Gastrointestinal Secretions

Question 1

3 pairs of salivary glands

Answer 1

Parotid - serous fluid
Sublingual- mixed mucus and water
Submandibular - mucus

Question 2

Saliva contents (99.5% water)

Answer 2

• water
• electrolytes
• enzymes
  — α-amylase, lingual lipase, kallikrein -> bradykinin
• mucus
• antibacterial

Question 3

Ductal cells in intercalated duct function

Answer 3

modify secondary saliva by reabsorption of NA and Cl, and secretion of K and HCO3-

Question 4

5 functions of saliva

Answer 4

Digestion
Buffer
Solvent
Lubrication and binding
Oral hygiene

Question 5

Control of saliva secretion by the PsNS

Answer 5

Stimulation of salivatory nuclei in the medulla -> parasympathetic innervation via
- CNIX -> optic ganglion (ACh) -> muscarinic parotid gland stimulation.
- CNVII -> submandibular ganglion -> sunbmandibular/lingual gland stimulation.

Question 6

Stimulants/inhibitors of the salivatory nuclei
and associated nerves

Answer 6

Stimulated by sight, smell, touch, sound… Taste (VII/IX) and pressure (V) in mouth.
Inhibited by sleep, fatigue, fear

Question 7

Saliva secreted by SNS

Answer 7

Small amount that is thick and rich in mucus and enzymes (amylase)

Question 8

CNV
CNVII
CNIX

Answer 8

Vagal - mouth pressure
Facial - taste, subm/l glands
Glossopharyngeal - taste, parotid gland

Question 9

Xerostomia

Answer 9

Dry mouth, changed composition or reduced flow (hyposalivation).
Side effects of medication, radiation, diabetes, anxiety, Sjorgen’s syndrome
Treat with saliva substitutes, or drugs like pilocarpine that stimulate salivation.

Question 10

Gastric secretions composition

Answer 10

95% water
HCl
Intrinsic factor
Mucus
Enzymes (pepsin, gastric lipase)

Question 11

cells in the gastric pyloric gland

Answer 11

G-cells

Question 12

Gastric oxyntic gland cells

Answer 12

Parietal cells, chief cells, enterochromaffin cells.

Question 13

Chief cells

Answer 13

Secrete gastric lipase and pepsinogen that, when in low pH, is converted to pepsin.

Question 14

Tuft cells

Answer 14

Sense chemical signals and regulate immune responses.
Produce ACh to regulate gastric epithelial cell division and regeneration.

Question 15

Enteroendocrine cells include:

Answer 15

G-cells in the antrum
Enterochromaffin- like cells that secrete histamine
Enterochromaffin cells that secret 5-HT
D-cells that secrete somatostatin

Question 16

Parietal cells

Answer 16

Secrete HCl and intrinsic factor. HCl formed at the villus-like projections inside the canaliculi.

Question 17

Parietal cell important apical channels/transporters for secretion of HCl (3)

Answer 17

1. proton pumps: pump H+ into the lumen.
2. HCO3- exchanged for Cl- from the blood stream.
3. Cl- ions flow via Cl- ion channels into the lumen.

Question 18

3 hormones stimulating gastric acid secretion

Answer 18

Gastrin - G cells (gastrin/cck2 rec.)
Histamine - ECL cells (H2 rec.)
ACh - vagus nerve (m3 rec.)

Question 19

Cimetidines - tagament.
Ranitadines - zantac.

Answer 19

H2 receptor antagonists

Question 20

Prilosec and nexium

Answer 20

Proton pump inhibitors, most potent to reduce gastric acid secretion.

Question 21

Intrinsic factor

Answer 21

In the stomach, secreted by parietal cells.
Once chyme is neutralised and r-Protein breaks down in the duodenum, the IF binds vitamin B12. Travels to the ileum to receptors on ideal enterocytes for transfer to portal circulation.

Question 22

Perinicious anemia

Answer 22

Insufficient B12 absorption, failure of RBCs to mature (fatal).
Treat with V-B12 supplements, usually injected to bypass GI issues.

Question 23

Pancreatic fluid components

Answer 23

Water
Electrolytes (mostly Na and HCO3)
Enzymes (α-amylase, lipases, proteases)

Question 24

CFTR works with Cl-/HCO3- transporter

Answer 24

Pumps HCO3- into lumen in exchange for Cl- that then travels back out via the CFTR (cystic fibrosis transmembrane regulator).

Question 25

Regulation of pancreatic secretions by amino acids, peptides, and fatty acids

Answer 25

Occurs in acinar cells, potentiated by ACh Stimulation of I-cells causes release of CCK -> stimulates CCK1-R on acinar cells -> IP3 and Ca2+ act to stimulate release of enzymes

Question 26

Regulation of pancreatic secretion by acidity

Answer 26

Occurs in ductal cells, potential end by ACh and CCK Stimulation of S-cells causes release of Secretin -> stimulates S-R on ductal cells -> cAMP changes stimulate secretion of Na+ and HCO3-

Question 27

Bile composition

Answer 27

Water Electrolytes Bile acids Phospholipids (lecithin) Pigments (bilirubin) Cholesterol

Question 28

two functions of bile

Answer 28

1. digestion and absorption of fats 2. excreting blood waste products such as bilirubin and cholesterol.

Question 29

____% of bile salts are reabsorbed from t he ileum into the portal blood, and then are desecrated by the liver.

Answer 29

>90% A small fraction ends up reaching the colon where is undergoes dehydroxylation by colonic bacteria to form secondary bile salts that are then reabsorbed and resecreted.

Question 30

Gallstones

Answer 30

Composed of cholesterol mostly. Contributions; obesity, oral contraceptives, advanced age, sudden weight loss, genetics. Removal is fine as it is not essential.

Question 31

Crohn’s disease

Answer 31

An inflammatory bowel disease that causes cramps, diarrhea, weight loss, anemia… Causes included abnormal immune responses, genetics, environment. Surgery can remove up to 40% before complications - excretion of bile salts (loss) depleting pool and impairing fat absorption. Adverse effect on B12, iron, and calcium absorption.