Gi 2 Flashcards by Michael McMahan

What are the 3 main functions of the stomach?

Temporary storage of ingested material
Production of Chyme (Mechanical digestion and mixing)
*Meter delivery of chyme to duodenum

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The following are functions of the ______:
Temporary storage of ingested material
Production of Chyme (Mechanical digestion and mixing)
*Meter delivery of chyme to duodenumPartially sterilize meal
Initiates protein digestion (Chemical Digestion)
Produce Specialized Secretions
-HCl acid
-Pepsinogen
-Intrinsic factor
-Mucus
-Hormones/Paracrines

Stomach

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What are the 3 structural portions of the stomach?

Fundus, body, and pylorus

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What are the 2 functional portions of the stomach?

Orad and caudad portion

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What structural part of the stomach secretes mucous, pepsinogen, and HCl?

Body

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What are the 4 stages of gastric motility?

Receptive relaxation
Peristalsis (trituration/homogenization)
Emptying (pyloric sphincter)
Migrating Motility Complex (MMC)

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Accommodate the volume of the mealReduce pressure increases preventing gastric reflux and premature gastric emptying

Receptive relaxation

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Chyme production

Trituration: Mix ingested nutrients with gastric secretions, breakdown large particles and increase SA for digestion

Peristalsis (trituration/homogenization)

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≈ 200 kcal/hr released into small intestine

Important not to overload Small Intestine

Emptying (pyloric sphincter)

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Sweep ingested solids that cannot be digested out of stomach and through intestinal tract
Occurs during fastingTakes approximately 90 min to go from stomach to colon

Migrating Motility Complex (MMC)

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_____ is Initiated by:-stretch of gastric or duodenal wall-protein or fat in duodenum (CCK)

Gastric Receptive Relaxation

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______functions: Accommodates increased volume of food and slows emptying.

Gastric Receptive Relaxation

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Generated by pacemaker cells (Interstitial Cells of Cajal) located in GI smooth muscle
Smooth muscle cells undergo spontaneous phases of depolarizations and repolarizations = slow waves or Basic Electrical Rhythm (BER) of stomach
Frequency = 3/minute

Gastric Peristalsis/Trituration

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______ functions:
Acts to mix and break down (triturate) gastric contents (Retropulsion)
Regulate Gastric emptying
Peristaltic wave forces chyme through pyloric sphincter
Causes pyloric sphincter to contract reducing volume released to Small Intestine.

Gastric Peristalsis/Trituration

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What are the 3 things the rate of gastric emptying is influenced by?

Solid vs liquid
Nutrient content
Force of gastric contractions

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On average:50% of stomach contents emptied ___ to ____ hours

2.5 to 3 hours

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Total emptying of the stomach ___ to ____ hours

4 to 5 hours

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Total emptying of the small intestine ____ to ____ hours

3 to 5 hours

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Transit through the colon ___ to ____ hours

8 to 15 hours

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Factors that increase force of antral contractions ______ Gastric emptying

Increase gastric emptying

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What are the 2 things that increase force of antral contractions that increase gastric emptying?

Gastrin and Distension of stomach

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Factors that decrease force of antral contractions _______ Gastric emptying

Decrease gastric emptying

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What is the one thing that decreases force of antral contractions that decrease gastric emptying?

Contents of Duodenum

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_________ = hormones secreted by duodenum in response to nutrients and acid in chyme.

Enterogastrones

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What are the 3 enterogastrones?

1. CCK 2. Secretin 3. GIP

What enterogastrone is secreted in response to fat and protein?

CCK

What enterogastrone is secreted in response to acid?

Secretin

What enterogastrone is secreted in response to carbs?

GIP

Occurs in between meals (fasting state) approximately every 90 minutes Intervals of strong propulsive contractions Sweep stomach and small intestine of indigestible material Intrinsic to ENS and involves hormone Motilin. Continue until meal ingested.

Migrating Motility Complex (MMC)

______ gland: secretes into duct

Exocrine gland

______ gland: secretes into blood

Endocrine gland

______ gland: Exocrine Gland Produce gastric juice Variety of cell types and secretions

Gastric gland

_____ gland: Abundant Mucus-secreting cells Hormones that regulate gastric function

Pyloric Gland (Antral)

______ gland: | Abundant Parietal and Chief cells

Oxyntic Gland (Corpus)

The parietal cell secretes _____ and reabsorbs _____

Secretes HCl and reabsorbs HCO3

Oxyntic cells are activated by what 3 things?

gastrin, histamine, and acetylcholine

Oxyntic cells are inhibited by what thing?

Somatostatin

Oxyntic cells secrete what 2 things?

2L/day of HCl | Intrinsic Factor

Proton pumps are inserted into the ____ membrane of the oxyntic cells

Apical membrane

– combination of factors creates a greater level of acid secretion than just additive

Synergism

Pharmacologically, inhibiting the activity of any one factor (gastrin, Ach, or histamine) _________ acid secretion

greatly reduces

What is the stimulus for neuronal activation of oxyntic glands?

Stretch of gastric wall

What are the 2 neurotransmitters involved in activating oxyntic gland?

ACh | GRP

As the pH drops, what is released to cause less acid production?

Somatostatin

What phase of GI activation involves sight, smell, and sound?

Cephalic phase

What phase of GI activation involves contents in stomach?

Gastric phase

What phase of GI activation involves contents in intestine?

Intestinal phase

What are the 4 stimulants of the cephalic phase of acid secretion?

