Green - Stomach Flashcards
Distal region of stomach that contracts to mix food and propel it into duodenum
Caudad stomach
Semifluid mass of partially digested food passed from the stomach to small intestine
Chyme
Impaired/delayed gastric emptying
Gastroparesis
Protein produced by the parietal cell that is required for the absorption of vitamin B12
Intrinsic factor
Peristaltic contractions that occur in the stomach every 90 minutes during fasting; mediated by motilin
Migrating myoelectric complex
Proximal region of stomach that receives ingested meal
Orad stomach
Stomach cell that produces acid and intrinsic factor
Parietal cell
What does the parietal cell produce ?
Acid
Intrinsic factor (B12 absorption)
Disorder caused by lack of intrinsic factor, patient has decreased RBC”s due to lack of vitamin B12
Pernicious anemia
Relaxation of the proximal stomach when food enters it
Receptive relaxation
Closure of the pyloric sphincter that forces food back into the stomach
Retropulsion
Receptive relaxation is mediated by _____ which is initiated by distention of the stomach and abolished by vagotomy
Vagovagal reflex
________ causes the distal stomach to increase contractions, which mixes food w/ gastric secretions and reduces size of particles
Presence of food
Peristaltic contractions of the stomach begin in the _______ and proceed distally . As they move distally towards pylorus, both velocity and force of contractions increase
Midstomach
This part of the stomach is responsible for the regulation of intragastric pressure
Fundus
Hunger pangs start _____ hours after last meal and continue for 3-4 days before subsiding
12-24 hours
When does gastric emptying occur ?
When chyme is decomposed into small enough pieces to fit thru pyloric sphincter
(Following normal mixed meal this may take about 3 hours )
What is the order of gastric emptying for protein-rich food
Fat-rich food
Carbohydrate rich food
Carbohydrate rich food leaves faster than protein rich food which leaves faster than fat rich food
(Will feel full longer on fat rich diet)
The rate of gastric emptying is _______ to the pressure in the proximal stomach ?
Inversely proportional
The rate of gastric emptying is controlled Mostly by >
Signals from the duodenum
What are some things that can inhibit gastric emptying ?
High [H+] concentration, high protein or fats, non-isotonic solutions
Increased distention of proximal stomach
Increased pressure of the proximal small intestine
Impaired/delayed emptying
S/s: fullness, loss of appetite, nausea, vomiting
most common cause DM but can be 2ndry to meds that slow contractions in intestine (anticholinergics), neuro disorders
Gastroparesis
Why can increased gastric emptying cause diarrhea?
Because there is an increased osmotic load in the small intestine
What can increased gastric emptying cause?
Diarrhea - increased osmotic load in small intestine
Duodenal ulcers - stomach acids reach the duodenum bc they aren’t equalized in stomach and cause ulcers
Explain dumping syndrome
Lower end of small intestine fills to quickly w/ undigested food from stomach
Common after stomach sx
Early phase (during or right after meal); nausea, vomiting, diarrhea
Late phase (1-3 hours after meal)- sweating, weakness, dizziness
Symptoms are due to too much fluid in intestine and hypoglycemia
What are the two regions of the stomach in regards to secretory function ?
Oxyntic gland mucosa
Pyloric gland mucosa
Functional secretory area of the stomach
Secretes mostly gastrin
Secretes some pepsinogen and mucous
Pyloric gland mucosa
Functional secretory area of the stomach.
Secretes pepsinogen, acid, intrinsic factor, and mucous
Oxyntic gland mucosa
Parietal cells secrete
Acid and intrinsic factor
Chief cells secrete ?
Pepsinogen
Stem cells of the oxyntic gland are located in the mucous neck (some of these also secrete mucous) and can proliferate and differentiate into: (x4)
Mucous cells - mucous
Parietal cells - acid and intrinsic factor
Chief cells - pepsinogen
Endocrine cells - regulatory products
What are the four components of the gastric juice with physiological function ?
HCl
Mucous
Intrinsic factor
Pepsin
Begins digestion of dietary proteins
Converts pepsinogen to pepsin (for further protein degredation)
Kills most bacteria that enter stomach
Secreted from parietal cells
HCl
Activated by gastric acid and itself
Begins digestion of proteins by breaking internal peptide bonds in the proteins
Vagal stimulation causes the greatest increase in secretion
Pepsin
Stored and secreted as pepsinogen
______ stimulation causes the greatest increase in the secretion of pepsinogen
Vagal
Secreted by stomach
Serves as a protective coating for stomach and lubricant and barrier between cells and ingested material
Mucus
Is soluble mucous present in resting stomach?
No
What type of stomach mucous is secreted by mucous neck cells ?
Soluble form
What type of stomach mucous is secreted by surface mucous cells
Insoluble/visible form
Is insoluble mucous secreted in the resting stomach ?
Yes.
