Ch 17: GI Tract Flashcards
what are the two types of organs of the digestive system
ailmentary canal organs
accessory organs
what do acessory organs do
assist in digestive but have no direct contact with food
what are 5 examples of accessory organs
teeth
tongue
salivary glands
pancreas
gallbladder
what two things are absorbed in the stomach
water
alcohol
what are the three main things absorbed in the duodenum
iron
calcium
fats
what are the two things absorbed in the jejunum
sugars
proteins
what are two things absorbed in the ileum
bile salts
vitamin B12
what are three things absorbed in the colon
water
electrolytes
vitamin K
the sympathetic nervous system provides innervation to the GI tract through which nerves
splanchnic nerves
the parasympathetic nervous sytem innervates the GI tract through which nerve
vagus nerve
what are the two plexi of the enteric nervous system
myenteric (auerbach) plexus
submucosal (meissner) plexus
where is the myenteric (auerbach) plexus located
muscularis externa (propria)
where is the meissner plexus
within the submucosa
what is malaborption syndrome
defective absorption of fats, vitamins, proteins, carbs, electrolytes, minerals, and water
what causes malabsorption syndrome
disturbance in one of four phases of nutrient absorption
what are the four phases of nutrient absorption
intraluminal digestion
terminal digestion
transepithelial transport
lymphatic transport
celiac disease, a type of malabsorption syndrome, is caused by defects in which two phases of nutrient absorption
terminal digestion
transepithelial transport
disaccharidase deficiency, a type of malabsorption syndrome, is caused by defects in which phase of nutrient absorption
terminal digestion
inflammatory bowel disease, a type of malabsorption syndrome, is caused by defects in which three phases of nutrient absorption
intraluminal digestion
terminal digestion
transepithelial transport
what is celiac disease (celiac sprue/gluten sensitive enteropathy)
immune mediated disorder triggered by ingestion of gluten like wheat, rye, or barley
what genetic component is involved in celiac disease
mutations in:
HLA-DQ2
HLA-DQ8
what are three characteristics of celiac disease
intraepithelial lymphocyte activation
loss of absorptive villi
crypt hyperplasia (crypts get deeper)
explain the celiac sprue mechanism
gliadin causes epithelial cells to make IL-15
IL-15 causes proliferation of cytotoxic T cells that express NKG2D receptors
stress causes enterocytes to express surface MIC-
A
cytotoxic T cells destroy enterocytes
damage allows passage of other gliadin peptides
gliadin has amino group removed by a transglutaminase
deaminated gliadin binds to HLA(DQ2 or DQ8) on APC to activate helper T-cells
helper T cells release IFNy and activate B cells
B cells make antibodies which cause tissue damage
what are some clinical manifestations of celiac disease
diarrhea
bloating
fatigue
anemia - malabsorption of iron/vitamin B12
dermatitis herpetiformis
what is dermatitis herpetiformis
itchy, blistering skin lesions seen in 10% of those with celiac disease
what is hirschsprung disease
a birth defect characterized by the absence of the intramural neural plexus (ganglion cells) in the distal colon which causes a blockage
what is another name for hirschsprung disease
congenital aganglionic megacolon
hirschsprung disease is associated with what other disease
down syndrome
who, males or females, are most affected by hirschsprung disease
males
if in females, aganglionic segment is longer
what is the mechanism of hirschsprung disease
mutation in tyrosin kinase causes failure of ganglion cells of the Meissner and auerbach plexuses to migrate to wall of rectum or they undergo premature death
both lead to loss of peristaltic contractions
where will you see dilation in hirschprung disease
proximal to the affected segment cause everything backs up
what portion of colon is always affected in hirschsprung disease
rectum
what are the clinical mainfestations of hirschsprung disease
can’t pass meconium after birth
leads to abdominal distention and bilious vomit
what are the 4 complications of hirschsprung disease
enterocolitis
fluid and electrolyte disturbances
perforation
peritonitis
what is an aquired megacolon
abnormal dilation and enlargment of the colon due to underlying conditions that affect the colon’s ability to move stool efficiently
what is the main symptom of chagas disease
acquired megacolon - dilation of colon
which two bugs cause chagas disease which leads to aquired megacolon
kissing bug
trypansoma cruzi parasite
what is inflammatory bowel disease (IBD)
group of diseases that are characterized by chronic inflammation of the GI tract
who are most at risk for IBD
young people in teens and 20’s
caucasians
what are the two main types of IBD
crohn disease
ulcerative colitis
which part of the bowel is affected in both crohn and ulcerative colitis
crohn: ileum, ICV, and cecum
ulcerative colitis: colon and rectum
what is the distribution like of crohn and ulcerative colitis
crohn: skip lesions
ulcerative colitis: diffuse
do crohn and ulcerative colitis have strictures
crohn: yes
ulcerative colitis: rare
what is the wall appearance of crohn and ulcerative colitis
crohn: thickened
ulcerative colitis: normal
what is the inflammation pattern of crohn and ulcerative colitis
crohn: transmural (entire thickeness)
ulcerative colitis: mucosa and submucosa
what are the ulcers like in crohn and ulcerative colitis
crohn: deep, knife like
ulcerative colitis: superficial
do crohn and ulcerative colitis have granulomas
crohn: yes, noncaseating
ulcerative colitis: no
do crohn and ulcerative colitis have malabsorption
crohn: yes
ulcerative colitis: no
do crohn and ulcerative colitis have malignant potentials
crohn: if colon invovlement, yes
ulcerative colitis: yes
do crohn and ulcerative colitis have toxic megacolon
crohn: no
ulcerative colitis: yes
what is the mechanism of IBD
interactions between gut microbes and immune system in predisposed individuals leads to improper mucosal immune activation
what are the three genetic and environmental elements that contribute to IBD
altered mucosal immunity
defects in autophagy and cellular stress response
host microbial interactions
what is an example of altered mucosal immunity leading to IBD
helper T17 cells expand in diseased intestine
what are two gene examples of defects in autophagy and cellular response which leads to IBD
mutations in:
ATG16L1
IRGM
what percentage of crohn disease cases affect the small intestine (ileum)
40%
what percentage of crohn disease cases affect the small intestine and colon
30%
what percentage of crohn disease cases only involve the colon
30%
which disease can be characterised by irregular cobblestone appearance of mucosa
crohn disease
what are three things that can trigger reactivation of crohn disease
physical emotional stress
specific dietary items
smoking
which disease is characterized by slightly red and granular colonic mucosa with a line of demarkation
ulcerative colitis
what is toxic megacolon
dilation of the colon due to inflammation of muscularis propria and neuromuscular dysfunction
what are three clinical manifestations of ulcerative colitis
blood diarrhea with string mucoid material
lower abdominal pain
cramps relieved by defecation
