GI Physiology

Question 1

Name the cell source for the following GI hormones: Gastrin, cholecystokinin, secretin, somatostatin, glucose-dependent insulinotropic peptide.

Answer 1

G cells (antrum of stomach), I cells (duodenum, jejunum), S cells (duodenum), D cells (pancreatic islets, GI mucosa), K cells (duodenum, jejunum)

Question 2

State whether GASTRIN inc/dec the following: gastric H+ secretion, growth of gastric mucosa, gastric motility.

Answer 2

Inc; inc; inc

Question 3

Stomach distention/alkalinization, amino acids, peptides, vagal stimulation inc/dec gastrin; stomach pH <1.5 inc/dec gastrin

Answer 3

Inc; dec

Question 4

Gastrin is increased in which syndrome?

Answer 4

Zollinger-Ellison syndrome

Question 5

Which 2 amino acids are potent stimulators of gastrin?

Answer 5

Phenylalanine and tryptophan

Question 6

State whether CCK inc/dec the following: pancreatic secretion, gallbladder contraction, gastric emptying, Sphincter of Oddi relaxation.

Answer 6

Inc; inc; dec; inc

Question 7

Fatty acids and amino acids inc/dec CCK.

Answer 7

Inc

Question 8

State whether SECRETIN inc/dec the following: pancreatic HCO3- secretion, gastric acid secretion, bile secretion.

Answer 8

Inc; dec; inc

Question 9

Acid, fatty acids in lumen of duodenum inc/dec secretin.

Answer 9

Inc

Question 10

State whether SOMATOSTATIN inc/dec the following: gastric acid and pepsinogen secretion, pancreatic and small intestine fluid secretion, gallbladder contraction, insulin and glucagon release.

Answer 10

Dec; dec; dec; dec

Question 11

Vagal stimulation inc/dec somatostatin; acid inc/dec somatostatin.

Answer 11

Dec; inc

Question 12

State whether GIP inc/dec the following: gastric H+ secretion (exocrine), insulin release (endocrine).

Answer 12

Dec, inc

Question 13

Fatty acids, amino acids, and oral glucose inc/dec GIP.

Answer 13

Inc

Question 14

State whether VIP inc/dec the following: intestinal water and electrolyte secretion, relaxation of intestinal smooth muscle and sphincters.

Answer 14

Inc; inc; dec; inc

Question 15

Adrenergic input inc/dec VIP; distention and vagal stimulation inc/dec VIP

Answer 15

Dec; inc

Question 16

T/F: A VIPoma is a non-alpha, non-beta islet cell pancreatic tumor.

Answer 16

TRUE

Question 17

VIPoma presents with watery diarrhea, achlorhydria, and hyper/hypokalemia.

Answer 17

Hypokalemia

Question 18

Nitric oxide inc/dec smooth muscle relaxation, including lower esophageal sphincter.

Answer 18

Inc

Question 19

Motilin is inc/dec in fasting state.

Answer 19

Inc

Question 20

T/F: Erythromycin is a motilin receptor agonist used to stimulate intestinal paralysis.

Answer 20

TRUE

Question 21

_____ cells produce intrinsic factor and gastric acid.

Answer 21

Parietal

Question 22

Intrinsic factor is a vitamin _____ binding protein required for uptake in the _____.

Answer 22

B12; terminal ileum

Question 23

What 2 conditions are associated with autoimmune destruction of parietal cells?

Answer 23

Chronic gastritis and pernicious anemia

Question 24

Gastric acid inc/dec stomach pH; inc/dec by histamine, ACh, gastrin; inc/dec by somatostatin, GIP, prostaglandin, secretin.

Answer 24

Dec; inc; dec

Question 25

What tumor causes continuous high levels of acid secretion and ulcers?

Answer 25

Gastrinoma

Question 26

Pepsin is produced by _____ cells and aids in carbohydrate/protein secretion.

Answer 26

Chief; protein

Question 27

Vagal stimulation and local acid inc/dec pepsin.

Answer 27

Inc

Question 28

_____ converts inactive pepsinogen to pepsin.

Answer 28

H+

Question 29

HCO3- is produced by _____ cells and _____ glands.

Answer 29

Mucosal (stomach, duodenum, salivary glands, pancreas); Brunner's (duodenum)

Question 30

Pancreatic and biliary secretion with secretin inc/dec HCO3-.

