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GI System > Pancreatic exocrine secretions and control > Flashcards

Pancreatic exocrine secretions and control Flashcards

1
Q

What is the exocrine portion of the pancreas?

A

Acinar and Duct Cells

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2
Q

What is the endocrine portion of the pancreas?

A

Islets of Langerhans

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3
Q

What is the role of acinar cells?

A

Secrete digestive enzymes (stimulated by CCK) to break down fats, carbohydrates, proetins and nucleic acids

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4
Q

What ius the role of duct cells?

A

Secrete aqueous NaHCO3 solution (stimulated by secretin)

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5
Q

Describe the Flow of pancreatic juice.

A

Ascini (cluster of ascinar cells) contain microvilli that extend into smallest ducts caused the intercalated ducts.

Intercalated ducts lead onto intralobular ducts, lined by cuboidal epithelial cells.

Intralobular ducts lead onto interlobular ducts lined by columnar epithelium and goblet cells.

Interlobular ducts lead onto the pancreatic duct, which enters the duodenum at common bile duct.

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6
Q

What happens to pancreatic juices as they flows through the ducts?

A

Their composition may be changed

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7
Q

Describe the composition of pancreatic juices.

A

1.5L fluid produced a day containing:

  • Na+
  • HCO3-
  • Albumin
  • Globulin
  • Digestive Enzymes
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8
Q

In what form are pancreatic enzymes secreted?

A

Secreted in an inactive form as zymogens to prevent autodigestion

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9
Q

Where are pancreatic enzymes activated?

A

Duodenum

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10
Q

What ions are secreted in the pancreatic juices?

A

HCO3-
Cl-
SO42-
HPO42-

Na+
K+
Ca2+
Mg2+

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11
Q

What is pancreatic fluid secreted by if rate of secretion is low?

A

Intralobular ducts

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12
Q

What effect does secretin have on the pancreas?

A

Increases output of pancreatic juice rich in bicarbonate ions

decreases output of pancreatic juice rich in chloride ions

also fall in amylase

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13
Q

What enzymes are secreted from the pancreas?

A

3 major types of enxzymes released:

  • Proteolytic Enzymes (trypsin, chymotrypsin, carboxypeptidase)
  • Amylase
  • Lipase

Other enzymes:

  • ribonucelase
  • deoxyribonuclease
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14
Q

What are proteolytic enzymes?

A

Enzymes that break down proteins

these enzymes are secreted as zymogens to prevent autodigestion

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15
Q

How is trypsinogen activated?

A

Converted to trypsin by enterokinases within the brush border of the duodenum

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16
Q

What is the role of amylase?

A

Enzyme that breaks down carbohydrates, converting polysaccharides to disacchardies

17
Q

What is the role of lipases?

A

Enzymes that break down lipids, converting triglycerides to fatty acids and glycerol

18
Q

What will pancreatic insufficiency of lipase cause?

A

lead to malabsorption of fat, causing steatorrhoea

19
Q

What is the Percentage of secreted enzymes that reach the small intestine?

A

Amylase- 75%
Trypsin- 20%
Lipase- 1%

20
Q

Describe the control of pancreatic secretion.

A

Neuroendocrine signals

Vagal parasympathetic stimulation
-enhances rate of secretion of enzymes and aqueous components of pancreatic juice

Sympathetic stimulation
-inhibits secretion

Secretin and CCK
-stimulate secretion of pancreatic fluid (enzyme and bicarbonate rich secretion)

21
Q

What are the phases of pancreatic secretion?

A
  1. cephalic phase
  2. gastric phase
  3. intestinal phase
22
Q

What is the cephalic phase of pancreatic secretion?

A

Sight/smell food causes vagal stimulation (Ach and VIP) of gastrin release from antrum, which promotes protein rich pancreatic juice

23
Q

What is the Gastric Phase of pancreatic secretion?

A

Distension causes vagal reflex on fundus or antrum and amino acids/peptides stimulate gastrin release, which promotes enzyme rich pancreatic juice

24
Q

What is the Intestinal Phase of pancreatic secretion?

A

Under influence of CCK and Secretin, where acidic chyme in the duodenum and jejunum induces secretion of pancreatic juice

25
Q

What are secretin and CCK released by?

A

Duodenal and jejunal mucosal cells

26
Q

What cells does secretin induce?

A

Secretin induces pancreatic duct cells to secrete HCO3- rich pancreatic juice

Secretin also stimulates production of bile by the liver

27
Q

What cells does CCK induce?

A

CCK stimulates pancreatic acinar cells to synthesize and release enzyme rich pancreatic juice

Also stimulates secretion of concentrated bile from gallbladder for fat absorption by contracting gallbladder and relaxing Sphincter of Oddi to release bile into duodenum

28
Q

What is the effect of cystic fibrosis on the pancreas?

A

Thick mucus obstructs pancreatic duct, causing pancreatic insufficiency.

Consequences are:

  • severe malabsorption
  • steatorrhoea
  • recurrent chest infections
  • sterility of males (vas deferens fails to develop properly)

GI System (15 decks)

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