Intestine Flashcards
List 6 types of epithelial cells in the Intestine
- Enterocytes
- Crypt epithelial cells
- Goblet cells
- Paneth’s cells
- Enterochromaffin cells
- M cells
List 4 types of mesenchymal cells in the Intestine
- Thelio-lymphocytes
- Neutrophils
- Eosinophils
- Globule luekocytes
Three functions of the intestine:
- Absorption
- Digestion
- Secretion
The villi of the small intestine greatly increase the absorptive area. They are lined by __________ cells, and have an enzymatically rich brush border consisting of the _________ (a filamentous layer) and ______.
- columnar epithelial cells
- glycocalyx
- Microvilli
The large intestine’s main functions are (2)
- Resorption of fluids
- Lubcrication via goblet cells
Crypt epithelial cells migrate up the villi, undergo matration, and eventually shed at the tips into the lumen. This takes about how many days? Is the turnover rate faster or slower in the large bowel?
- 2-4 days
- Slower in the large bowel
Pathogenesis of Diarrhea
Malabsorption - explain process
- Nutrients are not absorbed in small intestine
- Sugars and other nutrients pass to large intestine
- Sugars are split by bacteria in large intestine into osmotically active particles
- Water and other solutes are held in large intestine
- Excreted as diarrhea
Gross lesions of malabsorption induced by viral enteropathy
- Neonatal animals
- Thin
- Milk curd in stomach
- Thin walled small intestine
- Watery content of colon
- Lacteals empty
Several viruses selectively affect the villus absorptive epithelium:
How does the rotavirus do it?
- Destroys cells on tip of the villus
- Lose mature enzyme producing and absorptive cells
- Villus atrophy develops
Epizootic diarrhea of infant mice, acute gastroenteritis of piglets, neonatal calf diarrhea, and human infantile gastroenteritis are all diseases caused by this type of virus:
rotavirus
Several viruses selectively affect the villus absorptive epithelium:
How does the coronavirus do this?
- Destroys epithelial cells in the middle portion of the villus
- Lose mature enzyme producing and absorptive cells
- Villus atrophy develops
- May infect colonic epithelium
Transmissible gastroenteritis in pigs, porcine epidemic diarrhea, neonatal calf diarrhea, turkey bluecomb disease virus are all diseases caused by this type of virus:
Coronavirus
Several viruses selectively affect the villus absorptive epithelium:
How does parvovirus do this?
- Destroy cypt epithelium
- Produces viremia first
- Infects mitotically-active cells of the intestinal crypt epithelium and lymphoid tissues
- Crypts are destroyed. Villus atrophy developes
- Loss of mucosal epithelium expose lamina propria and allows bile to stain inner surface of itnestine
Feline panleukopenia virus and mink enteritis virus are examples of this type of viral disease.
Parvoviral
Feline panleukopenia virus:
- How do bacteria affect the turnover rate of absorptive epithelial cells? And how does this affect the viral infection?
- What is the difference between conventional and specific pathogen-free cats and germ-free cats?
- Lesions are most severe in conventional and specific pathogen-free cats, and least severe in germ-free cats
- Bacteria and bacterial products increase the turnover rate of the absorptive epithelial cells. This stimulates crypt cell replication which in turn favors viral replication in the intestines of conventional and SPF cats.
- The intestinal epithelial cell turnover rate is 2-4 days in conventional animals, and 7-10 days for germ-free animals
Several viruses selectively affect the villus absorptive epithelium:
How does the BVD virus do this?
What are the lesions?
- Destroys crypt epithelium
- Infects mitotically active cells of the intestine and lymphoid system
- Petechial hemorrhages in spiral colon
BVD virus is what type of virus? Family?
RNA or DNA virus?
- Pestivirus in family Flaviviridae
- RNA virus
How is radiation exposure and radiomimetic drugs identical to parvoviral infection? What is the main difference?
- They destroy the mitotically-active cell population and produce intestinal lesions that are identical to parvoviral infection
- Except that no inclusion bodies are formed
Cryptosporidiosis causes malabsorption of the small intestine.
- Agent?
- Infests _______ of the small itnestine
- Infects ______ hosts
- Produces thick _____ content of small and large itnestines
- Prevents ______ of nutrients
- Cryptosporidium parvum
- brush border
- immunodeficient
- mucoid
- absorption
In hypersecretion, _____ (old/neonatal) animals are affected. Intestinal epithelium secretes _____ and ______ into lumen.
- Neonatal
- Water
- Electrolytes
Enterotoxigenic E. coli cause diarrhea due to what kind of pathogenesis?
Describe how they do this.
- Hypersecretion
- Enterotoxigenic E. coli attach to enterocyte via pilus
- Produce toxin that activates adenyl cyclase
- This causes intestinal epithelium to secrete water and electrolytes into the lumen
Lesions of Colibacillosis:
- Small intestine?
- Thickness of wall?
- Lacteals?
- Intestinal epithelium?
