GI General Flashcards
How long does it take for food to get from your mouth to the bottom of the esophagus?
10 seconds
How long does it take for food to get from your mouth to exit the stomach?
1-3 hours
How long does it take for food to get from your mouth to the end of the small intestine?
7-9 hours
How long does it take for food to get from your mouth to the large intestine?
25-30 hours
How long does it take for food to get from your mouth to excretion?
3-5 days (30-120 hrs)
What are the modalities for GI regulation?
endocrine-stimuli associated with meal
neurocrine- connections to CNS and enteric nervous system
paracrine- local mediators
What happens when the parasympathetic nerves (enteric neurons) are stimulated?
cause general increase in activity of entire enteric nervous system which enhances GI functions
What happens when the sympathetic nerves in GI tract are stimulated?
inhibition of activity in GI tract
inhibition of smooth muscle fn
excitation/contraction of sphincters
Actions of Ach in GI function
contraction of smooth muscle in wall relaxation of sphincters ↑ salivary secretion ↑ gastric secretion ↑ pancreatic secretion
Actions of NE in GI function
relaxation of smooth muscle in wall contraction of sphincters
↑ salivary secretion
Actions of vasoactive intestinal peptide (VIP) in GI function
relaxation of smooth muscle
↑ intestinal secretion
↑ pancreatic secretion
Action of gastrin-releasing peptide (GRP) in GI function
↑ gastrin secretion
Stimulus for gastrin release
and site of production
AA and stomach distension
↓ with low pH
site: stomach
simuli and site of production for cholecystokinin
AA/FA
site: small intestine
simuli and site of production for secretin
H+/FA
site: small intestine
simuli and site of production for GIP
AA/FA/carbs
site: small intestine
simuli and site of production for motilin
↓ with feeding
site: small intestine
Macronutrients → absorptive units
carbohydrates →
proteins →
lipids →
carbohydrates →monosaccharides (glucose, fructose, galactose)
proteins → di and tri-peptides
lipids → monoglycerides and fatty acids
What do pepsins (pepsinogens) digest and how are they activated?
proteins and polypeptides
activated by HCl in the stomach
What does enteropeptidase/enterokinase digest and where is it excreted?
tyrpsinogen
excreted: intestinal mucosa
What does trypsin (tyrpsinogen) digest and how is it activated?
proteins and polypeptides
activated by enteropeptidase/enterokinase in exocrine pancreas
What does collipase (procolipase) digest and how is it activated?
fat droplets
activated by trypsin in exocrine pancreas
What does pancreatic lipase digest and where does it come from?
triglycerides
comes from exocrine pancreas
What does pancreatic amylase digest and how is it activated?
starch
activated by Cl- in exocrine pancreas
Where is iron and calcium absorbed?
duodenum
where are carbohydrates absorbed?
upper part of small intestine
where are fats and proteins absorbed?
throughout small intestine
where are bile salts and vitamin B 12 absorbed?
ileum
What is receptive relaxation?
the act of swallowing causes neurotransmitters too send signals to relax lower esophageal sphincter and stomach fundus
Define achalasia
inability of LES to relax during swallowing
What anatomical dysfunction allows for gastric reflux to occur
↓ LES tone
What is stimuli for gastrin release?
what is its effect?
inhibitory stimuli?
small peptides, AA, stomach distention, vagal stimulation-GRP
effect: H+ secretion
inhibitory-secretin H+ feedback loop
Rank rate of gastric emptying from slowest to fastest for proteins, carbs and fats
fat < protein < carb
Gastric pressures seldom rise above the levels that breach the lower esophageal sphincter even when the stomach is filled with a meal due to what process?
receptive relaxation
What is the major function of the duodenum?
neutralization to inactivate pepsin
biliary secretion
pancreatic secretion
What cells secrete secretin and why?
S cells of duodenum stimulated by H+ and fatty acids to increase pancreatic secretions of bicarb
What cells secrete cholecystokinin and why?
I cells of duodenum and jejunum stimulated by fatty acids and AA to increase pancreatic secretions and stimulate gallbladder to contract and inhibit gastric emptying
What is the 3rd MC cancer of internal organs?
carcinoma of large intestine
What is fn of fenestrated endothelium?
lines capillary sinusoids and provides easy access of nutrient delivery to hepatocytes
What is the fn of Kupffer cells within capillary sinusoids?
uniquely positioned to remove bacterial toxins coming from gut and to clear circulating Ag-Ab complexes
What is the function of Stellate cells within space of Disse?
fibroblasts activated to myofibroblasts
store Vit A
produce collagen, impt in scar formation during liver damage
What does LFT consist of?
bilirubin, albumin
Add: prothrombin time
What is included in hepatic panel?
bilirubin AST ALT AlkP Albumin Prothrombin time
If a patient is treated with a broad-spectrum antibiotic for several days or more, what might happen to the color of the stool – and why?
lighter bc bacteria are not there to conjugate bilirubin
What happens to albumin with liver injury?
decreases
What happens to prothrombin time with liver injury
increases
What clotting factors are affected by the liver?
