Oral Gastric Biochemistry Flashcards by Meghan May

Purpose of saliva

 Provides lubrication that aids in swallowing
 Aids in the digestion of food and enzymatic cleavage
 Produces growth factors for epithelial cells
 Neutralizes bacterial acids
 Mediates taste sensations
 Provides defense against bacterial pathogens

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Neve for parotic

Glossopharyngeal XI

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nerve for sublingual/submandibular

Facial VII

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Primary secreation from saliva

pytalin, alpha amylase, mucus, extracellular fluid

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In saliva, what is abosorbed?

Na+ actively

Cl- passively

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In saliva what is secreated?

K+ activly

HCO3- passively

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Role of Lysozyme (part of saliva)

 Kills gram positive but not gram
negative bacteria
 Cleaves beta 1-4 linkages between NAM and NAG in GRAM POSTIVE bacterial
Cleave beta 1-4 links in in chitodextrins (fungus)

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Enzyme that kills bacterial by producing reactive bromide and iodine molecules

Peroxidase

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Protein that binds iron and prevents bacterial and some fungal growth

Lactoferrin

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Secretory immunoglobulins that upon recognition and binding to bacteria induce
immune reactions

 IgA

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Antimicrobial polypeptides that form pore complexes on microbial cell membranes

 Defensins

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Large highly glycosylated proteins that modulate adhesion of bacteria to oral tissues
including teeth

 Mucins

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Saliva contains Mucin which functions in:

 Lubricants
 Antimicrobial
 Found throughout the GI tract
 Highly O-glycosylated specific glycoproteins

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Whats important about high HCO3- in saliva?

High HCO3 Neutralizes bacterial produced acids

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Is there a lot of Na or Cl- in saliva?

nope

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Shit that can carry viruses in saliva

 Human Herpes
 Herpes Simplex
 Epstein Barr
 Mumps
 Rabies
 HIV

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Xerostomia is caused by what two pathologies

 Cystic fibrosis
–Mutant chloride transporters to plasma
 Sjögren’s syndrome
–Autoantibodies to salivary gland proteins

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What happens in cephalic phase of gastric secreation?

occurs from vagaus–> Ach–> causes secraetion of pepsin (chief) and acid (parietal)

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What occurs in teh Gastric Phase

Local nervous secreatory reflexes
vagal reflexes
Gastrin-histamine stimulation

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What happens during the intestinal phase?

Nervous and hormonal mechanisms

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The VAgus nerve stimulates the relesase of what two things?

Acetycholine and Gastric relesase peptide

What does Ach cause stimulation of?

inhibition of?

Ach stimulates: Parital cells–> HCl and ECL cell –> histamine
Ach inhibits: D Cell–> somatostatin

Gastric releasing peptide stimulates secreation of waht?

G cell (antrum) to release Gastrin

What stimulates D cells to release Somatostatin?

HCl

What inhibits D cells from releasing SST

Acetycholine

Somatostatin inhibits secreation of what three things?

Gcell--> gastrin ECL--> histamine Parietal cell--> HCl

What stimulates G cells to release gastrin? | What inhibits it

GPR | inhibited by SST

Gastrin stimulates the release of what three things

D cell--> somatostatin ECL--> histamine Parietal Cell--> HCl

What stimulates and inhibits ECL cells to release histamine?

Stimulated by Ach | inhibitd by SST

What 1 thing does histamine stimulate the release of?

Parietal cell --> HCl

What 3 things stimulate release of HCL from parietal cells?

ACh, Histamine, Gastrin

Stomach acid content (H+) will ______ within an hour of eating a meal

drop, thus pH will rise

When do we see a rise in H+ secreation after a meal?

starts to rise about the same time it drops (d/t food buffering) so around 1 hour and peaks at 3

Role of IF?

VitB12 absorption

What digests fats?

salivary lipase from salivary glands | Gastric lipase from chief cells

Pepsinogen for protein digestion and is secreated from: secreation induced by: activated by:

Chief Cells  Secretion induced by acetylcholine (vagus and myenteric nerves),gastrin (G-cells), secretin (duodenum) and cholecystokinin (duodenum)  Activated by HCl or Pepsin via accessing active site

Mucous cells in stomach are made of

mucins, phospholipids, electorlytes, water

Funxtion of mucous in stomach

protection, lubriation

How does mucous protect stomach?

 HCO3; Neutralizes acid within mucous and is Released by superficial epithelial cells  Mucins also protective

What relseases HCO3 in stomach

superficial epitherlial clls

Stomach fnx in storage by |  Food in concentric circles stretches the stomach causing _____to relax stomach wall

“vasovagal reflex”

 Secreted digestive enzymes mixed with food by weak peristalic constrictor waves (mixing waves) initiated at _____stomach wall and propagated to the antrum

mid to upper

_____muscle contraction pushes food towards the mid stomach

Pylorus (retrograde)

How much food is released to duodenum at a time?

Only about a few milliliters of food is released into the duodenum (chyme)

When empyting the stomach: | Intense peristaltic contractions in stomach antrum begin in_____and propagate

mid-stomach

As stomach empties, the contractions start

further up the stomach wall

In stomach:  Stretching of the stomach wall by food stimulates_____ reflexes to increase activity of pylorus pump to empty stomach

myenteric

IN stomach emptying: | ____ stimulation of the pylorus pump.

Gastrin

In Duodenum to control emptying of stomach: |  Duodenum nerves send signal in response to

wall distension, mucosal irritation, and chyme | acidity and osmolality

Duodenal Signals sent through the____ nervous system, extrinsic nerves and vagus nerves in parallel to inhibit stomach contractions and increase tone of the pyloric sphincter.

enteric