Pancreas + Liver

Question 1

Structure of exocrine pancreas

Answer 1

Acinar-tubular

Question 2

Functions of pancreatic exocrine

Answer 2

1) Prod. of enzymes for fat, carb. + protein digestion

2) Control of duodenal pH, HCO3- neutralises HCl ; neutral pH allows pancreatic enzymes to act with optimal activity

Question 3

Protein digestion by pancreatic exocrine

Answer 3

Proteins are digested and secreted as inactive precursors in zymogen granules

Question 4

Breakdown of Trypsinogen

Answer 4

Activated to Trypsin by enteropeptidase in intestinal epithelium

Question 5

Pancreas produces X amount of Y fluid

Answer 5

X - 1.5 L/day

Y - Alkaline isotonic

Question 6

Mechanism of pancreatic secretion

Answer 6

1. Primary secretion : enzyme precursors from acinar cells + HCO3- from intralobular duct
2. Secondary modification : HCO3- / Cl- exchange in extra lobular ducts -> flow rate + ionic content

Question 7

Outline nervous control of pancreatic secretion

Answer 7

1. Vagal fibres
2. Acinar cells from s.m. of ducts + vessels
3. Mobilise proenzymes from cells into ducts
4. Blood flow increases via Ach release

Question 8

Secretin comes from

Answer 8

Duodenal epithelial cells at pH ,3.5

Question 9

Secretin effects

Answer 9

Duct cells produce watery fluids 4.5 x HCO3- then plasma -> neutralise chyme

Question 10

CCK comes from

Answer 10

Duodenal epithelial cells, stimulated by peptides, a.a.’s and f.a.’s

Question 11

CCK effects

Answer 11

Mobilise enzymes from acinar cells to lumen

Question 12

Gastrin effects

Answer 12

Increases fluid and enzyme secretion

Question 13

Phases of hormone secretion in digestion by pancreas

Answer 13

1. Cephalic phase (20%)
   - acinar cells, ducts
2. Gastric phase (10%)
3. Intestinal phase (70%)
   - HCO3- , Na+, H2O by secretin
   - CCK + gastrin -> acinar cells

Question 14

Liver secretion

Answer 14

600-1000ml/day isotonic fluid with bile acids, billnubin conjugates. phospholipid, cholesterol + electrolytes => active process

Question 15

Structure of bilary system

Answer 15

Canaliculi between hepatocytes drain into bile ducts at periphery of hepatic lobules. Bile ducts converge to form hepatic ducts -> bile to gallbladder

Question 16

Functions of bile

Answer 16

1. Digestion + absorption: formation of micelles

2. Excretion: excretion of large, hydrophobic products e.g. bile pigments from Hb breakdown

Question 17

Bile acid-dependent secretion

Answer 17

Active Na+ dependent retrieval of bile acids from portal blood + secretion into canalicular fluid

Question 18

Bile acid-independent secretion

Answer 18

Active secretion of NaCl + HCO3- into ducts with water flowing passively

Question 19

90-95% of bile salts are located

Answer 19

In enterohepatic circulation between liver and G.I. tract

-> mainly cholate + chenodeoxycholate

Question 20

2nd bile salts are in

Answer 20

Gut by bacteria -> deconjugate bile salts + free bile acids absorbed slowly by diffusion at al levels of s/l intestine

Question 21

Most bile acids conjugate with

Answer 21

Taurine / glycine with decrease pK values present in gut lumen as more soluble dissociated salts

Question 22

Functions of gall bladder

Answer 22

1. Storage of bile

2. Absorption of water + electrolytes across g.b. epithelium -> bile mroe concentrated

Question 23

Benefits of gall bladder

Answer 23

1. Doesn’t alter constituent ratio

2. Allows critical intracellular conc. to be exceeded

Question 24

Mechanism of bile release

Answer 24

Contraction of gall bladder smooth muscle + relaxation of Sphincter of Oddi -> bile into duodenum
- controlled by vagal + CCK mech in cephalic and intestinal phases