Physiology Block 3 Week 13 03 GI Secretion 01 Flashcards Preview

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Flashcards in Physiology Block 3 Week 13 03 GI Secretion 01 Deck (27)

Types of Secretions



Types of Glands

Epithelial Glands
-single cell goblet cells

Submucosal Glands
-small intestine crypts of Lieberkuhn

Deep Tubular Glands
-glands in stomach producing acid and pepsinogen

Complex Glands that empty their product into the GI tract
-salivary glands, pancreas, liver


Factors Causing Glandular Secretion

Direct Contact (mucus)

ENS: tactile stimulation, chemical irritation, gut distention

-parasympathetic: increase secretion (MAJORITY)
-sympathetic: causes light increase in secretion


Daily Secretion of Intestinal Juices Volume and pH

Volume: 6700 mL

pH: all alkaline except gastric secretions (very acidic)


Salivary Glands

Proteins Produced
Types of Glands

Proteins produced:
-ptyalin (alpha amylase) that digests starches from serous gland

Types of Glands:
Submandibular--serous and mucus
Sublingual--serous and mucus


Formation and Secretion of Saliva by a submandibular salivary gland

Primary Secretion:
-extracellular fluid:
During maximal salivation there is less time for modifications therefore saliva composition is closer to extracellular fluid
Quicker moves through, the greater amount will have

Saliva produced by acini have:
More: K+ and Bicarb (secretion)
Less: Na+ and Cl- (absorption)

Nervous Regulation of Saliva Production


Nervous Regulation of Saliva Production

Parasympathetic Control from Salvatory Nuclei in brain stem:

--facial nerve innervates submandibular ganglion:
stimulates submandibular gland

--glossopharyngeal nerve innervates the tongue:
taste stimuli: acid
tactile stimuli: smooth objects

--production of kallikrein by salivery glands:
dilates blood vessels

--Sight and smell of appealing food vs disliked foods (appetite center)

--gastric and small intestine input to increase saliva and neutralize irritating substances


Esophageal Secretion

Mucus: to lubricate passage of food and prevent mucosal damage


Gastric Secretion

Mucous Glands: lubricates and protects gastric mucosa against the effects of acid

Oxyntic (gastric) Glands (proximal stomach= fundus and body):

-oxyntic (parietal) cells: acid and intrinsic factor
-chief cells: pepsinogen
-enterochromaffin-like cells (ECL): histamine


Gastric Acid Production

By Parietal Cells

Main driving force for hydrochloric acid secretion by parietal cells is the H+/K+ ATPase

1. H2O in the parietal cell dissociates into H+ and OH-
H+ actively secreted into lumen canaliculus in exchange for K+ (H/K ATPase)

K+ ions transported into the cell by Na+/K+ ATPase pump on basolateral side (ECF side) of the membrane tend to leak into the lumen, but are recycled back into the cell by the H+-K+ ATPase

The basolateral (ECF side) Na+/K+ ATPase creates low intracellular Na+, which contributes to Na+ reabsorption from the lumen

Most K+ and Na+ in cytoplasm, while H+ in lumen canaliculus

2. The pumping of H+ out of the cell permits OH- to accumulate and form biacrb from CO2 catalyzed carbonic anhydrase

Bicarb transpsorted across basolateral membrane into ECF in exchange for Cl-, which enters the cell and secreted thru Cl- channels into the canaliculus

Hydrochloric acid is secreted outward through the open end of the canaliculus into the lumen of the gland

3.Water passes into the canlaliculus by osmosis because of the extra ions secreted into the canaliculus



Secreted by chief cells

Activated to Pepsin by HCl


Intrinsic Factor

Secreted by parietal cells
Necessary for Vitamin B12 absorption in terminal ileum

Acid in stomach causes release of Vitamin B12
R Factor from saliva binds Vitamin B12
R Factor degraded at duodenum by pancreatic bile
Intrinsic Factor from parietal cells in stomach bind Vitamin B12 in duodenum
Vitamin B12-IF complex travel together into the ileum and taken up

**NEED acid prpoduction, IF, functioning pancreas, and normal ileal mucosa

Patients with Chron's Disease do not have normal ileal mucosa--therefore vitamin B12 deficient


Pyloric Glands

Located in stomach antrum

Secretes mucus and GASTRIN

Gastrin produced by G cells in response to presence of proteins
--role in controlling acid secretions

Gastrin inhibited by D cells which produces SOMATOSTATIN in response to low pH


Stimuli for acid secretion

Histamine--H2 receptor = cAMP

Gastrin--CCK-B receptor = Ca2+

Acetylcholine released from vagus and ENS--Muscarinic Receptor = Ca2+


Stimuli for Pepsinogen Secretion

Acetylcholine from PNS or ENS
Gastric Acid

**Acidic environment need to be released


Duodenal Factors Affecting Gastric Secretion

Gastric secretion inhibited by distention, irritation, acidity in duodenum

Fats and Protein Breakdown Products and Altered Osmolality in Duodenum:
Secretin released acting on pancreas and decreases gastric secretion


3 phases of gastric secretion


1500 mL total gastric secretion daily


Gastric Secretion: Cephalic Phase

-sight, smell, thought or taste of food
-originates in cerebral cortex and appetite centers of amygdala and hypothalamus and transmitted to stomach via VAGUS n


Gastric Secretion: Gastric Phase

-vago-vagal reflex (stomach to brain and back to stomach)
-local enteric reflexes
-Gastrin mediated while food is in stomach


Gastric Secretion: Intestinal Phase

-small amounts due to duodenal production of gastrin


Peptic Ulcer Disease

1/3 occur in stomach
2/3 occur in duodenum

Heliobacter pylori***
-cocaine, methamphetamine
-smotional stress
-viral infection
-Crohn's disease

Tx: Proton Pump inhibitor, clarithromycin 500 mg, amoxicillin 1000 mg


Helicobacter Pylori

Has increased risk for peptic ulcer

Lives in antrum, bur can cause effect in duodenum

Flagella and adhesins:
-makes a defect in the mucus layer to travel close to the epithelial surface
-adheres to the surface epithelium

Urease: hydrolyzes urea to NH3 and CO2


Barrett's Esophagus

Risk factor for adenocarcinoma of the esophagus

Proximal or mid-esophageal mass = squamous cell carcinoma
--more related to tobacco use

Distal esophageal mass = adenocarcinoma
--G Junction


Inhibition of Gastric Acid Secretion

Presence of food in the small intestine:

Enterogastric Reflex through Myenteric NS
-activated by acid, protein breakdown products and local irritation

Presence of acid, fat, protein breakdown products, hypoosmotic and hyperosmotic factors, local irritation in upper small intestine results in hormones that inhibit gastric secretion:
-Gastric Inhibitory Peptide, Vasoactive Intestinal Peptide, Somatostatin


True facts regarding salivary glands include all of the following except?

A. The submandibular gland has both serous and mucus components
B. Salivary gland tubules absorb bicarbonate
C. Salivary nuclei are located at the junction of the medulla and pons
D. the pH of saliva is 6-7

B. Salivary gland tubules absorb bicarbonate


Which of the following does not result in increased gastric acid production?

A. Acetylcholine
B. Histamine
C. Gastrin
D. Somastostatin

D. Somastostatin


True statements about peptic ulcer disease includes all of the following except?

A. ulcers are located in the stomach and small intestine
B. ulcers are most commonly due to NSAIDs
C. ulcers are most commonly treated with antibiotics and acid suppression therapy
D. ulcers can lead to gastric outlet obstruction

B. ulcers are most commonly due to NSAIDs

H. pylori