Chapter 13: GI Small Intestine Structural and Infections Flashcards
What are the plicae circularis and peyer patches?
Plicae circularis: Spiral folds of mucosa and submucosa.
Peyer patches: Lymphoid aggregates in submucosa.
Describe vascular and neurologic innervation of the small intestine.
Duodenum: Pancreaticoduodenal branch of hepatic artery, from celiac artery.
Jejunum and ileum: Superior mesenteric artery
All: Drains into portal venous system.
Sympathetic innervation: Celiac plexus and ganglia
Parasympathetic: Vagus nerve
What are the layers of the small intestine?
Mucosa, submucosa, muscularis, and serosa.
Where are brunner glands?
Auerbach plexdus?
Meissner plexus?
Brunner glands: Submucosa, secrete mucus and bicarbonate
Auerback: Between two layers of muscularis
Meissner plexus: Submucosa
What do Paneth cells do?
What do endocrine cells of the small intestine secrete?
Reside at base of crypts - eosinophilic secretory granules, contain lysozyme. Crypt defensins, and CD95 ligand. Mucosal defense.
Gastrin, secretin, CCK, glucagon, VIP, serotonin.
A newborn presents with vomiting of bile-containing fluid int he first day of life. Meconium is not passed. Pregnancy was notable for polyhydramnios.
Radiography detects a dilated fetal intestine filled with fluid.
Atresia: Complete occlusion of intestinal lumen. Could be thin intraluminal diaphragm, blind proximal/distal sacs, disconnected blind ends. Meconium ileus and cystic fibrosis involved.
Stenosis: Incomplete stricture, narrows but does not occlude lumen. Incomplete diaphragm possible cause.
A child is discovered with peptic ulceration. It is discovered that spherical and tubular structures are attached to the alimentary tract.
The structures have smooth muscle walls and gastrointestinal-type epithelium.
Duplications (enteric cysts).
Communicating duplications often form peptic ulcers.
A one-year-old patient presents with bleeding and intestinal obstruction.
A contrast radiograph shows a barium-filled outpouching of the ileum.
Meckel diverticulum - caused by persistence of vitelline duct.
Hemorrhage cuased by bleeding from peptic ulceration of ileum adjacent toectopic gastric mucosa.
Intestinal obstruction due to intussusception (lead point), or volvulus around vitelline duct remnant.
Diverticulitis: Inflammation of the diverticulum. Resembles appendicitis.
Perforation
Fistula: Fecal discharge from umbilicus may be observed.
A patient presents with malrotation. What is a concern you may have?
Bowel obstruction - anomalous attachments and bands, propensity for catastrophic volvulus of small and large intestine, inacrceration of bowel in an internal hernia.
A neonate who tested positive for cystic fibrosis presents with bowel obstruction. The first bowel movement has failed to occur.
Meconium ileus. Obstruction of small intestine by thickened tenacious meconium.
Complicated by volvulus, perforation, or intestinal atresia.
The toxigenic bacteria include…
V. cholerae and toxigenic strains of E. coli.
They cause diarrhea by secreting toxins. Damage to intestinal mucosa is minimal or abscent. Organism remains on mucosal surface. Causes watery diarrhea - dehydration.
The invasive bacteria include…
Shigella, Salmonella, certain strains of E. coli, Yersinia, and Campylobacter.
Directly injure the intestinal mucosa, tend to infect distal ileuma nd colon.
A patient presents with fever and hemorrhage.
The colon and terminal ileum is involved. A granular and hemorrhagic mucosa has many shallow serpiginous ulcers. Neutrophils accumulate in damage crypts, and lymphoid follicles of the mucosa break down to form ulcers.
Shigellosis.
A patient presents with fever and diarrhea. Ulcers are discovered in necrotic lymphoid tissue.
Black necrotic tissue mixed with fibrin.
Large basophilic macrophages filled with bacilli, erythrocytes, and necrotic debris. Resolves within a week.
Typhoid fever (Salmonella enteritis).
Feared complication: Intestinal hemorrhage and perforation.
A patient presents with fever and diarrhea. Mild ulceration, edema, and infiltration with neutrophils is found.
Nontyphoidal salmonellosis. Paratyphoid fever. Other strains besides S. typhi.
Hematogenous dissemination may cause bone, joint, or meninges infection. Sickle cell anemia patients develop osteomyelitis.
A patient returning from vacation has fever and bloody diarrhea.
Enteroinvasive, enteroadherent, and enterohemorrhagic strains of E. coli.
A patient presents with fever, cramps, and diarrhea.
Peyer patches are hyperplastic with ulceration of overlying mucosa. Fibropurulent exudate covers ulcers and contains many organisms.
Lymph nodes show epithelioid granulomas with central necrosis. Pets.
Yersinia enterocolitis. Granulomas formed by Y. pseudotuberculosis.
What are the most common infectious agents that cause food poisoning?
Staphylococcus aureus and clostridium perfringens.
Staph: Exotoxin. Diarrhea only.
Clostridium: Enterotoxin. Vomiting and diarrhea.
A hospitalized child develops diarrhea.
Rotavirus.
A patient presents with vomiting and diarrhea. He has patchy mucosal lesions and malabsorption in the upper small intestine.
Norwalk viruses.
A patient presents chronic abdominal pain. Endoscopy reveals circular ulcers in the transvers plane of the bowel. “Napkin ring” stricture of the bowel lumen is noted.
Mesenteric lymph nodes are enlarged with caseous necrosis. Granulomas found in all layers of the bowel walls. A history of drinking unpasturized milk is obtained.
Mycobacterium Bovis. Reactive fibrosis causes napkin ring strictures.
An immunocompromised patient presents with fungal invasion of the Gi tract.
Candidiasis, mucormycosis, histoplsamosis.
Protozoa that invade the small bowel include:
Giardia lamblia, Coccidia, and cryptosporidia.
Nematodes (roundworms) that invade the bowel include:
Ascaris, strongyloides, and hookworms.
Tapeworms that invade the small intestine include
Diphyllobothrium latum, Taenia solium, Taenia saginata, Hymenolepis nana.
Flukes that invade the small bowel include
Schistosomes and the giant intestinal fluke Fasciolopsis buski.
What bacterial infections cause minimal inflammatory changes on histology?
Vibrio cholerae
Toxigenic E. coli
Neisseria.
What bacterial infections cause acute self-limited colitis on histology?
Shigella
Campylobacter jejuni
Aeromonas
Salmonella
Clostridium difficile.
What bacterial infections cause pseudomembranous patterns on histology?
C. difficile
Shigella
Enterohemorrhagic E. coli.
What bacterial infections cause granulomas on histology?
Yersinia
Mycobacterium bovis
Mycobacterium avium-intracellulare
Actinomycosis.
What bacterial infections cause macrophage involvement on histology?
Whipple disease (Tropheryma whippeli)
M. avium-intracellulare.
What bacterial infections cause lymphocytes and macrophages on histology?
Lymphogranuloma venereum.
What bacterial infections cause architectural distortion on histology?
Salmonella typhimurium
Shigella.