In response to chemical or physical irritation
Receptive relaxation is controlled by _______ signaling
Vagovagal
Parietal cells secrete ____ into lumen of stomach and _______ into the bloodstream
HCL
HCO3-
At low basal rates, gastric juice is primarily _____ from nonparietal secretion
NaCl
At high stimulated gastric rates, gastric juice is primarily _______ from parietal secretion
HCl
[K] in gastric juice are always _______ than in plasma
Higher
The blood near the stomach having high pH due to the high activity of the Cl - HCO3- pumps is called
The alkaline tide
During production of. Acid, H+ enters the lumen in exchange for which ion?
K+
Acid secretion initiated by though, sight, taste, or smell of food
Cephalic phase
Region in the fourth ventricle of the brain that initiates vomiting
Chemoreceptor trigger zone
Substance that causes vomiting
Emetic
Acid secretion initiated by entry of food into the stomach
Gastric phase
Acid secretion initiated by the presence of protein digestion products in the duodenum
Intestinal phase
Release of acid by the parietal cell after initiation by multiple stimulants;
The amount is greater than the sum of release by each individual stimulant
Potentiation
What are stimulants of acid secretion?
ACh
Histamine
Gastrin
Ca and cAMP (by increasing concentration of H, K atpases and Cl channels)
How does Acetylcholine (ACh) cause stimulation of acid secretion ?
Acetylcholine binds to muscarinic receptors on the membrane of parietal cells; this activates phospholipase C which catalyzes the formation of IP3 which releases Ca++. Ca++ causes secretion of H+ by. Increasing concentration of H/K atpases and Cl- channels
How do Ca and cAMP cause stimulation of H+ secretion ?
By increased the concentration of H-K atpases and Cl- channels in the apical membrane
How does histamine cause stimulation of H+ secretion ?
Histamine binds to H2 receptors on the parietal cell membrane. H2 then activates adenylate cyclase to form cAMP
How does gastrin cause an increase of H+ secretion in parietal cells?
Gastrin binds to gastrin/CCK-B receptors in the parietal cell membrane. This causes the activation of phospholipase C which then catalyzes the formation of IP3
IP3 then causes the release of Ca++ ions
________ potentiates the actions of gastrin and ACh
Histamine
_______ potentiates the actions of histamine and gastrin
ACh
_______ stimulates the release and synthesis of histamine and the proliferation of enterochromaffin-like cells
Gastrin
______ stimulates the release and synthesis of histamine but not as much as gastrin
ACh
ECL cells has receptors for ____- and _____
Gastrin and acetylcholine
Explain how acid production and stomach pH cycles in relation to meals
At baseline, stomach acidic. You eat food, pH rises, causing release of gastric acid. Food is digested and leaves the stomach. Then pH drops in stomach. When it drops to below 3.0 gastrin release is inhibitted by the release of somatostatin which inhibits acid secretion by parietal cells and gastrin secretion by G cells. Maintaining baseline pH
What are inhibitors of acid secretion ?
Chyme in duodenum
Low pH in stomach
How does chyme in the duodenum affect acid secretion in the stomach ?
Chyme in the duodenum inhibits acid secretion in the stomach by both hormonal and neural methods. There are responses to acidity, osmolarity, and fat content in the chyme that trigger these responses. The responses mechanism is to inhibit gastrin release by G cells and/or acid secretion by the parietal cells
When are the basal rates of acid secretion the highest ?
The evening
What are 2 ways in which the vagus nerve stimulates acid secretion in the cephalic phase of acid secretion ?
ACh directly acts on muscarinic receptors of parietal cells
ACh causes release of GRP
________ is the only major nutrient that stimulates gastric secretion. And works by causing direct chemical release of gastrin from G cells
Proteins (must be broken down to peptides and amino acids)
Caffeine causes a ______ in acid secretion by the stomach
Increase
What are stimulants of acid production in the gastric phase?
Stomach distention
PH increased
Proteins
Caused when protective barrier of stomach breaks down, leading to injury of gastric mucosa by acid and pepsin.
Most commonly in distal stomach
H+ secretion into stomach reduced because some acid leaks into gastric mucosa
Gastric ulcers
3 major causes of peptic ulcers
Infections (helicobacter pylori)
NSAID’s
Alcohol
How does helicobacter pylori contribute to peptic ulcers ?
In stomach, breaks down gastric epithelial barrier
In duodenum, inhibits secretion of somatostatin, allowing increased gastrin release and acid produciton
What are treatments for peptic ulcer disease
Antibiotics
Proton pump inhibitor (blocks H-K-ATPase)
What leads to increased salivation, sweating, rapid breathing, and irregular heartbeat that occurs before and during emesis
General discharge of the autonomic nervous system
The vomiting center is located in the ?
Medulla
What are some afferent stimulations that can cause vomiting (from the vomiting center in the medulla)
Sight/smells
Intense pain
Motion sickness
Tickling back of throat (pulling the trigger)
Distention of the stomach/duodenu
Direct activation of the vomiting center causes what ?
Vomiting w/o nausea or retching
What are 3 places of vomiting control
Medulla (vomiting center)
Chemoreceptor trigger zone (area postrema)
Receptors present in stomach and duodenum
What are the effects of prolonged vomiting ?
Metabolic alkalosis
Hypokalemia (loss of K and decreased reuptake)
Hyponatremia (lost Na in vomit)
Dehydration
