Exam3Lec8GI:PharyngealEsophagealFxn,Stomach Flashcards
Phagocytosis/Endocytosis of larger particles, digestionm and absoption is done by what organelle?
Lysosomes
The digestive system is set up to have which structures to increase surface area and absorb macromolecules?
Villi and Microvilli
What is the shape of multicellular organisms in the digestive system?
Hollow and have a cavity or lumen for optimal digenstion and absorption. This maximizes surface area for exchange
If the shape is not hollow: Greater Ratio of Volume to Exterior Surface Area than in a Single Cell
What is the fxn of the GI?
Take relatively large, solids or gels, and digest them into smaller molecules that can be absorbed as nutrients, while still serving as a secondary nervous system (ENS) and a barrier to toxins, bacteria, parasites, etc.
have lots of NT and aff and eff signals from gut
Most of your immune system/ cells are where?
In the gut
What acts as a “blender, acid sterilzer, reservoir”?
Stomach
chopper=mouth for mastication
acid in stomach is needed to start proleotic digestion and neutralize pathogens
What acts as a “detergent supplier” in the GI?
Gallbladder
Most absorption in the GI occurs where and what is its anatomy?
Small intestine, hollow tube
What are the phases of digestion?
- Cephalic
- Gastric
- Early intestinal
- Late intestinal
The intensity of the cephalic response in digestion depends on what?
Intensity of response varies with food type (sweet, sour, salty, bitter) to influence our preference, digestion and possibly energy balance
can dictate the amt of food we eat
Explain the cephalic phase of digestion
- Stimuli: auditory (pavlov’s dog), cognitive, visual, olfactory, taste
- Higher brain centers
- Dorsal vagal complex in brainstem
- Incr PNS signaling by activating vagal nerve
- Effector response: saliva,gastric, and pancreatic juice secretion, Mild contraction of the gall blader (sphincter closed)
What is the 2 stage model of saliva secretion?
Primary secretion: ptyalin, mucous, extracellur fluid, Amylase-containing (isotonic, lvs of Na+, K+, Cl-, and HCO3- similar to plasma)
Secondary secretion: modification of ionic contens (absorbs Na+, Cl- and dumps K+ and HCO3- to neutralize activity)
oral microbiomse inflences gut microbiome an d can cause dysbiosis
Fxn of saliva
neutralize acidity
What is the mechanism of Acinar cells in salivary secretion?
- Secretion of K+ and HCO3-
- Also secrete enzymes fats including alpha-amylase, lingual lipase, and kallikrein and mmunoglobulin A (IgA)
kallikrein and mmunoglobulin A (IgA): impt for neutralizing pathogens, sterilizing/barrier fxn
lingula lipase digest fats
What is the role of the salivary ductal cells in salivary secretion?
Ductal cells modify initial saliva to produce final saliva
* Absorb Na+ and Cl- decr concentration in saliva
* Secrete K+ and HCO3- incr concentrations in saliva
* salivary HCO3- neutralize oral bacterial acids
part of secondary secretion
pg 15 table
What does chewing (mastication) do? How does these components play a role?
* Incisors
* Molars
* Saliva
* Chunks of food
increases surface area
* Incisors: 30-80 pounds of pressure
* Molars: 100-160 pounds of pressure
* Saliva: provides lubrication, pre-digestion
* Chunks of food: turns into liquid bolus before food in stomach moves to SI
What are the 5 types of taste qualities in gustation and olfaction?
- Bitter (toxins)
- Salt
- Sweet
- Sour
- Umami (MSG)
umamu=detects glutamate in food (Monosodium glutamate)
What is the swallowing reflex coordinated by?
The medulla oblongata which transmits the contraction of skeletal muscle, sphincter, and smooth muscle groups
What is dysphagia?
Difficulty/discomfort swallowing (MS, ALS, injury)
What are the 3 integrated phases of normal swallowing (deglutition)
- Oral
- Pharyngeal
- Esophageal
Fill in the black boxes for each phse of normal swallowing
Explation the coordination between different structures within the esophagus in order to deliver food to the stomach
- Perilstalsis of bolus to the stomach by UES contraction
- Opening/relaxing of LES to allow food and contents to enter
- Receptive relaxtion in stomach
the coordinated sequence of contracrio and relaxtion in the upper esophageal sphicnter, the esophagus, and the lower esophageal sphicnter is necesarry to deliver food to the stomach
Which nerve coordinates swallowing response?
Glosso pharyngeal + vagal afferents
tongue is under autireg and some conscious regulation
LES is part of which organ?
Diaphragm
site of hiatal hernia
What prevents influx of air into the stomach?
Sphincters and reflux gastric contents into the esophagus
Can we sense acid in the esophgus?
NO, we could have lots of damage to esoph but might not feel it
Explain how the pressure changes as we reach the LES
What are the 3 states of GI sphincter?
Resting state: tone/closed
Relaxation/open
Constriction/Tightly closed
Resting State: Tone/Closed
pressure
fxn
Pressure in Sphincter > Adjacent Segments
Inhibits movement through sphincter
Relaxation/Open
pressure
fxn
Pressure in Sphincter = Adjacent Segments
Allows movements through sphincter
Constriction/Tightly Closed
Pressure
Fxn
Pressure in Sphincter»_space;> Adjacent Segments
Important to prevent flow
What is the fxn of the lower esophagus? (2)
- Swallowing–> triggers Promary peristalsis
- Distention in Esophagus–> triggers secondary peristalsis (backup mechanism)
Distention in the esophagus can initiate can initiate peristalsis through both ____ and ____ reflexes
local and vago-vagal reflexes
What two ligans are the major mediatirs for peristalsis through local and vago-vagal reflexes?