Sight of food Smell of food Taste of food Thoughts of food

Increased food in stomach leads to ____ somatostatin due to buffering of acid

Decreased somatostatin

____ phase of acid secretion inhibits acid secretion via neural reflex and enterogastrones

Intestinal phase

What 4 things stimulate intestinal phase of acid secretion?

Increased H+ Distension Osmolarity Fats in Duodenum

In ______ period of acid secretion: Acid is secreted at low levels Lack of buffer (no food) causes low pH in stomach (3) Basal secretions stimulated by Histamine and Ach Gastrin low due to low pH in gastric lumen Function: Possibly to sterilize gastric lumen Basal Secretion Rate = 0-11 mEq/hr Stimulated Secretion Rate = 10-63 mEq/hr

Interdigestive Period

______ functions: Facilitates digestion of proteins. Protects against some pathogens. Increases absorption of B12, iron, calcium.

Acid functions

Binds to and inhibits H+ - K+ pump Produces nearly 100% inhibition. May have side effects related to functions of acid.

PPIs

What are the 2 things secreted by parietal cells?

HCl | Intrinsic factor

_____ is an exocrine product that functions in the Activation of Pepsinogen and Sterilization of meal

HCl

_____ is an exocrine product that functions in Vitamin B12 Absorption

Intrinsic factor

What do chief cells secrete?

Pepsionogen

_____ is an exocrine product that functions in protein digestion

Pepsinogen

_____ and _______ are exocrine products that function in gastroprotection

Mucus/HCO3- | Trefoil factors

What doe surface mucous cells secrete?

Mucus/HCO3- | Trefoil factors

___ is made by ECL cells

HIstamine

_____ is made by G cells

Gastrin

_____ is a endocrine product that functions in regulation of gastric secretion

Gastrin

_____ and ____ are neurotransmitters that function in regulation of gastric secretion

GRP | ACh

_____ and ______ are paracrines involved in the regulation of gastric secretion

Somatostatin and histamine

Somatostatin is released by _____ cells

D cells

____ is an endocrine that stimulates hunger

Ghrelin

_____ is made by Gr cells

Ghrelin

_____ controls emptying of the stomach to the small intestine

Pyloric sphincter

_____ is a structural portion of stomach involved in mixing and grinding; secretes mucus, pepsinogen, and gastrin

Antrum

Glycoprotein secreted by oxyntic cells. Exocytosis •Secretion activated by same secretagogues that activate HCl secretion Mechanisms for secretion unknown but different than acid secretion (inhibitors of proton pump do not inhibit intrinsic factor secretion, but does reduce its function) Required for Vitamin B12 absorption Vitamin B12 important in red cell production; deficiency causes “pernicious anemia.”

Intrinsic factor

Intrinsic factor is required for ________ absorption

Vit B12 absorption

Intrinsic factor is secreted by ______

exocytosis

Secretion of intrinsic factor activated by same secretagogues that activate ____ secretion

HCl

Are the mechanisms for secretion of HCl and intrinsic factor the same or different?

Different

Deficiency in _____ causes pernicious anemia

INtrinsic factor

Secretes pepsinogen to initiate digestion of protein. Exocytosis Pepsinogen activated to pepsin by low pH (inactivated by pH > 5) Protein digestion (not significant) Main activation through local and vagal reflexes that release Ach.

Chief cell

At what pH in the stomach is pepsinogen inactivated?

pH 5

Pepsinogen is secreted by ______

exocytosis

Main activation of pepsinogen is through vagal reflexes that release _____

Ach

Produced by endocrine cells located in oxyntic glands Only known appetite stimulant Individuals given Ghrelin eat 30% more than placebo control Stimulates hypothalamic NT Neuropeptide Y May partly account for the anorexia and weight loss seen in some patients following gastric resection

Ghrelin

What are the 2 main effects of ghrelin?

Increase hunger and eating | Decrease metabolism

____ is the only known appetite stiumulant

Ghrelin

Ghrelin stimulates what hypothalamic NT?

Neuropeptide Y

Why Doesn’t the Stomach Digest Itself?

Gastric mucosal barrier

Two hydrophilic layers separated by hydrophobic barrier Mucus is secreted by mucous cells onto surface of epithelium Contains long chains of oligosaccharides that expand and retain water Viscoelastic substance that coats surface of gastric epithelial cells Limit diffusion of acid through the plane of the gel via a mechanism known as viscous fingering Micro-climate with high pH produced by surface cell secretion of HCO3- Mucus secretion stimulated by Prostaglandins (NSAIDS) Trefoil proteins help stabilize barrier

Gastric Mucosal Barrier

Contains long chains of oligosaccharides that expand and retain water Viscoelastic substance that coats surface of gastric epithelial cells Limit diffusion of acid through the plane of the gel via a mechanism known as viscous fingering

Mucous

The mechanism where mucous Limits diffusion of acid through the plane of the gel is called _____

viscous fingering

Mucus secretion stimulated by _______

Prostaglandins (NSAIDS)

_______ help stabilize barrier

Trefoil proteins

What are the 3 common disorders of gastric function?

Ulcers Mucosal destruction Emptying

If there is no ____, there can be no ulcers

No acid

_____ (bacteria) infection destroys the gastric diffusion barrier

Helicobacter pylori

_____ is a g cell tumor that increases gastrin and increases acid

Zollinger-Ellison Syndrome

Disorders of _____ is seen in gastritis, mostly oxyntic gland mucosa where there is decreased mucous leading to ulcers

Mucosal destruction

Disorders of _____ are seen in obstruction, gastroparesis, and dumping

Emptying

Gi 2 Flashcards

(97 cards)