3 Secretions Of The GI Tract And Pancreas Flashcards by Abby Finder

Parotid glands are what type of glands?

Submaxillary/submandibular glands?

Sublingual glands?

Serous

Serous and mucous cells; fluid and mucin glycoprotein

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Structure of salivary glands:

_____ produces initial saliva.

____modifies saliva.

_____ contracts to eject saliva as stimulated by neuron I put

Acinus

Striated duct

Contractile (myoepithelial cells)

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Initial digestion of starches, lipids, and dilution of food, lubrication with mucus for swallowing

Saliva

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Kallikrein secreted in saliva used to make _____.

Bradykinin for vasodilation

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Composition of saliva

Water, electrolytes, alpha amylase (ptyalin), lingual lipase, kallikrein, mucus

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Saliva is ______ compared to plasma.

Higher levels of _____.

Lower levels of _____.

Hypotonic

K, HCO3

Na, Cl

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What cells modify the saliva?

How?

Ductal cells

Saliva was isotonic and plasma like; ductal cells modified the plasma solution to make it hypotonic (saliva)

There is a net absorption of solutes because ductal cells are impermeable to water and not absorbed with the solute->solution becomes hypotonic

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What pumps are on the luminal membrane (apical) of a ductal cell?

Basolateral membrane (blood)?

IN/OUT

Na/H
Cl/HCO3
H/K

K/Na
——/CL
HCO3,Na/——

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Why are there multiple channels moving H and HCO3?

Allow the enzymes to work because they work optimally at different pH levels

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Parasympathetic innervation of salivary glands

Sympathetic innervation

Fx?

Facial and glossopharyngeal N

Originate from T1-T3 and superior cervical ganglion

Increase salivary secretions

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Sympathetic postsynaptic nerve fibers extend to glands by _____.

Periarterial spaces

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Salivary gland parasympathetics stimulated by _____.

Inhibited by ______.

Conditioning, food, nausea, smell

Dehydration, fear, sleep

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Stimuli->parasympathetic response though _____ nerves-> release ______ binding to ______ receptors in the tissue->secrete _____ in the acinar/ductal cell.

CNVII, CNIX (facial and glossopharyngeal)

ACh

Muscarinic

Ca, IP3

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Stimuli->sympathetic response through _____ nerves->release _____ binding to _____ receptors in the tissue -> secrete ______ in the acinar/ductal cell

T1-T3

Beta

cAMP

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Main components of gastric juice and fx

HCl: initiates protein digestion; converts pepsinogen to pepsin; kills bacteria

Pepsinogen: inactive precursor to pepsin

Intrinsic factor: secretes vitamin B12

Mucus: lines the stomach and protects, lubricates, neutralize acids

Water

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Cells and location of the oxyntic gland

In gastric mucosa of proximal stomach, little in body and fundus

Parietal cells
D cells
Mucous cells
ECF cells
Chief cells

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Cells and location of pyloric gland

Distal stomach (antrum)

G cells
D cells
Mucous cells
ECF cells

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Location and fx of parietal cells

Body (oxyntic glands)

Secrete HCl (pepsinogen->pepsin)
Increase secretion of H ions (HCl) so more acidic->increase absorption of HCO3

Intrinsic factor

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Alkaline tide

Venous blood has a higher pH than arterial blood

Because net secretion of HCl and absorption of HCO3 in parietal cells

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Location and fx of G cells

Antrum (pyloric gland)

Secrete gastrin

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Parasympathetic stimulation of G cells by _____ nerve-> release ______-> directly stimulate release of gastrin

Vagus N

GRP

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Parasympathetic stimulation of _____ nerve -> releases ______ binding to muscarinic receptors on D cells -> stimulating D cells to secrete somatostatin-> indirectly _____ gastrin release.

Vagus N

ACh

Inhibits

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Somatostatin is secreted from _____. Act on G cells by _____ gastrin release.

Negative feedback: gastrin ____ somatostatin secretion

H in lumen stimulates _____ secretion.

D cells

Inhibiting

Increases

Somatostatin

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Location and fx of chief cells

What stimulates chief cells?

Body of stomach in oxyntic glands

Secrete pepsinogen

Vagus N

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Pepsinogen needs a ____ pH. Why? inactivated at a _____ pH.

Low Pepsinogen is converted to pepsin (breaks down peptides/proteolytic enzyme) at the optimal pH of 1.8-3.5 (LOW) Therefore needs parietal cells to secrete HCl (H+) and decrease pH High

Vagus N -> releases ACh -> binds to M3 receptors on parietal cells-> stimulate H+ secretion-> triggers _____ reflexes-> stimulates chief cells to secrete _____.

Cholinergic Pepsinogen

Secretion and CCK come from ______ and affect what contents of stomach

Duodenum

Location and fx of gastric mucous cells

Antrum of stomach Mucus and pepsinogen

K/H pump on the _____ membrane of parietal cells. Cl/HCO3 pump on the _____ membrane of parietal cells. Fx? Powered by _____.

Apical/lumen Basolateral/blood How H+ is secreted because Cl follows into lumen HCO3 absorbed into blood ALKALINE TIDE Na/K ATPase pump

K/H pump on parietal cells is inhibited by what? How?

Omeprazole (prilosec, zegerid) Reduces HCl secretion

Inhibitors of ECL Activators of ECL ECL secretes _____ that binds to a _____ receptor.

Prostaglandins and Somatostatin ACh and gastrin Histamine which binds to an H2 receptor -> G protein -> cAMP -> K/H pump -> H+ secretion

Inhibitor of prostaglandin What effect does it cause?

