Chapter 13: GI Small Intestine Structural and Infections

Question 1

What are the plicae circularis and peyer patches?

Answer 1

Plicae circularis: Spiral folds of mucosa and submucosa.

Peyer patches: Lymphoid aggregates in submucosa.

Question 2

Describe vascular and neurologic innervation of the small intestine.

Answer 2

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

Question 3

What are the layers of the small intestine?

Answer 3

Mucosa, submucosa, muscularis, and serosa.

Question 4

Where are brunner glands?
Auerbach plexdus?

Meissner plexus?

Answer 4

Brunner glands: Submucosa, secrete mucus and bicarbonate

Auerback: Between two layers of muscularis

Meissner plexus: Submucosa

Question 5

What do Paneth cells do?

What do endocrine cells of the small intestine secrete?

Answer 5

Reside at base of crypts - eosinophilic secretory granules, contain lysozyme. Crypt defensins, and CD95 ligand. Mucosal defense.

Gastrin, secretin, CCK, glucagon, VIP, serotonin.

Question 6

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.

Answer 6

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.

Question 7

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.

Answer 7

Duplications (enteric cysts).

Communicating duplications often form peptic ulcers.

Question 8

A one-year-old patient presents with bleeding and intestinal obstruction.

A contrast radiograph shows a barium-filled outpouching of the ileum.

Answer 8

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.

Question 9

A patient presents with malrotation. What is a concern you may have?

Answer 9

Bowel obstruction - anomalous attachments and bands, propensity for catastrophic volvulus of small and large intestine, inacrceration of bowel in an internal hernia.

Question 10

A neonate who tested positive for cystic fibrosis presents with bowel obstruction. The first bowel movement has failed to occur.

Answer 10

Meconium ileus. Obstruction of small intestine by thickened tenacious meconium.

Complicated by volvulus, perforation, or intestinal atresia.

Question 11

The toxigenic bacteria include…

Answer 11

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.

Question 12

The invasive bacteria include…

Answer 12

Shigella, Salmonella, certain strains of E. coli, Yersinia, and Campylobacter.

Directly injure the intestinal mucosa, tend to infect distal ileuma nd colon.

Question 13

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.

Answer 13

Shigellosis.

Question 14

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.

Answer 14

Typhoid fever (Salmonella enteritis).

Feared complication: Intestinal hemorrhage and perforation.

Question 15

A patient presents with fever and diarrhea. Mild ulceration, edema, and infiltration with neutrophils is found.

Answer 15

Nontyphoidal salmonellosis. Paratyphoid fever. Other strains besides S. typhi.

Hematogenous dissemination may cause bone, joint, or meninges infection. Sickle cell anemia patients develop osteomyelitis.

Question 16

A patient returning from vacation has fever and bloody diarrhea.

Answer 16

Enteroinvasive, enteroadherent, and enterohemorrhagic strains of E. coli.

Question 17

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.

Answer 17

Yersinia enterocolitis. Granulomas formed by Y. pseudotuberculosis.

Question 18

What are the most common infectious agents that cause food poisoning?

Answer 18

Staphylococcus aureus and clostridium perfringens.

Staph: Exotoxin. Diarrhea only.

Clostridium: Enterotoxin. Vomiting and diarrhea.

Question 19

A hospitalized child develops diarrhea.

Answer 19

Rotavirus.

Question 20

A patient presents with vomiting and diarrhea. He has patchy mucosal lesions and malabsorption in the upper small intestine.

Answer 20

Norwalk viruses.

Question 21

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.

Answer 21

Mycobacterium Bovis. Reactive fibrosis causes napkin ring strictures.

Question 22

An immunocompromised patient presents with fungal invasion of the Gi tract.

Answer 22

Candidiasis, mucormycosis, histoplsamosis.

Question 23

Protozoa that invade the small bowel include:

Answer 23

Giardia lamblia, Coccidia, and cryptosporidia.

Question 24

Nematodes (roundworms) that invade the bowel include:

Answer 24

Ascaris, strongyloides, and hookworms.

Question 25

Tapeworms that invade the small intestine include

Answer 25

Diphyllobothrium latum, Taenia solium, Taenia saginata, Hymenolepis nana.

Question 26

Flukes that invade the small bowel include

Answer 26

Schistosomes and the giant intestinal fluke Fasciolopsis buski.

Question 27

What bacterial infections cause minimal inflammatory changes on histology?

Answer 27

Vibrio cholerae

Toxigenic E. coli

Neisseria.

Question 28

What bacterial infections cause acute self-limited colitis on histology?

Answer 28

Shigella

Campylobacter jejuni

Aeromonas

Salmonella

Clostridium difficile.

Question 29

What bacterial infections cause pseudomembranous patterns on histology?

Answer 29

C. difficile

Shigella

Enterohemorrhagic E. coli.

Question 30

What bacterial infections cause granulomas on histology?

Answer 30

Yersinia

Mycobacterium bovis

Mycobacterium avium-intracellulare

Actinomycosis.

Question 31

What bacterial infections cause macrophage involvement on histology?

Answer 31

Whipple disease (Tropheryma whippeli)

M. avium-intracellulare.

Question 32

What bacterial infections cause lymphocytes and macrophages on histology?

Answer 32

Lymphogranuloma venereum.

Question 33

What bacterial infections cause architectural distortion on histology?

Answer 33

Salmonella typhimurium

Shigella.