Exam3Lec10GI:ExoPancreas,Liver/Gallbladder,LI Flashcards
Summary review of regulation of pancreatic secretion, fill in blanks
Which peptide enhances insulin secretion?
Oral Glucose-Stimulated Insulinotrophic Peptide
What stimulates GIP release at a larger magnitude? Intravenous glucose or oral glucose
GIP (gastrin inhibitor of peptide) aka K cells
Oral glucose
has less of a glycemic response (b/c releasing more insulin)
Does IV glucose stimulate GIP release?
No bc its not directly in the dudodenum but in BV, it bypasses the GI tract
How much enzymes are produced and secreted by the exocrine pancreas throughout lifee?
Excess, altough production decreases progressively as we age (~30-50 decrease @ ge 75 years)
When do nutrition problems arise?
- If production of pancreatic enzyme falls by as little as 10%
- Outflow of pancreatic juice is obstructed (ex. sphincter of oddi obstructed)
you get malabsoprtion, you arent digesting protein, faits, and carbohydrates
Review: List the sphincters that are present in the Gastrointenstinal Tract
- Upper and lower esophageal sphincters
- Pylorus
- Sphincter of Oddi
- Internal and external anal sphincter
- Illeocecal valve
Know location and function
Which ducts drain to the Duodenum (in duodenal papilla)?
Common bile duct and Pancreatic Duct
What are the 8 major pancreatic enzymes?
- Trypsin , Chymotrypsin, Elastase
- Carboxypeptidase
- Lipase
- Amylase
- Ribonuclease , Deoxyribonuclease
Enzymes: Trypsin, Chymotrypsin, & Elastase, what is the
- Substrate
- Action
- Substrate: Proteins
- Action: Breaks peptide bonds in proteins to form peptide fragments
Enzyme: Carboxypeptide, what is the
- Substrate
- Action
- Substrate: Proteins
- Action: Splits off terminal amino acid from carboxyl end of protein
Enzyme: Lipase, what is the
- Substrate
- Action
- Substrate: Fats
- Action: Splits off two fatty acids from triacylgcerols, forming free fatty acids and monoglycerides
Enzyme: Amylase, what is the
* Substrate
* Action
- Substrate: Polysaccharides
- Splits polysaccharieds into glucose and maltose
Enzyme: Ribonuclease, Deoxyribonuclease, what is the
- Substrate
- Action
- Substrate: Nucleic Acids
- Action: Splits muclei acids into free mononucleotides
The Exocrine Pancreas is a two-stage model utilizing _________ and ________.
Acinar cells; Ductal cells
List the cell types that play a part in pancreatic acinar cell regualtion and explain their functions
- Vasointestinal peptide (VIP) and Secretin
- Both regulate the activation of cAMP
- GRP, ACh, CCK
- All regulate the presence of intracelluar [Ca2+]
Both cAMP & Ca2+ play a role in the phosphorylation of structural and regulatory proteins→Fusion of granules w/ apical membrane and discharge of contents
Exocrine pancreas pancreatic acinar cell is under tight ____ regulation
hormonal
What cell dectects low pH in the duodenum?
HIGH yield
Acid sensing S-cells (aka ductal cells)
What hormone is stimulated pancreatic duct and what does it secrete when S-cells detect low pH?
S-cells: Ductal cells
HIGH yield
Secretin is stimulated and it secretes HCO3- to raise duodenum pH
Overall goal: ↑ pH of environment so that enzymes can fucntion properly
Secretin receptors are ____ expresed on ____
HIGH yield
Densely, Pancreatic Ductular Cells in Humans
What action(s) liberate free fatty acids?
Gastric mixing and triglyceride digestion by gastric lipase enzyme
Gastric lipase ↑ liberation of TAG
What are fatty acids a potent stimulate for?
CCK release
after gastric mixing and trig digestion, you get an emulsion of monoglycerodes and FFA activing CCK release in duod
Which cells in the duodenum releases CCK and how is it activated?
