Path of the Lower GI Tract -Mesa Flashcards
What is the blood supply to the small intestine (other than the duodenum)?
SMA
What supplies the duodenum?
pancreaticoduodenal A from the Celiac A
What supplies the colon from the cecum to the splenic flexure? Splenic flexure to the rectum?
- cecum to the splenic flexure: SMA
- Splenic flexure to the rectum: IMA
Which areas of the colon are susceptible to ischemia?
Watershed areas (Marginal A) and the distal sigmoid (pudendal and superior rectal AA)
Where are rings of kerckring (plicae) found?
small intestine
What are the 4 layers of the small intestine?
- Mucosa: epithelium, lamina propria, muscularis mucosa
- Submucosa: loose connective tissue, Meissner’s plexus
- Muscularis Propria: inner circ., outer long.
- Serosa: fibroelastic tissue, mesothelium
Where are the Brunner’s glands found?
duodenal mucosa only
What is the Rule of 2’s associated with Meckel’s diverticulum?
2 inches long, 2 feet from ileocecal valve, 2 times as common in males than females, 2% of population, 2% symptomatic, 2 types of ectopic tissue: gastric and pancreatic
What is Hirschsprung Disease?
- aganglionic megacolon
- failure of neural crest cells to migrate tot he colon –> lack of parasympathetic ganglionic cells –> functional obstruction and colonic dilation proximal to affected segment (can get toxic mega colon)
-plain film radiograph may reveal marked colonic dilation proximal to effected bowel segment
What is the most common cause of bowel obstruction?
Adhesions (due to previous surgeries)
What segment of the colon is most susceptible to volvulus?
Sigmoid colon
What are the 2 types of causes of ischemia/infarction?
- non-occlusive (hypoperfusion–> shock, drugs, marathon runner)
- occlusive (arterial/venous thrombus or embolism, iatrogenic)
What are the most frequent predisposing factors of hemorrhoids?
- strained defecation and pregnancy
- other: portal HTN and neoplasms
How does dysentery differ from diarrhea?
- dysentery is low volume, painful, bloody diarrhea
- diarrhea=inc in stool mass, frequency or fluidity (>3 + loose stool/day)
What are the characteristics of secretory diarrhea? What are the causes of secretory diarrhea?
->500mL/day, isotonic, persistent with fasting
- Viral damage to mucosa (Rotavirus, Norovirus, Adenovirus)
- Enterotoxins, bacterial (V. cholera, E. coli, B. cereus, C. perfringens)
- Neoplasms secreting GI hormones
- Excessive laxatives
What are the potential causes of osmotic diarrhea? How does it respond to fasting?
- Increased stool osmolality
- Disaccaridase (lactase) deficiency
- Bowel preps
- Antacids, egs., MgS04
-Abates with fasting
What are the characteristics of exudative diarrhea? What causes it?
-purulent bloody stools, persists with fasting
- Bacterial damage to GI mucosa (Shigella, Salmonella, C. jejuni, E. histolytica)
- IBD
- Typhilitis (Caecitis, immunosuppression colitis), chemo, AIDS, kidney transplant
What are the most common causes of malabsorption diarrhea? Where can the disturbances take place?
- celiac sprue
- Pancreatic insufficiency
- Crohn’s
disturbances:
- Intraluminal digestion
- Terminal digestion
- Transepithelial transport
- Lymphatic transport
What is Celiac Disease? What HLA is associated with it?
sensitivity ot gluten–> perpetual inflammation and progressive mucosal atrophy and villous flattening
HLA-DQ2 and DQ8
What is the most common disaccaridase deficiency? What are the different types?
- Lactase*
- types: congenital (rare, mutation for lactase gene) and acquired (down regulation of lactase gene expression)
What is Abetalipoproteinemia?
- mutation in MTtP gene –> inability to make chylomicrons from FFAs and monoglycerides
- deficiencies in Vit A, D, E, K
- acanthocytes (Burr cells) because can’t make cell membranes
What are the 3 ways you can get bacterial enterocolitis?
- ingestion of bacterial toxins (staph, vibrio, clostridium)
- ingestion of bacteria which produce toxins (traveller’s diarrhea, E. coli)
- Infections by enteroinvasive bacteria (EIEC, shigella, C. diff)
Which pathogen can cause dysentery with a low inoculum and i passed person to person?
Shigellosis (salmonella is not bloody)
What are the different types of E. coli and how do they affect people?
- Enterotoxigenic: traveller’s diarrhea, non-invasive, toxins
- Enterohemorrhagic: O157:H7, non-invasive and toxins
- Enteroinvasive: invasion of epithelium and NO toxins
- enteroaggregative: adhere to brush border and produces toxins
