Gastric, Intestinal, and Pancreatic Function Flashcards
Three functions of the stomach
- Movement of food to the duodenum
- Secretion of digestive enzymes, intrinsic factor, and HCl
- Partial digestion of proteins
Anatomical location of the stomach by naming the three distinct zons
- Fundus
- Body
- Antrum
Specific cell type of the fundus
- Surface epithelial cells
- Mucus cells
Specific cell type of the body
- Surface epithelial cells
- Mucus cells
- Parietal cells
Specific cell type of the antrum
- Mucus cells,
- G-cells
- Chief cells
Specific secretion(s) of surface epithelial cells
To produce mucus and shed and proliferate rapidly (every 3 days)
Specific secretion(s) of mucus cells
Secrete mucus
Specific secretion(s) of parietal cells
- HCl
- Intrinsic factor
Specific secretion(s) of chief cells
Pepsin → pepsinogen
Specific secretion(s) of G-cells
Gastrin stimulates the parietal cells to produce HCl
Five functions of gastric HCl
- Converts pepsinogen → pepsin
- Activates rennin (milk curdling enzyme)
- Combines w/ food proteins to form acid metaproteins which are more easily digested by pepsin
- Prevent bacterial multiplication in the stomach
- Prevents precipitation of ingested Ca2+ so that soluble Ca2+ may be absorbed
Four stimuli for gastrin release
- When proteins, amino acids, and Ca2+ enter the stomach
- Vagus nerve is activated and releases acetylcholine
- Antrum is distended
Three phases of gastric secretion
- Cephalic phases
- Gastric phase
- Intestinal phase
Cephalic phase
- Stimuli and specific secretion(s) produced
Vagus nerve, stimulated by site and smell, stimulates parietal cells to produce HCl and G-cells to produce gastrin
Gastric phase
- Stimuli and specific secretion(s) produced
- In the stomach, gastrin release stimulates parietal cells to produce more HCl
- Local antral distension stimulates further production of gastrin and therefore HCl
- Chief cells respond to acidic environment, pepsinogen is produced that is rapidly converted to pepsin at pH 3
- Chyme is produced (mucus-containing solution)
Intestinal phase
- Stimuli and specific secretion(s) produced
- Ingested food helps neutralize HCl
- Secretion is released, inhibiting gastrin-stimulated acid production and gastric motility
- Gastric secretions cease
Three functions of gastric fluid
- Initiation of protein digestion
- Physical and chemical preparation of ingested food for absorption
- Secretion of intrinsic factor to promote vitamin B12 absorption in the ileum
Four normal constituents of gastric secretions
- HCl
- Enzymes (pepsin (most important), salivary amylase, gastric lipase)
- Mucus
- Intrinsic factor
Three abnormal constituents of gastric fluid
- Blood
- Food
- Organic acids
Appearance of fresh blood in the stomach
Red
Appearance of blood that has remained in the stomach for a period of time
Old blood is converted to hematin by the acidic pH and has a “coffee grounds” appearance
Four indications for gastric analysis
- Aid in evaluation of patients w/ recurrent ulcer disease
- Aid in diagnosis of Zollinger-Ellison syndrome by demonstrating a hypersecretory state
- Determine if patient is able to secrete HCl at all (pernicious anemia)
- Determine the completeness of vagotomy after gastric surgery
Basal Acid Output (BAO)
- Specific diagnostic use for gastric function assessment
No stimulation after you fast and you measure if outputting acid → determine baseline pH
Maximum Acid Output (MAO)- Specific diagnostic use for gastric function assessment
Important in determining if the patient has low acidity or anacidity
Serum gastrin
- Specific diagnostic use for gastric function assessment
Useful in diagnosis of the Zollinger-Ellison syndrome
Schilling test
- Specific diagnostic use for gastric function assessment
Useful in the diagnose of pernicious anemia
Hollander test
- Specific diagnostic use for gastric function assessment
Useful in determining the completeness of vagotomy in peptic ulcer treatment (should not be ↑ in vagotomy)
Recognize five lab findings in stomach cancer
- Achlorhydria in gastric fluid
- Anacidity or hypoacidity of gastric fluid
- Blood (“coffee grounds” appearance) in gastric fluid
- Iron deficiency anemia due to blood loss
Recognize causes for gastric and peptic ulcers
- Helicobacter pylori
- Smoking
- Caffeine
- Alcohol
- Stress
- Physical stress
- Acid and pepsin
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
List the specific cause for the Zollinger-Ellison Syndrome
Gastrinoma
- Gastrin-secreting tumor of malignant cells in the duodenum or from a tumor in a non-beta islet cells of pancreas)
Four typical lab findings for Zollinger-Ellison Syndrome
- BAO > 10mEq/hour
- MAO usually < 25% higher than BAO (i.e., both are high all the time)
- ↑ volume of secretion (160-800 mL/hour)
- Serum gastrin levels 2-20,000x normal!!!