Ach (contraction)
NO (relaxation)
Why do secondary peristaltic waves occur ?
to clear any remnants of the food bolus.
What is Dysphagia?
Difficulty in Swallowing
What can cause Dysphagia?
abnormalities that alter the mechanics of swallowing (e.g. GERD, Achalasia, Cancer)
Can also arise secondary to neurological problems (patients with a stroke or ALS)
What the 3 stimuli stimulates the esophagus? What is their receptor and response?
facilitates esophageal contration
Ingestion of cold substances does what to the esophagus?
Causes inhibition of esophageal peristlasis and can produce pain
ingesting cold slows down neuroactivity
What are common factors that incr and decr pressure?
INCREASE: Increased intra- abdominal pressure and Elevated gastric pH
DECREASE: Fat, Chocolate, Peppermint * Alcohol, Smoking (nicotine), Gastricdistension (aerophagia)
aerophagia: eating too much air
What occurs with esophagitis and what is the therapy used?
decreased resistance of mucosa to acid and pepsin
Tx: GERD therapy
What is GERD therapy?
focuses on control of gastric secretion.
Consists of: Lifestyle modification, medication (PPIs -protein pump inhibitrs can decr gastric acid, overuse can inhibit B12)
If severe: can perfomr fundoplication (fundus wrapped around lower part of esophagus) essentially a sphincter wrapped around a sphincter
What state is the stomach in during swallowing?
hy
Receptive relaxation
hy
What occurs during receptive relaxation?
- Decreased SM tone
- incr stomach compliance
- incr acid secretion
What occurs in the stomach during mixing and grinding?
Jet like retropulsion (contents moves from fundus to body to antrum and can move back to fundus)
liquid content needs to be isotonic
food can move back and forth
What is the fxn the pace maker region located in the the stomach?
Pacemaker region: facilitates contraction through the interstitial cells of cajal (part of myenteric plexus )
What is the myogenic bases of GI phasic contraction?
Slow Waves/Basal Electrical Rhythm
What is slow wave threshold?
The potential which must be reached before a slow wave can be propagated in smooth muscle
How long is BER (freq of contraction) in different segments of the gastro intentinal tract?
Stomach ~ 3/min
Duodenum ~ 11-12/min ( more contraction b/c longer distance to push)
Distal Ileum and Colon ~ 6-7/min (stronger force needed)
Emesis (vomiting) is impt for what?
Neural control
can be activated by pain and sight of someone vomiting
What occurs with emesis?
- Incr salivation (bicarb)
- Retching (somatic muscle actions)
- Suppression of respiration (prevent aspiration)
- BER suspended & replaced with bursts of orally propogating electrical activity.
- Retroperistaltic contractile complex (to propel food backwards-back out)
Fxn of pariteal and chief cells
Parietal: makes HCL and IF, needed to absorb Vit B12
Chief: located in gastric pit; makes pepsinogen proenzyme, is converted to pepsin in presence of acid
For HCL, IF, and Pepsinogen what is the source of these gastric secretory product and the function?
HCL
* source:parietal cell
* fxn: hydrolysis: sterilization of meal
IF
* source: parietal cell
* fxn: viramin B12 absorption
Pepsinogen
source: chief cells
fxn: protein digestion
What the fxn of histamine, gastrin, gastrin releasing peptide,ACh, and Somatostatin?
regulation of grastric secretion
What enzyme is essential for production of H+ ions? (HCl)
carbonic anyhdrase
an inhinbitor of this enzyme inhibits bicarb so there is more neutralization
What occurs in the rapid transition from resting to secreting state in the parietal cell
there is a 5-10x incr in surface area
mediated by: Ach, Histamine, Gastrin
M3, H2, and CCk-B are all activated synergistically
What 3 stimuli work in a synergistic manner leading to potentiation (release of acid)
Histamine
ACh
Gastrin
What does vagal activation stimulate?
Multiple cell responses via neurotransmitter
What does vagal activation stimulate?
Multiple cell responses via neurotransmitter?
Pepsinogen and acid secretion are?
Tightly connected
What does acid in the antrum stimulate?
Somatostatin release to inhibit meal-stimulated gastrin secretion
how we stop acid from dumping into stomach
we have HCL stim D cell in lower part of stomach
What does Vagovagal reflex and endocrine release of gastrin stimulate?
Acid and pepsinogen secretion during the gastric phase
What are 4 pharmaceutocal that can limit stomach acid? Give ex of each
-
Antacids: buffer stomach acid
EX: Tums, Maalox, PeptoBismol -
Block ACh receptor (affects many targest, not practical)
EX: Atropine (not oral, many side effects) -
Histamine Receptor Antagonists
EX: Pepcid, Tagamet, Zantac, Axid -
H+/K-ATPase Inhibitors (PPIs)
EX: Prilosec, Prevacid, Nexium
Explain how acid secretion works before/during/after meal
- In between meals (interdigestive phase) acid secretion is normally low.
- When anticipating a meal (cephalic phase of digestion), acid secretion increases
- Acid secretion increases even more while eating, and tapers off as the meal is emptied from the stomach.
What is the importance of mucus?
bicarb is released to neutralize acidic environment
What is Gastrinoma (Zollinger-Ellison Syndrome)
Lxn?
treatment?
Gastrin-Secreting Tumor
* Unregulated gastrin secretion ➔ ↑ stomach acid
* Can cause duodenal ulcers; enzyme inactivation (lipase)
lxn: extragastric (outside stomach)
TX: surgery, proton-pump inhibitors (to prevent damage from acid)
Summary of Gastric Phase of Digestion, Fill in the boxes
