GI Module 2 Flashcards
After initial digestive processes the stomach propels food into the ________.
Duodenum
What is the term for stomach distention that stimulates vagal mechanoreceptors which reflexively stimulates vagal VIP release to relax smooth muscle of stomach wall?
Vaso-vagal reflex
What is the stimulus for gastric emptying?
Parasympathetic activity
Explain the sequence of gastric emptying (2 main steps)
- Retropulsion-contractions push food back towards body of stomach.
- Last wave “forces” pyloric sphincter to open and allow sm. amount of chyme into duodenum
Pylorus opens a ______ amount.
small (1-2cm)
What passes fastest to the duodenum
liquids
What solids pass fastest to duodenum
Proteins empty faster than fats
What is average time to empty 50% of stomach?
50% after 2-3 hours
What is average total time to completely empty stomach?
4-5 hours total emptying
What factors can increase the rate of gastric emptying?
Larger food volume increase rate
What factors decrease rate of gastric emptying?
Hyper/hypotonic fluid-status of fluid concentration
Fatty Foods-take a long time to break down
Acidic food-neutralization takes time
What type of feedback loop are the factors that decrease or increase gastric emptying?
negative
T/F increased blood glucose will increase gastric motility and gastric emptying.
F!!! Increased blood glucose does increase gastric motility but DOES NOT increase gastric emptying.
What are the major secretions of the stomach? (5)
Mucus Acid Pepsinogen Hormones Intrinsic factor
What are the hormones secreted from stomach? (5)
Gastrin Histamine Somatostatin Serotonin Ghrelin
What is the function of mucus in the stomach?
Protects mucosal layer from acid and pepsinogen
What does the mucus contain that works to neutralize the H+?
High levels of bicarbonate
What is the pH of the mucous layer of the stomach?
7.0 (neutral)
What pH is the acid of the stomach?
1.5 (acidic)
What stimulates mucus secretion in the stomach?
Prostaglandins
Nitric Oxide
What can disrupt the mucus barrier in the stomach (and cause ulceration/inflammation).
- Drugs: Aspirin, NSAIDS, ETOH
- Bile salts - regurgitant from SI
- H. pylori
What is the function of acid in the stomach?
Dissolve food
Inactivation of digested bacteria/microorganisms
Convert pepsinogen to pepsin
Where is acid secreted from in the stomach?
Parietal cells
Acid formation/secretions occurs in “exchange” for ______?
Bicarbonate
Increased gastric acid secretion will increase ______ entering plasma?
Bicarbonate
Acid secretion is stimulated by what?
Ach (acetylcholine)-via vagus nerve (parasymp)
Gastrin
Histamine
What would occur if only one of the three mechanisms for acid secretion occurred?
Only a small amount of acid would be produced. All 3 Ach, gastrin, and histamine work synergistically to produce a large amount of acid.
What works to inhibit acid secretion (5)
1 Somatastatin (universal GI inhibitor)
- Prostaglandin E2 (PGE2)
- Gastric Inhibitory Peptide (GIP)
- Secretin
- Glucagon
What are the 3 gastric phases of acid secretion?
- Cephalic
- Gastric
- Intestinal
What stimulates the Cephalic Phase?
ACh CNS stimulation-sight, smell, taste, thought of food.
“The food channel effect”
What are the 3 subcategories of the Gastric Phase?
- Physical stretch
- Protein Digestion-stimulates G cells to release gastrin
- Acid pH value change-pH inhibits somatostatin allowing increase in acid secretion
What occurs during the intestinal phase?
Negative feedback from food entering duodenum inhibits acid secretion in stomach (SI tells the stomach to slow down)
What are 2 pharmaceutical strategies to reduce acid production?
- H2 receptor antagonists
2. PPI (Proton Pump Inhibitors)
What is the MOA of H2 receptor antagonists?
Inhibit histamine signaling in parietal cells.
What is the MOA of PPI?
Inhibit Hydrogen and Potassium ATPase (proton pump) of parietal cells
Ex of H2 receptor antagonistsj
Cemitinide (tagament), ranitidine (Zantac 75), Famotdidine (Pepcid AC) and nizatidine (Axid AR)
EX of PPI’s
Omeprazole (prilosec), lansoprazole (Prevacid), exomeprazole (nexium), rabeprazole (Aceiphex) and pantoprazole (Protonix)
What is the function of pepsin?
Proteolytic enzyme that breaks down proteins in the stomach.
Where is pepsin secreted from?
The chief cells in the stomach
________ is converted to pepsin in a (acid/alkaline) environment?
Pepsinogen, Acidic (pH less than 2)
When and where is pepsin inactivated?
Pepsin is inactivated as chyme passes into alkaline conditions (pH greater than 5.0) of duodenum
What stimulates pepsin secretion?
Parasympathetic (vagus) stimulation
Gastrin
CCK
Secretin
Gastrin stimulates acid production from _______?
Parietal cells
Where is gastrin secret from in the stomach?
G cells in the antrum of stomach
What stimulates the production of gastrin?
Parasympathetic (at) and presence of digestive proteins
What inhibits the production of gastrin?
negative feedback-increased acid in stomach inhibits gastrin release as well as somatastatin
What can disease is caused by gastrin producing tumors which results in excessive acid production?