Cause of pernicious anemia
Gastric problems are caused by malfunctioning parietal cells, responsible for HCl production and secretion of intrinsic factor (IF)
Six typical lab findings I pernicious anemia
- Anacidity
- ↓ gastric secretion volume
- Gastric atrophy
- ↑ serum gastrin (>200 pg/mL)
- Macro-ovalocytes
- Hypersegmented neutrophils
Function of the duodenum
- Has 6 major hormones to aid in digestion and protection of the intestinal lining
- Intraluminal hydrolysis of starch, proteins, and lipids
Function of the ileum
- Absorption of vitamin B12 and whatever products of digestion that were not absorbed by the duodenum
- Diffuse neuroendocrine system cells secrete gastrin, secretion, and cholecystokinin into the bloodstream
Function of the large intestine
- Absorption of water from the remaining indigestible food matters
- Absorption of vitamins that are created by bacteria inhabiting the colon
- Fecal compaction until it can be eliminated
Cholecystokinin-pancreozymin (CCK-PZ)
- Source
Secreted by I cells of duodenum when digested proteins/fats enter duodenum
Cholecystokinin-pancreozymin (CCK-PZ)
- Stimulus
Secreted by I cells when protein and fats enter the duodenum
Cholecystokinin-pancreozymin (CCK-PZ)
- Three physiological effects
- Pancreas to produce enzymes
- Gall bladder to contract and empty contents
- Sphincter of Oddi to relax to allow gall bladder and pancreatic contents to enter duodenum
Secretin
- Source
S cells both the duodenum and jejunum
Secretin
- Stimulus
Released when acidified contents of stomach reach duodenum (pH < 5)
Secretin
- Two physiological effects
- Acts in synergy w/ CCK for release of pancreatic enzymes
- Stimulates secretion of large amt of diluent pancreatic fluid rich in sodium bicarbonate
Gastric inhibitory peptide
- Physiological effects
Stimulates insulin release and is responsible for rapid metabolism of an oral glucose load
Vasoactive intestinal polypeptide
- Physiological effects
Causes relaxation of gut circular smooth muscle as well as smooth muscle in blood vessels, causing vasodilation
- Also stimulates pancreatic secretion
Motilin
- Physiological effects
Stimulates the contraction of the smooth muscles of the GI tract and contracts the lower esophageal sphincter
Somatostatin
- Physiological effects
- Most potent inhibitor of endocrine secretions
- Inhibits release of GI and pancreatic hormones, as well as the release of GH and TSH
- Inhibits actions of all these hormones on their target tissues
Compare Crohn’s disease w/ ulcerative colitis
Both: - Form of inflammatory bowel disease - Autoimmune etiology - Genetic Crohn's - Can affect any portion of the intestine - 10-30% test positive for ANCA test Colitis - Disease of large intestine ONLY - 60-80% test positive for ANCA test
Celiac disease
- Cause
Hypersensitivity to grains (gluten)
- Genetics
- Immune system
- Environment
Celiac disease
- Symptoms
- Abdominal bloating and pain
- Chronic constipation and/or diarrhea
- Weight loss
- Pale, foul-smelling stool
- Flatulence
(many more, see slide 108)
Celiac disease
- Treatment
Remove gluten from diet
Best screening test for colon cancer
Occult blood test
Carcinoid syndrome
- Symptoms
Tumors produce serotonin which cause the symtpoms of:
- Hypertension
- Flushing
- Wheezing
- Diarrhea
- Right-sided valvular disease
Carcinoid syndrome
- Lab diagnosis
Screen for 5-HIAA in urine
Carcinoid syndrome
- Treatment
Surgical excision of the tumor(s) is the only treatment
Endocrine functions of the pancreas
- Beta cells secrete insulin
- Alpha cells secrete glucagon
- Delta cells secrete gastrin and somatostatin
Exocrine functions of the pancreas
80% of mass is made of acinar cells, grape-like cluster that produce digestive enzymes
Insulin
- Physiological effects
Uptake of glucose
Glucagon
- Physiological effects
