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Lower GI Pathology
Terms in this set (65)
TRUE or FALSE: The large intestine is longer than the small intestine
- Small intestine = 6 meters
- Large intestine = 1.5 meters
What part of the large intestine has the widest diameter?
RECALL: The small intestine is almost entirely supplied by what artery? What is the exception?
Superior Mesenteric A. (SMA)
Exception: Duodenum receives vessels from branches of the CELIAC A. as well
RECALL: What parts of the colon does the SMA supply?
Cecum/ascending colon/some of the transverse colon (WATERSHED area)
RECALL: What parts of the colon does the IMA supply?
Some of the transverse colon (WATERSHED area), descending colon, and the superior part of the rectum
What does the watershed area of the colon refer to?
Areas where they receive multiple blood supply (important when talking about ischemic disease)
- Example: Transverse colon
TEST: What are the four basic layers of the GI tract?
From DEEP (closest to lumen) to SUPERFICIAL (furthest from lumen
1) Mucosa: Epithelium, lamina propria, muscularis mucosa
2) Submucosa (w/ Meissner's plexus)
3) Muscularis propria (externa)
- With MYENTERIC (Auerbach's) plexus
The small intestine contains _____-associated _______ tissue, also known as _____, as well as unencapsulated _____ tissue in the lamina propria and submucosa known as _____ ______
The small intestine contains MUCOSA-associated LYMPHOID tissue, also known as MALT, as well as unencapsulated LYMPHOID tissue in the lamina propria and submucosa known as PEYER PATCHES
TEST: What major glands are located in the duodenal submucosa? What is the main function of these glands?
- Secretes ALKALINE fluid to neutralize any gastric acid that comes through!
Goblet cells are more associated with (large/small) intestine
_____ cells are more associated with the small intestine and terminal ileum and act as a first-line defense against bacteria
TEST: There is a ____ to ____ ratio in the mucosa of the small intestine that is not present in the large intestine
VILLI to CRYPT ratio in the mucosa of the small intestine (usually ~3)
In the large intestine, it really is all CRYPTS and hardly any villi
AGAIN/TEST: Meissner's plexus is located in which layer of the GI tract?
TEST/TEST: What are the five rule of 2s with _______ diverticulum?
- 2 inch long
- 2 feet from ileocecal valve
- 2% of the population
- Commonly presents in first 2 years of life
- May have 2 types of epithelia (gastric/pancreatic)
Hirschsprung disease is also known as ______ ______, characterized by the lack of _____ cells from both the _____ and ______ plexuses
Hirschsprung disease is also known as AGANGLIONIC MEGACOLON, characterized by the lack of GANGLION cells from both the MYENTERIC and MEISSNER plexuses
TEST/TEST: The most common cause of small bowel obstruction is what?
ADHESIONS ("You need to know this cold")
Definition: Fibrous BAND of scar tissue. commonly forms after surgery
Meconium plugs are associated with what disorder?
CYSTIC FIBROSIS (CFTR mutation, less Cl secretion, more intracellular Cl, Na, and H2O, extra thick mucus secretion and causes meconium plug to obstruct the intestine)
RECALL: Where is the most common place for intussusception to occur?
What are 3 main vascular diseases of the lower GI tract?
TEST: What is the hallmark of ischemia/infarction in the bowel?
HEMORRHAGE (and abdominal pain)
Ischemia of the bowel usually starts at the ______ layer
MUCOSAL layer (then goes mural, then transmural)
TEST: Preemies are especially prone to _______ _______ which is caused by ischemia of the intestinal mucosa
What are the two main types of causes of bowel ischemia? List some examples of each type of cause
- Hypoperfusion (heart failure, shock, DEHYDRATION, drugs, marathon)
- Bowel obstruction
- Arterial/venous thrombus or embolism
Angiodysplasia is essentially _____ veins of the bowel as it is a tortuous _____ of the vessels
Angiodysplasia is essentially VARICOSE veins of the bowel as it is a tortuous DILATION of the vessels
Where does angiodysplasia most often occur?
CECUM and RIGHT COLON
What are hemorrhoids?
DILATED or THROMBOSED veins in the hemorrhoid venous plexus
TEST: What are the two most frequent predisposing factors of hemorrhoids?
1) Strained defecation
TRUE or FALSE: Diarrhea is simply the presence of loose stool
FALSE, in order for stools to be considered diarrhea, it should be 3 or more loose stools per day
Diarrhea differs from dysentery in that the latter has (high/low) volume, is (painful/painless), and is (bloody/watery)
- LOW volume
What are the four types of diarrhea?
TEST: Define secretory diarrhea. Does it stop or persist with fasting?
>500 mL/day of ISOTONIC diarrhea that persist WITH FASTING
What are 3 common viral causes of secretory diarrhea?
What major bacterial enterotoxin causes "rice-water" stools (secretory diarrhea)? Briefly describe how this enterotoxin works.
CHOLERA toxin (from Vibrio cholerae)
Enterotoxin: Contains A-B subunits. B attaches to luminal epithelium, A enters the cells and triggers ADP-Ribosylation of the G-protein. This leads to an increase in cAMP, which will prevent Na absorption and promote Cl and HCO3 secretion, causing H2O to follow!
