GI Phys: Pharangeal & Gastric Phase Flashcards
What are the three saliva glands? Which of these also secrete mucous?
- sublingual glands (secrete mucous)
- Submandibular glands (secrete mucous)
- Parotid gland
What binds B12 in the saliva to protect it from digestion?
-Haptacorrin (R protein)
What is the acinus of the salivary gland?
-The area where fluid is filtered from the blood stream into the saliva duct
How do ductal cells of the salivary glands modify the composition of the saliva?
- Reuptake Sddium and cloride
- secrete protons, Bicarb, and potassium
What does the osmolarity and ionic composition of saliva depend on? Why?
- The rate of saliva secretion
- if secretion rates are high, saliva composition approaches that of plasma because the ductal cells had little time to modify the isotonic saliva made by acinar cells
What does lactoferrin in the saliva do?
- antibiotic property
- binds Fe
What does Muramidase do?
- antibiotic
- cleavage of muramic acid of Gram (+) bacteria
What are the proteins which are contained in saliva?
- Mucin
- a-Amylase
- Lingual Lipase
- Muramidase
- Lactoferrin
- IgA antibodies
- Haptacorrin
-Growth Factors
What is the difference in composition of saliva when stimulated by the sympathetic NS vs the parasympathetic NS?
- Sympathetic: Protein-rich secretions that facilitate respiration
- parasympathetic: more fluid secretion to facilitate digestion
What happens during the oral phase?
- masticated food is rolled as bolus towards the pharynx by the tongue
- contact of the bolus with the pharynx activates the swallowing reflex while inhibiting the gag reflex
What happens during the pharyngeal phase?
- contact of the tongue with the roof of the mouth elevates the soft palate to seal the nasopharynx
- the epiglottis seals the laryngeal opening
- breathing is inhibited
- upper esophageal sphincter is relaxed and the bolus is pushed into the esophagus
What happens during the esophageal phase?
- contraction of constrictos is regulated by the nucleus ambiguous
- food is propelled into the stomach via peristalsis
- relaxation of the lower esophageal sphincter allows food to enter stomach
What is the function of Haptacorrin
(also known as the R protein)?
A. Bind iron and act as an antibacterial agent
B. Bind and protect folate
C. Act as growth factor to intestinal mucosa
D. Bind and protect vitamin B12
D. bind and protect viatmin B12
What is the function of Lactoferrin found in saliva?
A. Bind iron and act as an antibacterial agent
B. Bind and protect folate
C. Act as growth factor to intestinal mucosa
D. Bind and protect vitamin B12
A. Bind iron and act as an antibacterial agent
What mediates secondary peristalsis?
- initiated by stretch, acid reflux, and osmoreceptors
- mediated by local reflexes
What is Achalasia? What are the treatment opions?
- lower esophageal sphincter cannot relax to allow passage of bolus
- due to absence of NO neurons
-treatment includes sublingual nifedipine, BoTox, and surgical myotomy (best outcomes)
A commonly prescribed medication and carried while
travelling is Loperamide (Imodium); it is a modified morphine.
Loperamide is likely to cause:
A. Constipation by increasing the GI motility
B. Diarrhea by decreasing GI motility
C. Constipation by decreasing the GI motility
D. Diarrhea by increasing GI motility
C. constipation by decreasing GI motility
Receptive relaxation in the fundus region of stomach is mediated by which of the following neurotransmitter(s)? A. Substance P B. Acetylcholine C. Dopamine, Nitric Oxide D. Histamine E. Endothelin
C. Dopamine & Nitric Oxide
What factors increase transit time in the stomach?
- Fat
- Protein
- Acid
- Solids
- More food
- pregnancy (progesterone)
- Supine posture (bed ridden)
What factors decrease transit time in the stomach?
- Liquids
- Carbohydrates
- Erect posture
Why does increasing acid content decrease the emptying time of the stomach?
-the acid has to be neutralized by pancreatic juices, duodenal juices, and intestinal secretion after it is emptied
GERD (Gastro-Esophageal Reflux Disease) is partly
due to slow emptying of stomach contents.
of the following, which is LEAST likely to cause GERD?
A. Diabetic neuropathy
B. Diet rich in carbohydrates
C. Pregnancy / Progesterone
D. Obesity
E. High fat diet
F. Chronic Alcoholism
G. High protein diet
B. Diet rich in Carbs
Your patient cannot keep food down and is losing weight.
A barium swallow test shows an enlarged esophagus and
a narrowing to a “bird’s beak” at the lower esophageal
sphincter. Manometry shows abnormal or absent peristalsis
in lower body of the esophagus.
Your presumptive diagnosis is:
A. Gastroparesis
B. Stroke in the brainstem resulting in impairment
of swallowing centers
C. Achalasia
D. Gastroesophageal reflux
E. Stomach / duodenal ulcer
C. Achalasia
Why pregnant women are more likely to throw up?
-Progesterone increases the transit time of food in the stomach, making emesis more likely
Why is saliva secreted under low flow rates very hypotonic?
-The ductal cells have had more time to remove ions from the saliva
Where are cells that secrete gastrin and somatostatin located in the stomach?
- the pyloric antrum region
- for reddy, the distal half of the stomach
What causes Zollinger-Ellison Syndrome?