Zollinger-Ellison Syndrome
Histamine stimulates HCL from _________ attaches to ____ receptors on ______ cells?
Parietal, H2, parietal
Somatastatin is also called the “____________” throughout the GI tract?
Universal inhibitory Function
What does somatostatin inhibit?
Parietal
Chief
ECL cells
Where is somatastatin released from (what cells?) and in what anatomical location?
D cells (delta) in stomach (antrum), and pancreas and intestines
What stimulates the release of somatastatin?
acid
What bacteria’s metabolic by-products inhibit or destroy D cells which leads to inability to regulate acid production (d/t decreased somatostatin) and eventually an ulcer?
H Pylori
What is the major function of serotonin in the gut? What about secondary locations?
Regulates and promotes guy motility. secondary role is in inflammation. There are many receptors in the body that receive serotonin.
Where is the majority of serotonin produced, and what type of cells produce it?
GI tract, and EC (enterochromaffin) cells. (aka S cells)
What is serotonin syndrome?
diarrhea, vomiting, also increases cardio and CNS functions. “ratchets up the volume switch”
What is Ghrelin known as
Hunger hormome
Other than stimulating hunger what does Ghrelin also stimulate?
growth hormone.
T/F Ghrelin is fast acting and stimulates the sensation of fullness?
F. Ghrelin is fast acting but it stimulates the feeling of hunger
When do Ghrelin levels rise?
Just before a meal
What is the primary site of Ghrelin secretion
endocrine cells mostly in the stomach
What are some secondary locations of Ghrelin secretion?
Kidneys, hypothalamus, pituitary, placenta
What stimulates ghrelin production?
glucagon
What inhibits ghrelin production?
leptin, glucose, insulin, and other indicators of feeding
Which factor has a “huge role of B12 absorption”
Intrinsic factor
Where is Intrinsic factor secreted?
Parietal cells of stomach
What is B12 responsible for in the body?
maturation of erythrocytes.
What will deficiency of B12 absorption lead to?
pernicious anemia
The cells of the stomach have rugae (epithelial folds). On the surface of the epithelial folds what cells are found?
Mucus cells
At the base of the rugae (folds) of the stomach are what glands?
Gastric glands
There are 3 regions of gastric glands in the folds of the epithelium of the stomach. What are they?
Body/fundus regions
Cardiac (transitional) region
Pyloric (antrum) region
What cells exist in the body/fundus region of the epithelial folds of the stomach? (5)
- Mucous cells
- Parietal Cells
- Chief Cells
- Enterochromaffin (EC) cells
- Enterochromaffin-like (ECL) cells
What are mucous cells in the stomach responsible for?
Secrete thin, watery mucous to liquefy stomach contents
What are parietal cells in the stomach responsible for?
Secrete acid (HCL) and intrinsic factor
What are the chief cells in the stomach responsible for?
Secrete pepsinogen (promote protein digestion)
What are Enterochromaffin (EC) cells in the stomach responsible for?
Secrete serotonin (increase motility/GI regulatory role)
What are Enterochromaffin-like (ECL) cells in the stomach responsible for?
Secrete histamine (promotes acid secretion)
What cells are present in the Cardiac (transitional) region of the base of the folds of epithelium in the stomach?
Mucous cells
What are the mucous cells in the cardiac region responsible for?
Secrete thin, watery mucus to liquefy stomach contents
What cells are present in the pyloric (antrum) regions of the base of the folds of the epithelium in the stomach?
Mucous cells
G Cells
D Cells
What are the Mucous cells in the pyloric (antrum) region responsible for?
Secrete thin, watery mucus to liquefy stomach contents
What are the G cells in the pyloric (antrum) region responsible for?
Secrete gastrin (promotes acid secretion/motility and gastric mucosa growth)
What are the D cells in the pyloric (antrum) region responsible for?
Secrete somatastatin-inhibitory to parietal, and chief cells.
What are the surgical options for weight loss procedures?
LAP Band
VBG-stomach stapling with lap band
Gastric Bypass-
Of all the weight loss procedures which has been suggested to be superior in terms of post-op compliance?
Gastric bypass procedures
What are the complications of gastric bypass procedures?
Nutritional deficiencies
dumping syndrome
dorect complications of GI tract
What does the term ‘gastritis’ typically refer to?
Inflammation of the gastric mucosa (lining of the stomach)
What are some causes of acute gastritis?
Drugs, chemicals (NSAIDS
H pylori infection
alcohol and smoking
How long can it take for healing to start with acute gastritis once it is identified?
Within a few days of removing offender (ASAP)
What is the most common type of chronic gastritis?
Type B Chronic Antral Gastritis (4x’s)
What is the assumed to be the cause of type A chronic fundal gastritis?
Autoimmune d/o
What group of people is chronic gastritis most common in?
More common in elderly (degenerative)
t/f Chronic Antral Gastritis is d/t autoimmune dsfn.
FALSE!
What is more common gastric ulcers or duodenal ulcer?
Duodenal ulcer
What is the most common location for gastric ulcer to occur?
antrum
What type of ulcer is more likely to be associated with a higher risk of cancer?
Gastric ulcers
What are the two major r/f for developing gastric ulcers?
Chronic NSAID, aspirin use
H. pylori infection