- I-cells
- Free fatty acids(high protein or high carb meal)
What are the roles of CCK?
- Relaxes Stomach
- Can influence eating behavior (satiating effect)
Satiation: Process that causes on to stop eating
How much of TAGs are digested in the stomach?
TAG: Triglycerides
Approx. 10%
Which enzymes are required for the activation of some pancreatic digestive enzymes?
HIGH yield
- Brush Border Entrokinase (aka. Entropeptidase)
- Luminal Tyrsin
trypsin willl turn proenzymes into their enzymatic form
What does CCK stimulate and by which methods?
- Stimulates Gallbladder contraction & Sphincter of Oddi Relaxation
- Neural and Humoral Pathways
The sphincter of Oddi is ____ by the hormone ____ via ____
HIGH yield
The sphincter of Oddi is relaxed by the hormone cholecystokinin (CCK) via vasoactive intestinal peptide (VIP)
CCK stimulates pancreatic enzyme secretion by what pathway(s)?
Neural and hormonal
What materials are entering the large intestine (colon) via what structure?
HIGH yield
- Entry of undigestible/unabsorbed material through the ileocecal sphincter
Unabsorbed material= soluble (ex. pectin)/unsoluble (ex.cellulose) fibers
What the the Colon (LI) a final site for?
HIGH yield
- FInal site for absorption of water and ions (many under hormonal control)
What happens to undigested nutrients (fibers) in the colon?
HIGH yield
Are metabolized by intestinal flora(bacteria) and converted to short chain fatty acids (SCFAs), neurotransmitters (ex. 5HT-3, dopamine) and vitamins (VIT K)
Fiber→colonic bacteria→SCFAs→feed colonocytes
What triggers Peptide YY production and release in the Colon?
YY=tyrosine-tyrosine
Protein and Fat
Also in Ileum before food reaches circulation
Fat in ileum and colon release peptide YY does what?
It inhibits meal-stimulated GI functions
slows dig and transit rate so we can absorb food better
How does the release of PYY inhibit meal stimulated GI fxns?
- ↓ Gastric acid secretion
- ↓ Gastric emptying
- ↓ Pancreatic secretion
- ↓ decreased transit rate
- ↓ Colonic motility
PYY has very strong anti appetite effet
List the parts of the Colon
- Terminal Ileum
- Ileocecal valve
- Cecum
- Ascending colon (site of most colon cancers)
- Transverse colon
- Descending colon (↑ [microbome])
- Sigmoid colon
- Rectum
70% of gut microbiome is in DC
What is the main difference in the right and left colon and why?
Function and Slow Wave Propagation differ to help ↑ H2O and electrolyes reabsorption
What is the function of the right and left colon?
- Right colon: Absorption of water and electrolytes
- Left colon: Formation and storage of feces
note diff direction of right, its compacts food in a way that optimizes H20 and electrolyte absorption
What are the three contraction pattern displayed by the colon?
- Mixing Movements
- Haustral Migration
- Mass Movement
Explain the three contraction patterns
- Mixing Movements
- Haustral Migration
- Mass Movements
- Mixing Movements: Strong contraction of circular muscles to ↑ SA→to help main absorption
- Haustral Migration: Back and forth contraction to ↑ H2O extraction
- Mass Movements: Stimulated by eating, laxatives, exercise by enteric NS to ↑ contraction
What occurs with sympathetic nerve stimulation in the colon?
Sympathetic nerve stimulation decreases spike frequency and inhibits colonic contractions
decr AP that is responsible for muscle contraction
What are Interstital Cells of Cajal (ICC)?
- “Pacemakers” and generate slow waves
- aka: BER; basal electrical rhythm
How is the colonic response to a meal initated?
By signals from the stomach, intestines and brain
Gastrocolonic Reflex: neural and hormonal controlled and contributes to defacation
What role does Aldosterone play in the colon?
