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Year1-Mubarak-LSS2 > Pancreas > Flashcards

Pancreas Flashcards

1
Q

Embryology

A
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2
Q

Draw a diagram of a pancreas ilustrating its different regions?

A
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3
Q

Briefly describe the relationship of the pancreas to other organs ?

How does pancreatic juice reach the duodenum?

A

Lies mainly on posterior abdominal wall extending from C-shaped duodenum to hilum of spleen

Pancreatic juice reaches duodenum via main (and accessory) pancreatic ducts

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4
Q

What is the arterial blood supply of the pancreas?

A

Close relations with (and supply from) coeliac and superior mesenteric arteries

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5
Q

What is the venous drainage of the pancreas?

A

Venous drainage of the head of the pancreas is into the superior mesenteric branches of the hepatic portal vein.

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6
Q

Further embryology

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7
Q

What cells make up the islets of langerhans and rank them based on amount?

A
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8
Q

Pancreas histology

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9
Q

Name the cell involved in the production of pancreatic juice and state what they produce?

Draw a diagram illustrating these cells

A
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10
Q

Why does the pancrease secrete bicarbonate?

What cells produce this bicarbonate?

A
  • Duct & centroacinar cells
  • Juice = RICH in bicarbonate ~ 120 mM (mmol/L) - (plasma ~25 mM). pH 7.5-8.0
  • Neutralises acid chyme from the stomach

–prevents damage to duodenal mucosa

–Raises pH to optimum range for panreatic enzymes to work

•Washes low volume enzyme secretion out of pancreas into duodenum

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11
Q

Why does bicarbonate secretion stop when pH is still acid?

A

Bile also contains bicarbonate and helps neutralise the acid chyme (liver functions lecture).

Brunners glands secrete alkaline fluid (Small intestine lecture).

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12
Q

State the mechanism for bicarbonate secretion in the pancreas

A

1. Pancreatic HCO3 Secretion

Catalysed by carbonic anhydrase

Separation of H+ and HCO3-

Na+ moves down gradient via paracellular (“tight” junctions)

H2O follows

2. Pancreatic HCO3 Secretion

Cl/HCO3 exchange at lumen

Na/H exchange at basolateral membrane into bloodstream

3. Pancreatic HCO3 Secretion

Na gradient into cell from blood maintained by Na/K exchange pump

Uses ATP - Primary active transport

4. Pancreatic HCO3 Secretion

K returns to blood via K-channel

Cl returns to lumen via Cl-channel

(cystic fibrosis transmembrane conductance regulator (CFTR)

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13
Q

Intersting aside

A
  • H2O + CO2 Û H2CO3 Û H+ + HCO3-
  • Same reaction in gastric parietal cells (acid) and pancreatic duct cells (alkaline)
  • In stomach, H+ goes into gastric juice, HCO3- into blood. Gastric venous blood is alkaline
  • In pancreas, HCO3- secreted into juice and H+ into blood. Pancreatic venous blood is acidic
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14
Q
A

The ezyme can degrade the pancreatic tissue- using zymogens can be thought as a protective mechanism

  • Enzymes for digestion fat (lipases), protein (proteases) and carbohydrates (amylase) are synthesised and stored in zymogen granules
  • Proteases are released as inactive pro-enzymes ~ protects acini and ducts from auto-digestion
  • Pancreas also contains a trypsin inhibitor to prevent trypsin activation
  • Enzymes become activated ONLY in duodenum
  • Blockage of pancreatic duct may overload protection and result in auto-digestion (= acute pancreatitis)

•

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15
Q

What enzyme does the duodenal mucosa secrete and what is its function?

A

Duodenal mucosa secretes an enzyme - Enterokinase (enteropeptidase) - that converts trypsinogen to trypsin.

Trypsin then converts all the other proteolytic and some lipolytic enzymes (note lipase secreted in active form but requires colipase, which is secreted as precursor)

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16
Q
A
17
Q

Look at kuracloud

A
18
Q

List the steps for the control of secretion?

What controls enzyme and bicarbonate secretion?

A

1

•Initial cephalic phase

–Reflex response to sight/smell/taste of food

–Enzyme-rich component only. Low volume - “mobilises” enzymes

•Gastric phase

–Stimulation of pancreatic secretion originating from food arriving in the stomach

–Same mechanisms involved as for cephalic phase

•Intestinal phase (= 70-80% of pancreatic secretion)

–Hormonally mediated when gastric chyme enters duodenum.

–BOTH components of pancreatic juice stimulated (enzymes + HCO3 - juice flows into duodenum)

2

  • The two components of pancreatic juice are separately controlled
  • Bicarbonate secretion is controlled by release of a hormone - Secretin (cAMP)
  • Enzyme secretion is controlled by vagal reflex and by a hormone - Cholecystokinin (CCK) (Ca2+/PLC)

CCK also stimulates bile secretion

19
Q

Outline the secretion of secretin

A
20
Q

Outline the secretion of cck

A
21
Q

Stimulus interaction

A
22
Q
  • So, during a meal……..
  • Food mixed, digested in stomach, pH 2
  • Chyme squirted into duodenum
  • H+ ions in duodenum stimulate release of ……………., stimulating release of pancreatic juice (plus bile and ………………. gland secretions) to raise pH to neutral/alkaline.
  • Peptides + fat in duodenum cause sharp rise in …………, ………….. nerve, stimulating pancreatic enzyme release, peaks by 30 mins, continues until stomach empty.
  • CCK potentiates effects of secretin on aqueous component (necessary because most of duodenum not at low pH).
A
  • So, during a meal……..
  • Food mixed, digested in stomach, pH 2
  • Chyme squirted into duodenum
  • H+ ions in duodenum stimulate release of secretin, stimulating release of pancreatic juice (plus bile and Brunner’s gland secretions) to raise pH to neutral/alkaline.
  • Peptides + fat in duodenum cause sharp rise in CCK, vagal nerve, stimulating pancreatic enzyme release, peaks by 30 mins, continues until stomach empty.
  • CCK potentiates effects of secretin on aqueous component (necessary because most of duodenum not at low pH).
23
Q

Summary

A
  • Endocrine pancreas = islets (tail)
  • Exocrine pancreas = acini + ducts
  • The pancreas has an important exocrine role in digestion.
  • Bicarbonate is released to neutralise the acid from the stomach. Release controlled by secretin.
  • Enzymes to digest proteins, fats and carbohydrates are released into the pancreatic duct (which merges with the common bile duct at the ampulla of Vater) and from there into the duodenum. Release controlled by the vagus nerve and by CCK

Year1-Mubarak-LSS2 (12 decks)

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