Oral and Gastric Biochemistry

Question 1

What are the components of saliva? (3)

Answer 1

Salivary gland secretions
Microorganism products
Soluble food products

Question 2

How much saliva is produced per day?

Answer 2

One liter

Question 3

What is the purpose of saliva? (6)

Answer 3

Lubrication
Aids in digestion/enzymatic cleavage
Growth factors for epithelium
Neutralization of bacterial acids (bicarbonate)
Taste mediation
Defense against microbes

Question 4

What is the innervation of the parotid, submaxillary/submanidbular and sublingual glands?

Answer 4

Parotid glands – CN IX
Submaxillary/submandibular – CN VII
Sublingual – CN VII

Question 5

What are the primary secretions of the salivary glands? (3)

Answer 5

Ptyalin (alpha-Amylase)
Mucus
ECF

Question 6

What types of ion balancing are the salivary glands responsible for? (4)

Answer 6

Na+ active absorption
Cl- passive absorption
K+ active secretion
HCO3 secretion

Question 7

What specific salivary substances are responsible for bacterial defense?

Answer 7

Lysozyme
Peroxidase
Lactoferrin
IgA
Defensins
Mucins

Question 8

Mechansims of lysozyme and what does it target?

Answer 8

Beta 1-4 Linkage Cleavage
NAM and NAG in peptidoglycan (gram positive walls)
NAG residues in fungal wall

Question 9

Mechanism of peroxidase, lactoferrin, mucins

Answer 9

Peroxidase – Bromide and iodine

Lactoferrin – Iron sequestration

Mucins
Lubricants, antimicrobial, found throughout the GI tract
Highly O-glycosylated specific glycoproteins targeting Ser/Thr

Question 10

What viruses are associated with saliva?

What conditions can be associated with xerostomia?

What other pathology should you be concerned with

Answer 10

HSV, HHVs, EBV, Mumps, Rabies, HIV

Cystic fibrosis
Sjorgen’s syndrome

Cancer of glands

Question 11

What are the cell types of the gastric crypts?

Answer 11

Superficial epithelial cells
Mucous neck cells
Stem cell
Parietal cells
Chief cell
Endocrine cells

Question 12

What are the phases of gastric secretion?

Answer 12

Cephalic phase
Gastric phase
Intestinal Phase

Question 13

Which molecules are released by the vagus nerve release?
What do they affect?

Answer 13

ACh - Stimulates Parietal Cell, ECL cell; Inhibits D cell

Gastric releasing peptide - Stimulates G cell

Question 14

What does the D cell secrete?

What affects its secretion?

What does it affect?

Answer 14

Somatostatin

Stimulated by HCl, Inhibited by ACh

Inhibits G cell, ECL cell, parietal cell

Question 15

What do G cells release?
What affects its secretion?
What does its secretion affect?

Answer 15

Gastrin

Stimulated by GRP, Inhibited by somatostatin

Stimulates D cell, ECL, cell, Parietal cell

Question 16

What do ECL cells secrete?

What affects its secretion?

What does its secretion affect?

Answer 16

Histamine

Stimulation by ACh, D cell somatostatin inhibition

Parietal cell HCl

Question 17

What happens to the pH level of the stomach during a meal and digestion?

Answer 17

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

Question 18

What is released for fat digestion and from where?

Answer 18

Lingual lipase – Salivary glands
Gastric lipase – Chief cells

Question 19

What is released for carbohydrase digestion?
Where?
Mechanism?

Answer 19

Amylase (Ptyalin) – Salivary glands

Cleaves Alpha 1,4 in glucose

Question 20

What is released for protein digestion?
From where?
How they are activated and why is it necessary?
What do they target?

Answer 20

Pepsinogens – Chief Cells
Activated by HCl or activated Pepsin
Cleavage required to expose active site
Pepsin cleaves hydrophobic proteins

Question 21

Where is stomach mucous from?
What is it composed of?
What is its function?

Answer 21

From mucous cells
Composed of Mucins, Phospholipids, Electrolytes, Water
Lubricates, Protects using bicarbonate and mucins

Question 22

What is motor function of the stomach while storing food?
Which reflex is important?

Answer 22

Food in concentric circles stretching the stomach
Vasovagal reflex results in relaxation of wall

Question 23

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?

Answer 23

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

Question 24

How does emptying occur in the stomach?

What is regulation of this at the stomach and duodenal levels?

Answer 24

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