19a) GI function Flashcards
function of sphincters
Serve to compartmentalize the gut
3 major stomach regions
Cardiac (with fundus)
Body
Pylorus
cardiac/fundus region secretions
mucus
group II pepsinogens
body stomach region secretions
mucus (surface epis)
HCl (parietal)
IF (parietal)
groups I and II pepsinogens (chief)
serotonin (enterochromaffin)
areas of pylorus
Antrum
Pyloric canal
Sphincter
pyloric region secretions
Mucus
Group II pepsinogen
Serotonin
Gastrin
Other hormones
only stomach site of HCl
body
surface epi/goblet cells secrete…
mucus
parietal cells secrete…
HCl
IF
chief cells secrete…
groups I and II pepsinogen
enterochromaffin cells secrete…
serotonin
delivers bile and enzymes into the duodenum
Pancreaticobiliary duct
Nerves located in the gut wall assist in controlling…
propulsion and fluid regulation
Involuntary control of GI activities for each region are modulated via …
extrinsic neural inputs
2 principal GI functions
Assimilation of nutrients
Elimination of waste
sterilizes upper gut
gastric acid
Distal stomach has … to propel solid food against the pylorus
phasic contractions
contents of pancreatic juice
digestive enzymes
bicarbonate
——- absorbs vitamin B12 and bile acids
ileum
Small intestines help in waste elimination by removing bile from…
erythrocyte degradation
toxins metabolized
unaltered medications
cholesterol
terminal end of SI
ileocecal junction
Stool is dehydrated by…
colonic mucosa cells
Fermentation of …. in colon by bacterial colonization
undigested carbs and short-chain fatty acids
GI regulatory peptides influence…
- Motility
- Secretion
- Digestion
- Absorption
- Bile flow and secretion of pancreatic hormones
- Vascular wall tonicity, blood pressure, and cardiac output
main 5 gastric regulatory peptides
- Cholecystokinin
- Gastrin
- Secretin
- Vasoactive intestinal polypeptide
- Glucose-dependent insulinotropic peptide (gastric inhibitory polypeptide)
Linear polypeptide with multiple molecular forms
CKK
CKK
cholecystokinin
from I cells of the upper small intestinal mucosa
CKK
CKK functions
- Regulates gallbladder contractions
- Increases motility
- Stimulates gastric HCL and pepsinogen secretion
- Pancreatic bicarbonate secretion
- Pancreatic growth
- Relaxation of the sphincter of Oddi
- Secretion from duodenal glands
- Regulating appetite
Formed after cleavage of a single precursor (———–) which contains 101 amino acids
Molecular forms include big, little, and mini
gastrin
preprogastrin
from endocrine cells (G cells) of the antral mucosa
gastrin
gastrin functions
- Stimulates release of gastric acid in the stomach
- Promotes the secretion of pepsinogen and intrinsic factor (IF)
- Stimulates release of secretin by the small intestine
gastrin released in response to…
- Antral distention (stomach stretching)
- Amino acids, peptides, and polypeptides from partially digested proteins in the stomach
also…
Alcohol
Caffeine
Insulin-induced hypoglycemia
Infusion of calcium
Stimulation of the vagus nerve caused by smelling, tasting, chewing, and swallowing food
from granular S cells located primarily in the duodenum
secretin
secretin function
- Stimulates the pancreas to secrete an increased volume of fluid with high bicarbonate content
- Stimulates PTH
- Inhibits gastrin secretion
- Reduces motility
- Reduces insulin
VIP
Vasoactive Intestinal Polypeptide
secretin released in response to…
gastric HCL coming into contact with S cells
neurotransmitter from nervous system and gut
short duration of action
VIP
VIP functions
- Vasodilation and relaxation of smooth muscles of the circulatory and genitourinary systems and the gut
- Increase water and electrolyte secretion from the pancreas and gut
- Release of hormones from the pancreas, gut, and hypothalamus
- Inhibition of gastrin and gastric acid secretion
- Stimulation of lipolysis, glycolysis, and bile flow
GIP
Glucose-Dependent Insulinotropic Peptide
Gastric Inhibitory Polypeptide
from K cells located in the duodenal and jejuna mucosa
GIP
GIP levels are increased by …
oral administration of glucose and triglycerides
intraduodenal infusion of solutions containing a mixture of amino acids
GIP functions
- Stimulates insulin secretion (insulinotropic)
- Increases intestinal fluid and electrolyte secretion
- Inhibits gastric acid, pepsin, and gastrin secretions
characteristics of Zollinger-Ellison
