Oral and Gastric Biochemistry Flashcards
What are the components of saliva? (3)
Salivary gland secretions
Microorganism products
Soluble food products
How much saliva is produced per day?
One liter
What is the purpose of saliva? (6)
Lubrication
Aids in digestion/enzymatic cleavage
Growth factors for epithelium
Neutralization of bacterial acids (bicarbonate)
Taste mediation
Defense against microbes
What is the innervation of the parotid, submaxillary/submanidbular and sublingual glands?
Parotid glands – CN IX
Submaxillary/submandibular – CN VII
Sublingual – CN VII
What are the primary secretions of the salivary glands? (3)
Ptyalin (alpha-Amylase)
Mucus
ECF
What types of ion balancing are the salivary glands responsible for? (4)
Na+ active absorption
Cl- passive absorption
K+ active secretion
HCO3 secretion
What specific salivary substances are responsible for bacterial defense?
Lysozyme
Peroxidase
Lactoferrin
IgA
Defensins
Mucins
Mechansims of lysozyme and what does it target?
Beta 1-4 Linkage Cleavage
NAM and NAG in peptidoglycan (gram positive walls)
NAG residues in fungal wall
Mechanism of peroxidase, lactoferrin, mucins
Peroxidase – Bromide and iodine
Lactoferrin – Iron sequestration
Mucins
Lubricants, antimicrobial, found throughout the GI tract
Highly O-glycosylated specific glycoproteins targeting Ser/Thr
What viruses are associated with saliva?
What conditions can be associated with xerostomia?
What other pathology should you be concerned with
HSV, HHVs, EBV, Mumps, Rabies, HIV
Cystic fibrosis
Sjorgen’s syndrome
Cancer of glands
What are the cell types of the gastric crypts?
Superficial epithelial cells
Mucous neck cells
Stem cell
Parietal cells
Chief cell
Endocrine cells
What are the phases of gastric secretion?
Cephalic phase
Gastric phase
Intestinal Phase
Which molecules are released by the vagus nerve release?
What do they affect?
ACh - Stimulates Parietal Cell, ECL cell; Inhibits D cell
Gastric releasing peptide - Stimulates G cell
What does the D cell secrete?
What affects its secretion?
What does it affect?
Somatostatin
Stimulated by HCl, Inhibited by ACh
Inhibits G cell, ECL cell, parietal cell
What do G cells release?
What affects its secretion?
What does its secretion affect?
Gastrin
Stimulated by GRP, Inhibited by somatostatin
Stimulates D cell, ECL, cell, Parietal cell
What do ECL cells secrete?
What affects its secretion?
What does its secretion affect?
Histamine
Stimulation by ACh, D cell somatostatin inhibition
Parietal cell HCl
What happens to the pH level of the stomach during a meal and digestion?
Food essentially buffers the acid and increases the pH
Emptying of stomach decreases pH and increased acid secretion
As stomach digestion ends, somatostatin reduces acid secretion, stabilizing the pH
What is released for fat digestion and from where?
Lingual lipase – Salivary glands
Gastric lipase – Chief cells
What is released for carbohydrase digestion?
Where?
Mechanism?
Amylase (Ptyalin) – Salivary glands
Cleaves Alpha 1,4 in glucose
What is released for protein digestion?
From where?
How they are activated and why is it necessary?
What do they target?
Pepsinogens – Chief Cells
Activated by HCl or activated Pepsin
Cleavage required to expose active site
Pepsin cleaves hydrophobic proteins
Where is stomach mucous from?
What is it composed of?
What is its function?
From mucous cells
Composed of Mucins, Phospholipids, Electrolytes, Water
Lubricates, Protects using bicarbonate and mucins
What is motor function of the stomach while storing food?
Which reflex is important?
Food in concentric circles stretching the stomach
Vasovagal reflex results in relaxation of wall
What motor function occurs in stomach during mixing and propulsion?
How does this affect digestion?
Where does the food move to?
How much is released at this time?
Mixing waves from peristalsis breaks non-covalent bonds of food
Allows access for protein based denaturation
Pylorus muscle contraction pushes food to mid stomach
Only a few millimeters of food released as chyme
How does emptying occur in the stomach?
What is regulation of this at the stomach and duodenal levels?
Intense peristaltic contractions in stomach anthrum begin mid-stomach and propagate down
Progressively contractions start higher up in stomach wall
Stomach level
Stretching of stomach wall stimulates myenteric reflex to increase pylorus pump
Gastrin also induces pylorus pump
Duodenal
Nerves in response to wall distension, mucosal irritation and chime acidity
Signals sent through ENS, extrinsic nerves and vagus nerves together inhibit stomach contractions and increase tone of pyloric sphincter