-an abnormal increase in gastrin production
Parietal cells secrete what?
A. Gastrin B. Pepsinogen C. Pepsinogen and lipase D. Somatostatin E. Acid and Intrinsic factor
E. Acid and Intrinsic Factor
How do NSAIDs inhibit mucus synthesis?
- They inhibit COX enzyme that is required for prostaglandin synthesis
- Prostaglandins normally increase mucous production and inhibit acid secretion
Describe Gastrin’s Effects on the CCK receptors. What is the end result?
- Gastrin activates CCK-2 and blocks CCK-1
- when gastrin binds CCK-2 there is an increase in acid secretion
How is HCl secreted by Gastric parietal cells?
- First CO2 dissociates into proton and bicarb
- proton is secreted into lumen via K/H-ATPase
- Bicarb is secreted into blood via HCO3/Cl antiporter
- Cl from cell diffuses into lumen via Cl channel
Describe and contrast the pH of the blood draining from the stomach and duodenum.
- pH of stomach veinous drainage is basic due to acid excretion
- pH of duodenum is acidic due to acid neutralization
- overall effect is pH’s cancel out
What receptor does ACh bind to in the stomach? What is its effect?
- M3 receptor
- Effect is an increase in H+ secretion
What receptor does Histamine bind to in the stomach? What is its effect?
- H2 receptor
- effect is an increase in H+ Secretion
What two things normally decrease acid secretion? What G protein do they work through?
- Somatostatin and prostaglandins
- Gi
Which of the following decreases acid secretion?
A. Alcohol B. NSAIDs C. Gastrin D. Histamine E. Somatostatin F. Acetylcholine G. Misoprostol (synthetic prostaglandin)
E. Somatostatin
AND
G. Misoprostol
What are the 3 functions of gastric acid?
- denature proteins so that pepsin has easy access
- activate digestive enzymes
- kill bacteria
Describe the cephalic phase of gastric acid secretion.
- Stimulated by sight, smell, taste, chewing, swallowing, and hypoglycemia
- These sensory afferents stimulate the vagus to stimulate gastrin release and thus acid secretion
- responsible for 30% of total acid secretion
What percentage of acid secretion occurs during the cephalic phase?
-30%
Describe the gastric phase of gastric acid secretion.
- Distention of the stomach leads to local ENS reflexes and the vagovagal reflex to release acetylcholine and stimulate gastrin production, respectively
- this accounts for 50-60% of acid secretion
What percentage of acid secretion occurs during the gastric phase?
-50-60%
Describe the intestinal phase of gastric acid secretion.
- Protein digestion products stimulate intestinal endocrine cells and intestinal G cells to activate parietal cells to secrete more acid
- absorbed amino acids also directly stimulate parietal cells to secrete protons
- responsible for 5-10% of acid secretion
What percentage of acid secretion occurs during the intestinal phase?
-5-10%
How does H. pylori cause stomach ulcers?
- they break down urea to form ammonia
- this neutralizes the HCl, allowing the bacteria to colonize the antral region
- secretes factors to attract immune cells to induce inflammation leading to damaged mucosa and vasculature, leaking fluid and blood forming an ulcer
Treatment for pernicious anemia is:
- Take multivitamin tablets
- Supplement intrinsic factor
- Take Vitamin B12 tablets
- Take Vitamin B12 intramuscularly
- Supplement Hapracorrin (R factor)
- Take vitamin B12 intramuscularly
Supplementing intrinsic factor is too expensive
What is pernicious anemia?
- a megaloblastic anemia caused by vitamin B12 deficiency
- no intrinsic factor is produced, so eaten vitamin B12 cannot be absorbed
- must be treated with intramucular B12 injections
What do chief cells do in infants?
-the make reNNin, which can digest milk proteins
What do D cells secrete in the GI tract?
-somatostatin
What do ECL cells secrete in the GI tract?
-Histamine
What do G Cells secrete in the GI tract?
-Gastrin
What do I Cells secrete in the GI tract?
-CCK
What do M Cells secrete in the GI tract?
-Mucus
What do S Cells secrete in the GI tract?
-Secretin
What are some things that promote vomiting?
- Dopamine
- Serotonin
- Ach
- Substance P
- Histamine
What are some antiemetics and their targets?
- Scopalamine (Ach receptor)
- Compazine (D2 dopamine receptor)
- Phenergan (H1 histamine receptor)
- Steroids (Transcription)
What does a patient lose if they have profuse vomiting? Describe their plasma status after vomiting.
- fluid, protons, Chloride, potassium
- Plasma status is hypovolemic, alkalemic, hypochloremic, and Hypokalemic
Prolonged and profuse vomiting will result in
which of the following?
A. Hypokalemic, hypochloremic, metabolic alkalosis
B. Hypokalemic, hypochloremic, metabolic acidosis
C. Hyperkalemic, hyperchloremic, metabolic alkalosis
D. Hyperkalemic, hypochloremic, metabolic acidosis
E. None of the above
A. Hypokalemic, Hypochloremic, metabolic Alkalosis
Which one of the following will promote emesis?
A. Muscarinic blocker; B. Histamine blocker; C. Serotonin; D. Dopamine blocker
C. Serotonin
