina propria of the small and large intestine?
- Consider the normal function of intestinal villi and microvilli. Infection with enteric pathogens, such as transmissible gastroenteritis virus of pigs (porcine coronavirus) results in damage to the intestinal enterocytes and villous collapse (atrophy) and fusion. What are the expected clinical consequences of this damage to enterocytes and villi and why (pathogenesis)?
- Parvoviruses, such as canine parvovirus-1 and feline panleukopenia virus, specifically infect cells of the Crypts of Lieberkuhn within the GI tract, resulting in death of cells within the intestinal crypts. What are the clinical consequences of these infections? What are the histologic changes expected following infection of a puppy with canine parvovirus-1 (i.e. if CPV-1 kills cells of the crypts, what consequences does this have to the intestinal mucosa?)