Pancreas; Anatomy and Secretions

Question 1

Pancreas exocrine functions

Answer 1

Acinar cells produce enzymes;
- amylase (for carbs)
- lipase (for lipids)
- trypsin (for proteins)
Releases these into duodenum at Ampulla of Vater through pancreatic duct
The duct is also lined with cells that secrete NaHCO3

Question 2

Pancreas endocrine functions

Answer 2

Islets of langerhans produce insulin (in B cells) and glucagon (in a cells)
Releases these directly into blood stream

Question 3

Fat digestion

Answer 3

Lipase
Triglyceride molecule too large to be absorbed, so pancreatic lipase hydrolyses into monoglyceride and free fatty acids.
Hydrolysis requires presence of bile acids

Question 4

Protein digestion

Answer 4

Pancreas releases trypsinogen, chymotrypsinogen and procarboxypolypeptidase pro-enzymes
This is activated by duodenal enterokinase to trypsin

Question 5

Trypsin roles

Answer 5

Activates all of the other pro-enzymes

Splits proteins into peptides of various sizes (most abundant)

Question 6

Carbohydrate digestion

Answer 6

Pancreas and salivary glands secrete amylase
Digest starch and gluycogen
Produces maltose and maltriose

Question 7

What happens to the maltose/maltiose after this

Answer 7

Small intestine brush border enzymes complete their digestion to glucose

Question 8

Anatomy of the ducts

Answer 8

At end, the acinar cells secrete the enzymes into acinus.
This travels down intercalated duct
These drain into larger interlobar, then extralobar ducts.
These then meet to form the main pancreatic duct, which joins the common bile duct

Question 9

Main pancreatic duct

Answer 9

Travels from tail to head (left to right)
Together w bile duct, opens into seconds part of duodenum at ampulla of vater
This opens into duodenum at major duodenal papilla

Question 10

Sphincters in the route

Answer 10

• Pancreatic duct sphincter at termination of pancreatic duct
• Hepatopancreatic sphincter (oddi) at ampulla of vater
  Control flow of pancreatic juice into duo

Question 11

Where and what level does the pancreas lie

Answer 11

Right side (head) lies across vertebral bodies of L1-L3. Ontop of IVC
Posterior to stomach and transverse mesocolon
Body lies ontop of aorta
Left (tail) is in contact with hilum of spleen

Question 12

What is the uncinate process

Answer 12

Small portion of head that curves around to the left

hooks around the superior mesenteric vessels

Question 13

Blood supply to the pancreas

Answer 13

Head - Anterior and posterior superior and inferior pancreatricoduodenal arteries
Remainder supplied by up to 10 branches of splenic artery

Question 14

Venous drainage of pancreas

Answer 14

To Portal
Splenic (most)
Superior mesenteric veins

Question 15

Innervation of the pancreas

Answer 15

From splanchnic nerves

Vagi through coeliac and superior mesenteric plexuses

Question 16

Protection of the pancreas from trypsin

Answer 16

If a little trypsin gets into pancreas then it would autodigest.
Therefore pancreas contains trypsin inhibitor called the kazal inhibitor.
Also acid pH maintenance prevents proenzymes being at their optimum pH

Question 17

How much fluid does the pancreas secrete a day

Answer 17

about 1.5 L

Bulk is NaHCO3 juice from small ducts, rest is digestive enzymes

Question 18

Function of the NaHCO3 released

Answer 18

Neutralise gastric acid in the duodenum to about pH 6 or 7

Question 19

How do the lining cells of duct form NaHCO3?

Answer 19

• CO2 from blood combines with H20 to form HNO3-
• HCO3- actively transported out into lumen via Cl-/HCO3- exchanger
• Na+ moves via paracellular pathway
• Cl- moves out into lumen by CFTR channel to keep gradient

Question 20

Conc difference between pancreatic juice HCO3- and blood

Answer 20

Bicarbonate in pancreatic juice is derived from blood, therefore its conc is proportional to that in the blood

Question 21

How do the H+ ions prduced get removed from the cell?

Answer 21

Via Na+/H+ exchanger into the blood.

The Na+ is then pumped back out into the blood by Na+/K+ pump

Question 22

Movement of water?

Answer 22

Movenemt of HCO3- and Na+ from blood into lumen causes an osmotic gradient, which drives water to move from blood into lumen.
Results in an almost isosmotic solution

Question 23

Role of bile

Answer 23

Breaks down fats into smaller pieces which are easier for lipase to digest

Question 24

Stimulation of pancreatic secretion

Answer 24

• Parasymp vagal stimulation (symp inhibits) increase enzyme and aqueous components secretion
• Secretin and CCK released from duodenal mucosa stimulate secretion of aqueous component

Question 25

1. Cephalic phase of pancreatic secretion

Answer 25

Minor in humans
Gastrin released from mucosa of antrum in reponse to vagal stimulation (Ach)
This causes a release of small amount of pancreatic juice w high protein content

Question 26

2. Gastric phase of pancreatic secretion

Answer 26

Gastrin released in response to gastric distention (vago-vagal reflex) and presence of aa in antrum
Continues to stimulate release of pancreatic juice
Vago-vagal reflexes act on receptors on acinar cells to release pancreatic juice w large enzyme amounts

Question 27

3. Intestinal phase of pancreatic secretion

SECRETIN

Answer 27

Longest and most important phase
Secretin released from duodenal mucosal cells in response to acid in lumen.
Secretin acts on pancreatic ducts to release large volume of HCO3- fluid.
Also stimulates bile production in liver

Question 28

3. Intestinal phase of pancreatic secretion

CCK

Answer 28

Also secreted from duodenal mucosa, in response to peptides, aa and fatty acids in lumen
Actions;
- on pancreatic acinar cells to stimulate enzyme synth and release
- on gallbladder to stimulate contraction and relaxation of the hepatopancreatic sphincter. allows release of bile into duo

Question 29

Somatostatin effect on pancreatic secretion

Answer 29

Inhibits adenylate cyclase and decreases cAMP.

Therefore inhibits secretion of acinar and duct cells