Intestine, Pancreas, Liver, Gallbladder Secretions

Question 1

Duodenum

Answer 1

receives stomach contents, pancreatic juice and bile, neutralizes stomach acids, emulsifies fats, pepsin inactivated by pH increase, pancreatic enzymes

Brunner’s glands - empty into intestinal glands and secrete alkaline fluid (coats duodenum)

Question 2

jejunum

Answer 2

most nutrient absorption occurs here

Question 3

Ileum

Answer 3

peyer’s patches – aggregated lymphoid nodules

Monitors intestinal bacterial populations and prevent growth of pathogenic bacteria in intestine

Question 4

Villi

Answer 4

fingerlike projections 1 mm tall
contain blood vessels and
lymphatics (lacteal)
nutrient absorption

Question 5

Microvilli

Answer 5

1 micron tall; 
	cover surface
brush border on cells
brush border enzymes for 
final stages of digestion

Question 6

Crypt-villus

Answer 6

functional unit of the small intestine. Stem cell division produces immature cells in crypts of Lieberkühn (intestinal gland) which secrete fluid; mature cells at the villus tip absorb nutrients, electrolytes, and fluid.

Question 7

Crypt villus unit

Answer 7

Villus tip - fully differentiated and undertake nutrient reabsorption

Maturation zone - intermediate where cells begin to express enzymes and absorptive membrane transport

Crypt - rapidly dividing stem cells that fore migration up villus

Question 8

Villi secretion

Answer 8

Goblet cells (mucus- lubricates and protects intestinal surface)
Enterocytes with brush border - enzymes

Question 9

Crypt of Lieberkuhn secretion

Answer 9

Intestinal glands and crypts
Paneth cells (lysozyme)
Enterocyte
Enteroendocrine cells

Question 10

Enteroendocrine cells

Answer 10

I (CCK-Cholecystokinin- stimulates gallblader to release bile)
D (somatostatin)
S (secretin –stimulates pancreas to release acid neutralizer bicarbonate )

Question 11

Celiac sprue

Answer 11

malabsorption syndrome - hypersensitivity to wheat gluten and gliadin

Question 12

Pancreas function

Answer 12

Secrete alkaline fluid that neutralises the acidic chyme

Secrete enzymes that breakdown macromolecules
Highest digestive power

Question 13

Pancreas - exocrine glands

Answer 13

Made up of acinus (digestive enzyme secretion) and duct (bicarbonate secretion)

Secretion delivered to duodenum via large pancreatic duct
Isotonic bicarbonate to intestinal lumen

Question 14

Pancreas - endocrine glands

Answer 14

4 types of islet cells that release hormones

Question 15

Pancreatic juice composition

Answer 15

Proteolytic enzymes: trypsinogen 1, 2 & 3, proelastase 1 & 2, chemotrysinogen

Lipolytic enzymes: Lipase Phospholipase A2, Pancreatic lipase

Nuclease: DNase and RNase

Amylolytic enzyme

Question 16

Regulation of pancreas enzyme secretion

Answer 16

Ach: Bind muscarinic receptor on acing cells -> Increase BF and gastrin

CCK: Released from duodenal I cells when food enters

Question 17

Regulation of pancreas alkaline secretion

Answer 17

Secretin - Released by S cells in duodenum and stimulated by low pH as food enters -> secretin enters blood - ductal cells

pH rarely low enough to stimulate high levels of secretin
Ducts become hypersensitive to low levels of CCK

Question 18

Mechanism of enzyme

secretions by acinar cells

Answer 18

Inactive proenzyme on ribosomes and transferred to rER - Golgi complex and acidic condensing vacuoles and zymogen granules

Stimulation of agonist (CCK or Ach or Secretin) = release content into lumen via intracellular 2nd messenger

Fusion and exocytosis of zymogen granules -> move to apical membrane and fuse with plasma membrane and discharge content

Question 19

Prevent autodigestion

Answer 19

Most enzymes = inactive precursor = zymogen

Enzyme sequestered in membrane-limited vesicles

Activate zymogen occurs in small intestine and process depends on conversion of proenzyme trypsinogen.

Enterokinase - bound to apical membrane of enterocyte lining

Question 20

Pancreatitis

Answer 20

Pancreatic enzyme activated within pancreas = auto digestion of tissues

Question 21

Duct cell secretions purpose

Answer 21

Neutralise acidic chyme entering duodenum

Question 22

HCO3 secretion by ductal cell

Answer 22

Secreted into cell cytoplasm by Cl-/HCO3- exchange in luminal cell membrane

Cl- recycled = supply enough intracellular cl- to sustain rate of cl-/HCO3- exchange

Na+ secreted into duct following HCO3- secretion - water follows