- Gross - fluid filled small intestine
- Normal thickness of wall
- Lacteals full
- Intestinal eptihelium is undamaged
Exudation
____ - losing enteropathies
protein
Explain pathogenesis of diarrhea caused by exudation
- Protein-losing enteropathies - proteins are lost into the gut lumen
- Increased shedding of mucosal epithelial cells
- effusion of plasma proteins
- Altered permeability of lymphatics, blood vessels or tight junctions between epithelial cells - non selective loss of plasma proteins
Intestinal lymphangiectasia, Chronic Inflammatory Bowel Disease, and Intestinal lymphosarcoma are all causes of enteric _____-____
Enteric protein-loss (diarrhea due to exudation)
The most commonly reported cuase of protein-losing enteropathy is?
Canine Intestinal Lymphangiectasia
Canine Intestinal Lymphangiectasia
- Symptoms
- How do dogs get it?
- Cause?
- Lesions?
- Diarrhea, steatorrhea, hypoproteinemia, ascites
- Congenital or acquired secondarily to lymphatic obstruction
- Usually idiopathic
- Thickened intestinal mucosa, dilated lymphatics and lacteals
Hypermotility
- Increased rate, intensity, or frequency of peristalsis
- Not usually a primary mechanism
- Causes decreased mucosal contact time
- May not have a morphologic change
Clostridium perfringens type C. and Clostridium difficile cause severe ______ enteritis via _______ cytotoxicity.
- Severe necrohemorrhagic enteritis
- Direct toxin-mediated cytoxocity
Clostridial Enterotoxemia
- Agent
- Occurs in pigs under ____ days of age
- what toxin causes necrosis of epithelium?
- mortality?
- What happens to stomach and intestine?
- Clostridium perfringens type C
- 7
- Exotoxin
- High death loss in pigs of susceptible litters
- Distension of stomach with milk causes hypomotility of gut and development of anaerobic environment in intestine.
- Segmental hemorrhage in jejunum
- Mucosa of segments on small intestine may be covered by tenacious tan friable exudate
- Necrosis of epithelial lining with fibrinous exudate and intense infiltration by neutrophils.
Clostridium perfringes type D
- What animals does it affect?
- How do they acquire it?
- Symptoms?
- This agent causes endothelial cell damage. What results from this?
- Sheep, goats, calves
- Sudden change in diet to easily digested carbohydrates
- Sudden death
- Overgrowth of organism in small intestine
- Endothelial cell damage (fibrinoid necorsis):
- Multisystemic hemorrhages
- Pericardial effusion
- Mild gastroenteritis
- Bilateral symetrical encephalmalacia
Clostridium perfringes type D infection in sheep is also called _____
Puply Kidney Disease
Canine Hemorrhagic Gastroenteritis
- Agent suspected?
- What kinds of dogs are affected (breeds/age)
- Symptoms
- Can death result?
- Lesions?
- What part of the intestinal epithelium is spared?
- Clostridium perfringes type E
- Toy and miniature breeds 2 years or less
- Depressed, diarrhea, vomiting, blood at anus
- Life threatening
- Hemorrhagic necrosis in mucosa of GI tract and numerous clostridia in intestinal debris
- Crypts are spared
Tyzzer’s Disease:
- Agent
- What animals does it affect?
- Lesions
- Microscopic lesions
- Clostridium piliformis (Bacillus piliformis)
- Rodents - guinea pigs, hamsters, gerbils; and lagomorphs (rabbits)
- Less commonly seen in rats, mice, cats, dogs, and horses
- Enterocolitis and necrotizing hepatitis
- “hay stack” arrangement of filamentous organisms in silver or giemsa stained sections
Tyzzer’s Disease is also called _____ in rodents and lagomorphs.
Wet Tail
Clostridium difficile is an opportunistic infection that is associated with disruption of normal flora and overgrowth.
- Treatment
- Produces what exotoxins? What test can detect these exotoxins?
- What does it cause in horses, foals, baby pigs, lab animals, primates (and humans), and dogs?
- Antibiotics
- Produces A and B exotoxins - detected by ELISA
- Necrotizing enterocolitis in horses (colitis X?)
- Hemorrhagic necrotizing colitis in foals
- Mesocolonic edema and typhylocolitis in baby pigs
- Enteritis in lab animals
- Pseudomembranous colitis in primates, including humans
- Shed by dogs
Numerous agents cause damage of structural integrity of intestinal epithelial cells leading to local inflammation and cytotoxic damage.
How does enteroadherent E. coli do this?
What are the lesions?
- Via intimate contact between pathogen and brush border - attaching and effacing
- Enteroadherent E. coli attach to absorptive epithelium of intestine effacing the microvilli
- Also attaches to gallbladder epithelium
- Intestine is dilated and fluid filled
- Causes exfoliation and villus atrophy
Numerous agents cause damage of structural integrity of intestinal epithelial cells leading to local inflammation and cytotoxic damage.
- How do Salmonella sp. do this?
- Symptoms?
- Lesions
- How is it transmitted?
- Invasion of intestinal epithelium - M cells serve as a portal of entry
- Hosts may be inapparent carriers or may have septicemia, acute enteric disease, or chornic enteritic disease
- Salmonellosis may cause enterocolitis = thickening of wall of intestine, and mesenteric lymph nodes may be enlarged, mucosal surface may be covered by tenacious friable diphtheritic membrane
- Paratyphoid nodules in liver and button ulcers in colon may be seen
- Ingested in contaminated feedstuff, from fomites, or contact with infected animals