Release of glucose from glycogen
Gastrin
- Physiological effects
HCl production
Consequences of secretin and CCK-PZ release on the pancreas
Secretin:
- Made when acidic stomach contents reach duodenum
- Responsible for bicarbonate release
- Gastrin production in the stomach
CCK-PZ
- Made by intestinal cells
- Responsible for enzyme release from pancreatic acnar cells
Consequences of Vagus nerve stimulation on the pancreas
Can cause pancreatic fluid secretion during cephalic phase of digestion
Five enzymes produced by the pancreas and their substrates
- Amylase
- Lipase
- Chymotrypsin
- Trypsin
- Elastase
Substrate of amylase
Acts on starch and CHOs
Substrate of lipase
Acts on triglycerides
Substrate of chymotrypsin
Cleaves peptide bonds following phenylalanine, tryptophan, and tyrosine residues
Substrate of trypsin
Acts on proteins by catalyzing the hydrolysis of peptide bonds
Substrate of elastase
Acts on elastin
Cystic Fibrosis
- Cause
- Autosomal recessive
- Most common genetic mutation is delta-F508 on the long arm of c’some 7
Cystic Fibrosis
- Symptoms
Disrupts the function of several organs by clogging tubes?
Cystic Fibrosis
- Clinical course
Meconium ileus at birth (bowel obstruction)
- Chronic respiratory infections
- Malabsorption w/ failure to thrive
- Median survival: 30 years
Cystic fibrosis
- Lab findings
Sweat chloride measurement >60 mEq/L on two occasions
Cancer at the head of the pancreas
- Typical symptoms and lab findings
- Detected earlier than other pancreatic cancers
- Jaundice, weight loss, anorexia, nausea
Cancer of beta cell tumors
- Typical symptoms and lab findings
Causes very low blood sugars and associated symptoms
Cancer of alpha cell tumors
- Typical symtpoms and lab findings
- Have a very poor prognosis
- Detected later b/c of lots of diseases that could cause hyperglycemia
Acute pancreatitis
- Common causes
- Cholelithiasis (gallstones)
- Excess alcohol intake
- Trauma, mumps, thrombosis, drugs
- Idiopathic
Acute pancreatitis
- Common symptoms
Acute abdominal pain radiating to the upper back
Acute pancreatitis
- Length of time that amylase and lipase remain elevated in the serum after an attack
- Amylase rises w/in 24 hours → returns to normal in 3-4 days
- Lipase rises about the same time → stays elevated for 2 weeks
Most common cause of chronic pancreatitis
Alcoholism
Two indirect tests used to diagnose chronic pancreatitis
Measure fecal chymotrypsin and fecal elastase-1
Specific diagnostic usefulness of the measurement of elastase-1
- Secreted in any inflammatory state
- Sensitive and specific marker of chronic pancreatitis
Specific diagnostic usefulness of the measurement of trypsin
- Highly sensitive indicator of pancreatic disease
- Recommended as a screening test for cystic fibrosis in 5- day old infants
Which conditions may lead to malabsorption?
- Pancreatic insufficiency
- Celiac disease
- Resection of ilium
- Parasitic infection of the gut (see slide 159)
Why do patients w/ malabsorption syndrome have steatorrhea, weight loss, vitamin deficiencies, anemia, edema, coagulation disorders, and osteomalacia?
Deficiencies of fat and water-soluble vitamins
Four tests used to evaluate malabsorption syndrome
- Carotene
- Microscopic examination of stool for fat
- D-xylose absorption test
- Breath hydrogen test
D-xylose absorption test
- Principle and specific area of the GI tract that is assessed
Assesses the functional integrity of the small intestine
Breath hydrogen test
- Specific diagnostic usefulness
Assesses whether malabsorption is caused by bacterial overgrowth or a lactase deficiency
Describe the multiple endocrine neoplasia (MEN) syndrome
Occurrence of tumors involving two or more endocrine glands w/in a single patient
- Two types → MEN-1 (Wermer’s syndrome); MEN-2 (Sipple’s syndrome)
