Pancreas and Liver

Question 1

What is the role of the exocrine pancreas and liver?

Answer 1

+ Accessory organs for intestines
- provide excretions (digestive enzymes, HCO3) directly into intestine lumen, to digest CHO, protein, lipid in small intestine

Question 2

What are the physical features of the pancreas?

Answer 2

+ Lies retroperitoneal (except tail), close to major blood vessels, difficult to access

+ Lies in C-shaped curve of duodenum with a head, neck, body, tail and uncinate process

Question 3

Where does the pancreatic blood supply come from?

Answer 3

+ Mainly via the splenic artery (from coeliac trunk)

+ Pancreatico-duodenal arteries (from SMA (superior mesenteric artery) or coeliac trunk)

Question 4

What are the primary functions of the exocrine pancreas?

Answer 4

+ Neutralise acid; digestive pro-enzymes secreted via pancreatic duct to 2nd part of duodenum

+ Deliver enzymes for macronutrient digestion in duodenum

Question 5

What are the acinar cells of the pancreas?

Answer 5

+ Main secretory cells
+ Clusters are connected by intercalated ducts
+ Converge on collecting ducts
+ Lining cells add ions and secretions

Question 6

What are the phases of digestion that exocrine pancreas regulation is dependent on?

Answer 6

+ Cephalic
+ Gastric
+ Intestinal

Question 7

What is involved in the cephalic phase of digestion?

Answer 7

Vagus nerve stimulates pancreatic secretions by releasing ACh and VIP

Question 8

What is involved in the gastric phase of digestion?

Answer 8

Medicated by vagovagal reflexes

Question 9

What is involved in the intestinal phase of digestion?

Answer 9

Controlled hormonally by secretin (in response to H+) and CCK (in response to aas, fatty acids, monoacylglycerols)

Question 10

What are the secretory cells involved with the exocrine pancreas?

Answer 10

+ Acinar cells

+ Ductal cells

Question 11

What is the role of zymogen granules, and where are they found?

Answer 11

+ They house inactive (and active) digestive enzymes

+ Secreted in respins to CCK (& VIP, gastric-releasing peptide)

+ Found in acinar cells

Question 12

What happens to zymogen granules upon activation?

Answer 12

They are exocytosed from acinar cells into luminal space

Question 13

What are features of acinar cells?

Answer 13

+ Basolateral CCK & ACh binding stimulates Cl- transport across apical mambrane.

+ Facilitates paracellular Na+ & water movement

Question 14

What are features of ductal cells?

Answer 14

+ Secretin & ACh bind in ductal cells

+ Activates cystic fibrosis transmembrance conductance
regulators, Cl- channels, Cl-HCO3- co-transporters.

+ Transporters recycle Cl- and HCO3-

Question 15

What is the effect of pancreatic secretion flow rate?

Answer 15

+ Alters ionic conentration: increased flow rate = HCO3- conc. increased, Cl- conc. decreased

+ Na+ and K+ conc. are not affected by flow rate

Question 16

What are the non-biliary liver functions?

Answer 16

+ Metabolism: pf CHO, protein, fat
- stores/releases CHO i.e glycogen (glycogenolysis, gluconeogenesis)

+ Detoxification:

• removal of ammonia and ethanol + drug biotransformations
• produces large amount of lymph

+ Immune system functions:
- removal of intestinal bacteria from portal blood so there is none in systematic circulation

Question 17

What are features of the liver?

Answer 17

+ Lies across the upper abdomen, under the diaphragm

+ Surrounded by peritoneum except for the bare area (related to diaphragm posteriorly)

+ May be palpable below the costal margin

+ Deep to its peritoneal covering, liver is completely surrounded by Glisson’s capsule

Question 18

What is Glisson’s capsule?

Answer 18

+ A thin connective tissue layer that sends extensions into the organ, inbetween the lobules

+ Not strong enough to hold sutures that may be required following trauma to the liver

Question 19

By which structures is the liver supplied?

Answer 19

+ Hepatic portal vein brings absorbed nutrients from stomach and gut
+ Hepatic portal artery supplies hepatocytes (liver cells) with oxygen

Question 20

How is bile drained from the liver?

Answer 20

+ Hepatocytes secrete bile into canaliculi, across series of bile ducts until they form the common hepatic duct

+ Bile flow from hepatocytes is in OPPOSITE direction of blood from hepatic artery and portal vein

Question 21

Via what structure is venous drainage?

Answer 21

Via hepatic veins that enter the inferior vena cava

Question 22

Describe the structure of the liver?

Answer 22

+ Left and right lobes (separated by falciform ligament)
+ Quadrate lobe next to gall bladder
+ Posterior surface shows caudate lobe next to IVC
+ Bare area is diaghragmatic surface of liver (no peritoneal covering)

Question 23

What are all of the functions of the liver?

Answer 23

+ Synthesis and secretion of bile

+ Storage (of glucose, glycogen, proteins, vitamins and fats)

+ Detoxification (of metabolic waste)

+ Synthesis of blood clotting (and anticoagulant factors (fibrinogen & prothrombin))

Question 24

What are some features of bile?

Answer 24

+ Bile pigments are derived as the breakdown products of haemoglobin; Kupffer cells (fixed phagocytes) play a role in their formamtion

+ Bile salts responsible for detergent and emulsifying effect of bile on fats

+ Increase absorption of fats by small intestine

Question 25

What are the constituents of bile?

Answer 25

\+ Bile pigments (chiefly bilirubin)
\+ Cholesterol
\+ Phospholipids 
\+ Fatty acids
\+ Water
\+ Electrolytes

Question 26

What are relations of liver between neighbouring structures?

Answer 26

\+ Right kidney and suprarenal gland
\+ Diaghpragm with lungs and pleura above (superior)
\+ Stomach, duodenum (posterior)
\+ Abdominal wall and ribcage (anterior)
\+ Hepatic fixture and transverse colon
\+ Gallbladder and portal triad

Question 27

How does the hepatobiliary system function?

Answer 27

+ Bile goes from common bile duct into duodenum or gallbladder

+ Sphincter of Oddi controls path into small intestine:

• contracted: gallbladder contraction forces bile down common bile duct
• relaxed: bile flows down common bile duct to duodenum

+ Sphincter relaxation regulated primarily by CCK

Question 28

What is the function of the gallbladder?

Answer 28

+ Stores and distributes bile - in concentrated form

+ Contracts to ecpel bile in response to CCK (same as Sphincter of Oddi to relax)

+ Vagal stimulation causes weak gallbladder contraction

+ Somatostatin & noradrenaline inhibit bile acid secretion

Question 29

What does exocrine pancreas regulation occur via?

Answer 29

+ Via stimulatory effects of secretin and CCK

+ Via inhibitory effetcs of somatostatin

Question 30

What is storage/secretion of substrates by the liver dependent upon?

Answer 30

The fed/fasted state

Question 31

What is the relationship between the pancreas and the stomach?

Answer 31

The pancreas is in direct contact with the stomach and connects to the duodenum via a collection of ducts - main & accessory pancreatic ducts - to openings (major & minor duodenal papilla)