HIGH yield
- Promotes expression of transporters required for sodium absorption
- Water follows sodium concentration
absoprtion of H20 and water
sodium intake (diet) alter amt of aldoosterone
List the main functions of SCFAs from gut microbiome (5)
SCFAs= Short Chain Fatty Acids
HIGH yield
- Main fuel for coloncytes
- Tumor supressor effect
- Crosesses Blood Brain Barrier (BBB)
- HDAC activity
- Downregulates VEGF and has other epigentic effects
What enhances the production of SCFAs?
Prebiotics and Probiotics fibers that influence colonic bacteria
What mediates the transport of SCFA in the gut?
HIGH yield
Sodium coupled monocarboxylate transporters (SMCT1)
SCFA is absrorbed into circ by SMCT1 (which is coupled with Na+)
What are the different causes of constipation?
- Usually d/t diet
- Drugs
- Diseases
List the dietary aspects that cause constipation (3)
HIGH yield
- Not enough dietary fiber
- High Calcium + Diary
- Dehydration
List the drugs the cause constipation (2)
- Opiates
- Calcium antacids
can decr gastric motillity
List the diseases that cause constipation (5)
- Irritable Bowel Disease
- Hirchsprung’s Disease: lack of ENS in distal colon
- Physiological Stress
- Hypothyroid
- GI cancers
List the causes of Diarrhea (5)
- Viral, bacterial, or parasitic infection in the colon (most common). Drugs too (Antibiotics, PPIs, Chemo, etc)
- Inflammatory bowel syndrome/Crohn’s disease
- Food intolerances: Wheat and diary products, sugar
- Ischemic bowel disease (older individuals)
- Colon
NOTE: Diarrhea kills more children than malaria, measles, and AIDs combined
List the four types of Diarrhea (4)
HIGH yield
- Secretory diarrhea: e.g. Cholera toxin
- Osmotic diarrhea: maldigestion, hyperosomtic
- Motilty-related diarrhea: vagotomy, neuropathy
- Inflammatory: Brush border damage from infection
What are treatments for Diarrhea?
- Antimotility agents (Immodium=Loperamide)
- Nonspecific agents (Pepto-Bismol=bismuth subsalicylate) buffer and anti-inflammatory effects
Loperamide=opioid receptor agonist that stays in stomach (works locally in the gut)
How do you treat Traveler’s Diarrhea?
CDC recommends antibiotics (3 day regimen) or Pepto Bismol (8 doses over 4 hours)
What is Gastritis (inflammatory) ?
What does it cause?
How do you treat it?
HIGH yield
- Serious diarrhea combined with vomiting and retching over several hours
- The fluid loss from the colon will cause metabolic acidosis
- Treatment: Go to ER for anti-emetic, IV fluids, and anti-diarrheal
Anti-emetic: anti-vomiting
What is Irritable Bowel Disease (IBD)
NOT IBS and Celiac
HIGH yield
- Chronic inflammation of bowel; unknown reasons
- Include Crohn’s Disease and Ulcerative Colitis
List the 4 abnormalities found in IBD
HIGH yield
- Inapproriate immune response to normally innocuous gut flora
- Damage to intestinal: maldigestion/malabsorption; defects in barrier function
- Malabsorption of bile acids in terminal ileum impacts colonic electrolyte transport, leading to diarrhea
List the 6 abnormalities reported in Irritable Bowel Syndrome (IBS)
- ↑ incidence of 3/min slow waves (↑ motility=diarrhea)
- ↓ myoelectric response to feeding (↓ motility=constipation)
- ↑ response to CCK and cholinergic agents (↑ pancreatic secretions)
- ↓ stressed-related small bowel dysmotility (slowed digestion)
- ↓ threshold for pain caused by distension (hypersensitve b/c cytokine & chemokine receptors increase)
- ↑ psychophsiologic scores
you can have incr ir decr in slow waves whichc an cause diahrrea or constipation
nerve pathways in enteric ns are hyperactivates b/c incr cytokine elease making nerve ending more senstitive to distensing pain