1, 2, 5, 7, 9, 10
What is HL of albumin?
HL of prothrombin time?
albumin 20 days
prothrombin time ~6 hours
What happens to AST and ALT with liver injury?
increases
ALT>AST in most cases of liver inj
If alcohol related inj, cirrhosis /malnutrition or sudden acute liver necrosis → AST>ALT
What is HL of AST?
HL of ALT?
AST 8 hrs (mitochondrial AST is 10 days)
ALT 48 hrs
What enzyme do we use to evaluate the biliary tract?
What is its HL?
alkaline phosphatase (AlkP)
HL 7 days
can also arise from bone, placenta, reticuloendothelial cells, intestine, kidney
What tests do you use to detect cholestasis?
bilirubin
alkP
GGT
What is jaundice usually due to?
hepatobiliary disease
If urine is dark like tea what can it be?
blood (hemolysis)- if unconjugated bili
direct bilirubin- if conjugated (obstruction)
What are causes of ↑ unconjugated bilirubin?
↑ RBC degradation
↓ albumin-bilirubin binding
↓ Hepatocyte internalization
↓ bilirubin conjugation (gilbert’s disease)
What are causes of ↑ conjugated bilirubin?
↓ bilirubin excretion from liver-
cholestasis
What causes increase in peritoneal fluid in cirrhosis?
low albumin
high portal HTN
renal retention
INC renin causing Na retention
What is Child’s A for liver cirrhosis severity?
no abnormal parameters
~40 mos survival
What is Child’s B for liver cirrhosis severity?
1-2 abnormal parameters
~32 mos survival
What is Child’s C for liver cirrhosis severity?
> 2 abnormal parameters
~8 mos survival
What parameters are considered for child-pugh’s severity score for cirrhosis?
encepalopahty ascites bilirubin albumin prothrombin ratio
When is patient considered for liver transplant with cirrhosis?
when they have approximately <1 yr survival
What is MELDs score based on?
serum creatinine
bilirubin
INR prothrombin time
<10 is >1 yr survival
11-25 50% 1 yr survival
>25 <1 yr survival
What are contraindications to liver transplant?
systemic infection or AIDS (HIV alone is not an absolute contraindication)
severe cardiopulmonary disease
metastatic malignancy
What are the 3 criteria for the histopath grade of chronic hepatitis?
- Amount of lymphocytic infiltrate
- Amount of lobular necrosis and apoptotic bodies
- Amount of periportal necrosis
What is the best gauge of diarrhea?
stool mass (>250 g)
also 70-95% water
>2x daily
What is the foregut composed of?
pharynx, esophagus, stomach, respiratory tract
What is the midgut composed of?
small intestine, primordium of liver and pancreas
What is the hindgut composed of?
colon
What does the Salivary Gland secrete and what is its fn?
Amylase
Fn: Digestion of starch
What does the stomach secrete and what is its fn?
Pepsin & HCL→digest proteins
Gastrin Intrinsic Factor →mediates absorption of vit B12
What does the small intestine secrete and what is its fn?
Enterokinase →activates pancreatic enzymes
Cholecystokinin →Stimulates GB contraction &pancreatic secretion of bicarbs
Secretin→Stimulates secretion of pancreatic trypsin and chymotrypsin
The 3‐cm segment of proximal esophagus at the level of the cricopharyngeus muscle (15 to 18 cm from the incisors) is referred to as the
upper esophageal sphincter
The 2‐ to 4‐cm segment just proximal to the anatomic GEJ (at 36 to 40 cm from the incisors), at the level of the diaphragm, is referred to as the
lower esophageal sphincter
Dysphagia
difficulty swallowing
What is the MC benign salivary gland tumor
Pleomorphic Adenoma
What is the MC malignant salivary gland tumor
Mucoepidermoid Carcinoma
What is MC type of carcinoma in upper and middle esophagous?
lower?
U & M = SCC
lower= adenocarcinoma
How is insulin produced?
by β-cells in pancreatic islets as proinsulin → cleaved to insulin and inactive C-peptide
How much does Hgb A1c increase for every 30 mg/dL rise in serum glucose?