- fulminate peptic ulcers
- large amounts of gastric hypersecretion
- non-β-islet-cell tumors of the pancreas
….. that secretes gastrin, which causes gastric acid hypersecretion, are related to Z-E syndrome
gastrinomas/neuroendocrine tumors
Z-E syndrome usually results in…
PUD
diarrhea
2 causes of PUD
- H. pylori
- NSAID use
Increases HCl production, inflammatory cytokines, tissue necrosis factor-alpha, B-Cell response that consists of IgG and IgA antibodies
H.pylori
Stool samples will have low pH and contain glucose
lactase deficiency
Lactase deficiency differential diagnosis requires …. in conjunction with the lactose tolerance test
oral glucose tolerance test
Disorder that leads to chronic diarrhea when there is…
- ileal disease (Crohn’s disease)
- after resection of the terminal ileum
- cholecystectomy
- IBS
bile salt malabsorption
bile acids
Glycocholic acid and taurocholic acid
Exist as taurine or glycine conjugates (salts)
bile acid function
- Act as surface-active agents to form micelles
- Facilitated digestion of triglycerides
- Absorption of cholesterol and fat-soluble vitamins
Condition in which large amounts of serum proteins pass into the bowel lumen and ultimately into the feces
PLE
hypoalbuminemia
hypoalbuminuria
PLE
PLE associated with…(3)
- Inflammation or ulceration of bowel
- Intestinal lymphatic system is obstructed
- Altered immune status and some food allergies
Characterized by transmural inflammation of the GI tract
Crohn’s disease
likely to overgrow in SI
Escherichia coli and Bacteroides species
- conjugated bile salt deficiency; fat malabsorption
- B12 deficiency
- abdominal pain, diarrhea, and steatorrhea
bacterial overgrowth in SI
Impaired esophageal body peristalsis and incomplete lower esophageal sphincter relaxation
achalasia
Symptomatic delay in gastric emptying of solids or liquid meals secondary to impaired gastric motility
gastroparesis
Diffusely impaired colonic propulsion or by outlet abnormalities
constipation
Result of an inappropriate T-cell-mediated immune response to diet
Celiac’s disease (Gluten)
toxic parts of gluten to Celiac pts
gliadins
hordeins
secalins
Leads to intestinal epithelial damage and release of tissue transglutaminase
celiac
———- cancer (3rd highest for new cases of cancer)
———- cancer (↑ alcohol and tobacco use)
colorectal
esophageal
Rare, but most common GI neuroendocrine tumor
Age range 20-90 years old, peak 50-70 years
carcinoid tumor
- Arise from enterochromaffin cells of the GI tract
- Appear as well-circumscribed, round, submucosal lesions, and the cut surface appears yellow due to lipid content
carcinoid tumor
Cells can be stained with potassium chromate (chromaffin) due to the presence of serotonin in the cell
carcinoid tumor
Classification based on origin: foregut, midgut, hindgut
carcinoid tumor
lab tests for PUD
- Helicobacter pylori biopsy
- serum IgA, IgG
- cytotoxic associated antigen A (CagA)
- NSAID levels
celiac lab tests
- Gliadin antibodies (IgA & IgG)
- IgA-antitissue transglutaminase antibody
- IgA-endomysial antibody
Z-E syndrome lab tests
Basal acid output
gastrin
carcinoid tumor lab test
5-hydroxyindolacetic acid
PLE lab test
Alpha-1-antitrypsin
High Fasting gastrin levels >500 pg/mL (<100)
High Basal gastric acid output >25 mmol/h (2-5 mmol/h)
Z-E syndrome
Urea breath tests use radio-labeled carbon or carbon dioxide
PUD (H. pylori)
POC uses whole-blood to measure IgG antibodies, serum for IgA, IgG, and cytotoxin-associated gene A proteins
PUD (H. pylori)
lactose tolerance test >30 mg/dL above baseline
excludes lactase def.
principle of lactose breath hydrogen test
Hydrogen is not an end product of mammal metabolism, but breath hydrogen is derived from bacterial metabolism in the intestinal tract that is absorbed into the circulation and exhaled in the breath.
lactose breath hydrogen results
Normal breath hydrogen: 10 ppm (uL/L)
Lactose malabsorption: >20 ppm (uL/L)
Less frequent procedure uses 14C-xylose or 14C-glycocholic acid
bacterial overgrowth
Whole-body scan after oral synthetic radioactive selenohomocholyltaurine (SeHCAT)
pos?
bile salt malabsorption
+ if retention of oral dose <10%
Measurement of 7α-hydroxy-4-cholesten-3-one
tandem mass spec
bile salt malabsorption
fecal clearance of α-1-antitrypsin test
pos?
PLE test
PLE patients: Fecal clearance of AAT ↑ and the amount of protein loss ↑