Excessive laxatives can cause (secretory/osmotic) diarrhea
TEST: Define osmotic diarrhea
Increased stool OSMOLALITY, can be caused by:
- Lactase deficiency (increase sugars in lumen, pulls water out)
- Bowel preps
- ANTACIDS (MgSO4)
TEST: Osmotic diarrhea differs from secretory diarrhea in that osmotic diarrhea (will/will not) stop with fastine
With secretory diarrhea, it will PERSIST even after FASTING
TEST: Define exudative diarrhea
PURULENT bloody stools
What are some bacterial species that cause exudative diarrhea?
- Campylobacter jejuni
- Entameba histolytica
Exudative diarrhea (stops/persists) with fasting
PERSISTS (just like secretory)
Malabsorptive diarrhea (stops/persists) with fasting
STOPS (just like osmotic)
- If you stop your intake of food, then defective intraluminal digestion will stop and the malabsorptive diarrhea will stop!
RECAP: Which two types of diarrhea will persist with fasting?
Secretory and Exudative
RECAP: Which two types of diarrhea will stop with fasting?
Osmotic and Malabsorptive
List some of the most common causes of malabsorption in the US
- Celiac sprue (disease)
- Pancreatic insufficiency
- Crohn's disease
- Infectious and non-infectious causes (cystic fibrosis for example)
Malabsorption is a disturbance in at least one of what four phases?
1) Intraluminal digestion
2) Terminal digestion
3) Transepithelial transport
4) Lymphatic transport
TEST: What are some other names for celiac disease?
- Celiac sprue
- Non-tropical sprue
- Gluten-sensitive enteropathy
BOARDS: List the two HLA associations with celiac disease
HLA-DQ2 and HLA-DQ8
What are the two parts that make up gluten?
TEST: Celiac disease is a sensitivity to not just gluten, but also ______
TEST: Celiac disease most commonly affects what parts of the intestinal tract?
- Distal DUODENUM
- Proximal JEJUNUM
TEST/TEST/BOARDS: List 3 types of antibodies found in the serum of patients with Celiac disease
1) Anti-endomysial (EMA)
2) Anti-tissue transglutaminase (TGA)
3) Anti-gliadin (AGA)
In celiac disease, there is progressive mucosal ______ with villous _______
Progressive mucosal ATROPHY with villous BLUNTING/FLATTENING
Tropical sprue is (infectious/non-infectious) cause of malabsorption
INFECTIOUS (commonly caused by E. coli or cyclospora, although no specific causal organism has been identified)
Which disaccharidase deficiency is by far the most common? What is the major symptom of this?
- Lactose can't be broken down into glucose and galactose, so it gets stuck in the intestinal lumen and the bacteria can constantly feed on them producing lots of GAS
In abetalipoproteinemia, there is an inability to make ______ from free fatty acids, resulting in deficiency in fat formation and thus fat-soluble vitamins such as what?
Inability to make CHYLOMICRONS from free fatty acids --> deficiency in FAT-SOLUBLE vitamins (A, D, E, K)
TRUE or FALSE: Bacterial toxins without the bacteria cannot cause enterocolitis
TRUE or FALSE: Cholera toxin causes bloody diarrhea
TEST: Which two strains of E. coli does NOT produce toxins?
1) EIEC (only invades)
2) EPEC (attaches to apical surface and flattens the epithelium)
TEST/TEST: C. difficile causes what major GI pathology?
TEST/TEST: Whipple's disease is caused by an infection with ______ ______, most commonly to _____ in the (proximal/distal) intestinal lamina propria and ______ lymph nodes
Whipple's disease is caused by an infection with TROPHERYMA WHIPPELI, most commonly to MACROPHAGES in the PROXIMAL intestinal lamina propria and MESENTERIC lymph nodes
TEST/TEST: Whipple's disease is fatal without ______ treatment
TEST/TEST/BOARDS: Whipple's disease stains positive with _____ stain for _____ _______
Whipple's disease stains positive with PAS stain for FOAMY MACROPHAGES
TEST/TEST: Flask-shaped ulcerations in the colon point to what protozoan?
TEST: List some of the main differences between Crohn's (CD) and ulcerative colitis (UC)
1) Layers of GI tract affected
- UC: Mucosa and submucosa only
- CD: Transmural
- UC: COLON only, CONTINUOUS (no skip areas)
- CD: Any part of GI tract w/ SKIP areas, commonly in TERMINAL ILEUM
- UC: Prevents it
- CD: Increases risk of it
- UC: Toxic megacolon and cancer
- UC: Bloody
- CD: Less frequently bloody
- UC: Not used unless surgery
- CD: Used if fistula occurs
- UC: Curable
- CD: Incurable (incidences of relapses)
AGAIN: Crohn's disease usually affects what layers of the GI tract?
ALL LAYERS (transmural)
AGAIN: Ulcerative colitis will never show up in the (small/large) intestine
SMALL (limited to COLON)
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