Last DI

Question 1

enteroendocrine cells

Answer 1

Hormonal gastrointestinal regulation

-one cell surface faces GI tract lumen - stimulus encountered
-stimulation - opposite cell surface from GI tract lumen releasing hormone into bloodstream
-hormone travels in blood stream to target cells that can be in more than one body location and lead to excitatory or inhibitory reactions

Key hormones
1. gastrin
2. secretin
3. CCK
4. somatostatin

-G cells: secrete gastrin
-D cells: secrete somatostatin

Question 2

exocrine cells

Answer 2

enzyme and environmental factor secretions

-parietal cells: secrete HCl
-chief cells: secrete pepsinogen (enzyme) into stomach lumen to float freely
-enterochromaffin-like cells (ECL): secrete histamine (paracrine substance) into local cell area

Question 3

mucous cells

Answer 3

mucus secretions

-secrete mucus and bicarbonate into stomach lumen to form a protective layer lining surface of epithelial cells to combat HCl to prevent ulcers especially

Question 4

Gastric phase

Answer 4

food arrives in stomach - receptors detect increased distension & increase amino acids and peptides and decreased acidity

Question 5

neural gastric phase

Answer 5

parasympathetic and enteric stimulation
-increase HCl secretion
-increase gastric motility which leads to increased gastric emptying

Question 6

hormonal gastric phase

Answer 6

gastrin secretion
-increase HCl secretion
-increase gastric motility and relaxing of pyloric sphincter which leads to greater gastric emptying
-increase contraction of lower esophageal sphincter which leads to preventing regurgitation

Question 7

pepsinogen

Answer 7

inactive so it doesn’t digest stomach wall cells, converted to active pepsin by HCl, pepsin breaks polypeptides (proteins) into smaller peptide fragments and it best in a highly acidic environment

Question 8

HCl additional functions

Answer 8

-increase activity of lingual lipase
-decrease activity of salivary amylase
-partially denatures proteins by opening up structure to expose more SA for chemical digestion
-kills some pathogens

Question 9

How polypeptides are broken down

Answer 9

1. Chief cells secrete pepsinogen and parietal cells secrete HCl and intrinsic factor
2. HCl converts pepsinogen into active pepsin
3. pepsin breaks polypeptides into individual peptides

Question 10

Intestinal phase

Answer 10

food arrives in duodenum - receptors detect increase acidity, fats, amino acids, and distension

Question 11

enterogastric reflex (neural in intestinal phase)

Answer 11

-short reflexes: enteric and directly effecting stomach
-long reflexes: CNS (parasympathetic and sympathetic) changes indirectly effecting the stomach

Question 12

responses for intestinal phase

Answer 12

decreased gastric motility + increased contraction of pyloric sphincter = decreased gastric emptying to try and match small intestine digestion and absorption rates