1%
Difficulty transferring food from the mouth to the upper esophageal sphincter
Oropharyngeal dysphagia
Difficulty with the passage of ingested material from the hypopharynx to the stomach
Esophageal dysphagia
Painful swallowing
odynophagia
What does odynophagia usually represent?
inflammatory process
Effect of H. pylori infection in duodenal antrum
increased gastric acid secretion from G cells which can cause gastric metaplasia in the duodenal bulb and colonization of these islands by H pylori leads to duodenitis or duodenal ulcers
Effect of H. pylori infection in gastric body
decreased acid secretion as the chronic inflammation overwhelms the gastric mucosal defense mechanisms
What is required for fat absorption?
emulsification
What is the principal digestive enzyme in the stomach?
What activates it?
What are substrates?
Enzyme- pepsins (pepsinogens)
Activator- HCl
Substrates- Proteins and polypeptides
What is the principal digestive enzyme in the intestinal mucosa?
What are substrates?
Enzyme- nteropeptidase/ enterokinase
Substrates-Trypsinogen
What are the pancreatic digestive enzymes
Trypsin (trypsinogen)
Colipase (procolipase)
Pancreatic lipase
Pancreatic lipase
Activator and substrates for Trypsin (trypsinogen)
Activator- Enteropeptidase/ enterokinase
Substrates- Proteins and polypeptides
Activator and substrates for Colipase (procolipase)
Activator- Trypsin
Substrates- Fat droplets
Substrates for Pancreatic lipase
Substrates- Triglycerides
Activator and substrates for Pancreatic -amylase
Activator- Cl-
Substrates- Starch
What does Migrating Motor Complex (MMC) do?
During fasting, sweeps periodically along the length of the stomach and small
intestine to clear them of undigested residues
What is bile acid composed of?
Cholic acid and chenodeoxycholic acid
What are micelles?
detergents formed by bile acids that emulsify the products of lipid digestion so fats can be absorbed
What stimulates the gallbladder to contract after a meal?
CCK (also causes relaxation of sphincter of Oddi)
Color of biliverdin?
unconjugated bilirubin?
biliverdin- green
unconjugated bilirubin- yellow
What causes neonatal jaundice?
↓ UDP glucuronyl transferase
Where does absorption of nutrients and electrolytes occur?
secretion?
abs- SI at villus tip (NaCl, nutrients)
sec- crypt (Cl-)
water follows Cl-
What intestinal immunity defense do we have against GI infection?
Secretory IgA: lamina propria plasma cells
Mucosa-associated lymphoid tissue (MALT): Peyer’s patches
Phagocytes
Enterotoxins
direct effect on intestinal mucosa to elicit net fluid & electrolyte secretion
Increased production of cAMP or cGMP
Classic = cholera toxin, E. coli LT and ST toxins
Cytotoxins
mucosal destruction
Shiga toxin” – E. coli
Shigella dysenteriae
Clostridium difficile toxin B
Neurotoxins
pre-formed toxins
Act on autonomic nervous system
Acute N/V/D within hours of ingestion
“Food poisoning” by Staph aureus, Bacillus cereus, Clostridium botulinum
What bacteria has ability to adhere to and colonize mucosa
E. coli
What bacteria invade and destroy epithelial cells?
Shigella, Salmonella
What tests are true measures of liver function, becoming abnormal when liver cell function is impaired?
Bilirubin
Albumin
Prothrombin Time
When is Unconjugated bilirubin increased?
hemlysis
When is conjugated bili increased?
hepato-biliary disease
What happens to albumin with liver inj?
PT time?
albumin decreases
PT increases
When do alanine(ALT) aspartate(AST) increase?
injury to hepatocyte membrane allows release
What is the only abnormality in majority of persons with liver disease?
Elevated liver enzymes
What causes jaundice?
bilirubin excess
visible in adults > 2x normal
Visable in neonates > 5x normal
What happens to urine and stool with hepatobiliary disease?
dark tea colored urine (urine bilirubin)
light stools (no stool pigments unless bilirubin reaches gut)
What causes Cholestasis
static bile flow, due to biliary obstruction or hepatocyte loss of function
What is the preferred site of absorption of iron and folate?
Duodenum
Where does > 90% of nutrient absorption occur?
Jejunum
Where is the site of vitamin B12 and bile salt absorption?
Ileum
What are Manifestations of Malabsorption?
Abdominal distension, flatulence Anemia Kidney stones Peripheral neuropathy Bone pain, osteomalacia, fractures dermatitis
What happens instead of losing carbs that are malabsorbed?
absorbed in the colon as short chain fatty acids
What occurs as a result of Small Ileal Resection?
Fat Malabsorption
Significant bile malabsorption
Result is secretory diarrhea
How do you test for CHO Malabsorption?
Malabsorbed CHO reaches intraluminal bacteria and H2 is produced, absorbed and measured in exhaled air
How do you test for SBBO?
Lactulose is ingested (non-absorbable CHO) to test for SBBO. Excess H2 is exhaled and measured