Answer 30

Inc

Question 31

Saliva is a secretion from which 3 glands?

Answer 31

Parotid, submandibular, and sublingual glands

Question 32

Saliva is stimulated by sympathetic activity only.

Answer 32

FALSE: sympathetic AND parasympathetic

Question 33

In saliva, _____ digests starch; _____ neutralizes acid; _____ lubricate food.

Answer 33

Amylase; HCO3-; mucins

Question 34

Saliva is normally hypo/hypertonic d/t absorption but more hypo/isotonic with higher flow rates.

Answer 34

Hypotonic; isotonic

Question 35

_____ blocks vagal stimulation of parietal cells.

Answer 35

Atropine

Question 36

Gastrin increases acid secretion through it's effect on _____ cells, leading to _____ release.

Answer 36

ECL; histamine

Question 37

Brunner's glands secret acidic/alkaline mucus.

Answer 37

Alkaline

Question 38

Hypertrophy of Brunner's glands is seen in which disease?

Answer 38

Peptic ulcer disease

Question 39

In pancreatic secretions, the fluid is hypo/isotonic; low flow leads to high _____ while high flow leads to high _____.

Answer 39

Isotonic; Cl-; HCO3-

Question 40

Alpha-amylase digests _____.

Answer 40

Starch

Question 41

Lipase, phospholipase A, colipase digest _____.

Answer 41

Fat

Question 42

Proteases digest _____.

Answer 42

Protein

Question 43

Proteases are secreted as proenzymes, also called _____.

Answer 43

Zymogens

Question 44

Trypsinogen is converted to active enzyme trypsin by _____; involved in a positive/negative feedback loop.

Answer 44

Enterokinase/enteropeptidase (from duodenal mucosa); positive

Question 45

Salivary amylase starts digestion, hydrolyzes alpha-1,4 linkages to yield _____.

Answer 45

Disaccharides (maltose and alpha-limit dextrins)

Question 46

Pancreatic amylase hydrolyzes starch to _____ and _____.

Answer 46

Oligosaccharides and disaccharides.

Question 47

Where is the highest concentration of pancreatic amylase found?

Answer 47

Duodenal lumen

Question 48

What is the rate-limiting step in carbohydrate digestion?

Answer 48

Oligosaccharide hydrolases

Question 49

T/F: Only monosaccharides (glucose, galactose, fructose) are absorbed by enterocytes.

Answer 49

TRUE

Question 50

Glucose and galactose are taken up by _____; fructose is taken up by _____; all are transported to blood by _____.

Answer 50

SGLT1; GLUT-5; GLUT-2

Question 51

What does the D-xylose absorption test tell you?

Answer 51

Distinguishes GI mucosal damage from other causes of malabsorption.

Question 52

Where is iron absorbed?

Answer 52

Absorbed as Fe2+ in duodenum

Question 53

Where is folate absorbed?

Answer 53

Jejunum

Question 54

Where is B12 absorbed?

Answer 54

Terminal ileum (along with bile acids, requires intrinsic factor)

Question 55

Where are Peyer's patches found?

Answer 55

Lamina propria and submucosa of ileum

Question 56

B cells stimulated in germinal centers of Peyer's patches differentiate into _____-secreting plasma cells.

Answer 56

IgA (*Remember Intra-gut Antibody mnemonic!)

Question 57

Bile is composed of which 6 substances?

Answer 57

Bile salts, phospholipids, cholesterol, bilirubin, water, ions

Question 58

Name 3 functions of bile.

Answer 58

Digestion and absorption of lipids and fat-soluble vitamins; cholesterol excretion; antimicrobial activity

Question 59

Bilirubin is removed from blood by _____; conjugated with _____; and excreted in _____.

Answer 59

Liver; glucuronate; bile

Question 60

Is direct bilirubin conjugated/unconjugated; water soluble/insoluble?

Answer 60

Conjugated (with glucuronic acid); water soluble

Question 61

Is indirect bilirubin conjugated/unconjugated; water soluble/insoluble?

Answer 61

Unconjugated; water insoluble

Question 62

Bile is excreted in feces as _____; excreted in urine as _____.

Answer 62

Stercobilin; urobilin