NSAIDS—allow gastric secretions Inhibit prostaglandins therefore preventing the inhibition of H+ secretion from parietal cells

What inhibits the ACh M3 (muscarinic) receptors on parietal cells?

Atropine

Combined response of two stimulants that exceeds their summed response Require a separate receptor for each stimulant

Potentiation

Histamine potentiates ____ and _____. ACh potentiates _______ and ______. Effects of Cimetidine and Atropine??

ACh and gastrin Histamine and gastrin Cimetidine blocks direct action of histamine, therefore blocks potentiated effects of ACh and gastrin Atropine blocks direct action of ACh, therefore blocks potentiated effects of histamine and gastrin

Three phases of gastric HCl secretion

Cephalic, gastric, intestinal

Stimuli of cephalic phase of gastric secretion

Smell, taste, chewing, swallowing, conditioned reflexes

Mechanism of cephalic phase of gastric secretion

Vagus N DIRECTLY stimulates parietal cells by releasing ACh Vagus N INDIRECTLY stimulates G cells to release gastrin Vagus N releases GRP-> activates G cells -> release gastrin-> stimulates parietal cells to secrete HCl

Stimuli of gastric phase of gastric secretion

Distention of stomach, amino acids, small peptides All stimulate gastrin release leading to HCl release from parietal cells

Activates direct and indirect vagus N stimulation of parietal cells

Distention of stomach

Pyloropyloric reflex

Local reflex in the antrum of stomach that stimulates gastrin release—> H+ release from parietal cells

Stimuli of intestinal phase of gastric secretion

Distention of SI, and presence of digested protein

Gastric juice is a mixture of what two secretions?

Non parietal and parietal

______ secrete intrinsic factor which is required for vitamin _____ absorption in the _____. Lack of intrinsic factor will cause what?

Parietal cells B12 Ileum *** Pernicious anemia

Gastric mucosal defense includes ____. Types of cells

Mucous neck cells (mucous) Gastric epithelial cells (HCO3) Protects against HCl and pepsin

Protective factors of gastric mucosa

``` HCO3 Mucus Prostaglandins Blood flow Gastrin Growth factors ```

Damaging factors of gastric mucosa

``` Acid Pepsin NSAID/aspirin H. Pylori Alcohol Bile Stress ```

_____ is used in the diagnosing of gastrin-secreting tumors (gastrinoma). Why?

In gastrinomas, injection of secretion causes a paradoxical increase in gastrin release Normally secretin inhibits gastrin release

Peptic ulcer disease caused by what?

Loss of protective mucosal barrier Excessive secretion of H and pepsin H. Pylori infection and use of NSAIDS

Gastric ulcers caused by _____ bacteria that secretes _____.

H. Pylori Urease: allows the bacteria to colonize Converts urea to NH3 (decrease H+) therefore increase in gastrin Releases cytotoxins that breakdown the mucosal barrier

Duodenal ulcers ____ secretion higher. H. Pylori inhibits _____ from D cells.

H+ secretion Inhibits somatostatin (nothing to control gastrin) Increase gastrin levels

Gastric H. Pylori infection can spread to the _____ and inhibit HCO3 secretion

Duodenum

H+ secretion is the highest Pancreatic tumor secretes LARGE amounts of gastrin Trophic effect on parietal cell (mass increases)

Zollinger-Ellison Syndrome

Effect of trophic parietal cell from Zollinger-Ellison Syndrome Treatment

Excessive delivery of H+ to duodenum Inactivated pancreatic lipases therefore fat in stool (steatorrhea) Treat with cimetidine, omeprazole, surgery

Two main components of pancreatic secretions

Aqueous solution (ISOTONIC) with HCO3, Na, K, and Cl (to neutralize H+ from stomach) Enzymatic secretion of pancreatic amylase and lipase, and pancreatic proteases (to digest CHO, protein, lipids)

What secretes HCO3 from pancreas? What secretes enzymes?

Ductal epithelial cells secrete aqueous solution with HCO3 Acinar cells secrete pancreatic enzymes

Ductal cells of the pancreas cause a net reaction

Secrete HCO3 and absorb H+ in the blood Modify initial isotonic solution

Three phases of pancreatic secretions

Cephalic, gastrin, and intestinal

Pancreas sympathetic innervation (INHIBITORY) includes _____ nerves from _____ and ______ plexuses. Pancreas parasympathetic innervation (STIMULATORY) includes the _____ nerve; preganglionic fibers synapse in _____ and postganglionic fibers synapse on _____.

Postganglionic Celiac and superior mesenteric plexues Vagus ENS Exocrine pancreas

Pancreatic phases: Cephalic is initiated by ______ nerve by _____ and produces _____. Gastric is initiated by ____ nerve by _____ and produces _____. Intestinal phase contains _____ of pancreatic secretions and stimulates _____.

Vagus N Smell, taste, and conditioning Enzymatic secretions Vagus N Distention of the stomach Enzymatic secretions 80% Enzymatic and aqueous secretions

Duodenal i cells secrete ___ and S cells secrete ____ that help regulate pancreatic secretions during the intestinal phase.

CCK and secretin

Regulated Cl channel on the apical surface of ductal cells in pancreas

Cystic fibrosis transmembrane conductance regulator (CFTR)

In a CFTR mutation, the Cl channel does not work -> can’t regulate/secrete HCO3–> build up of H+ Pancreas will fail early in this disease t

Cystic fibrosis

A carbonic anhydrase inhibitor causes what?

Decrease formation of HCO3 therefore decrease secretion of HCO3 secretion into salivary ducts