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BRS > Pancreas and small bowel > Flashcards

Pancreas and small bowel Flashcards

1
Q

Abdominal accessory organs start out as?

A

Foregut outgrowths.

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2
Q

How does the pancreas act as an exocrine gland?

A

Secretes pancreatic juice into the duodenum via main pancreatic duct.

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3
Q

What do acini in the pancreas do?

A

Secrete pro enzymes into ducts.

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4
Q

What do duct and centroacinar cells secrete into the pancreatic juice?

A

Bicarbonate ions.

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5
Q

What does bicarbonate in the pancreatic juice do?

A

Neutralises acid chyme from stomach which prevents damage to duodenal mucosa. Raises pH to optimum range for pancreatic enzymes to work.

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6
Q

What structures also produce bicarbonate instead of bicarbonate present in pancreatic juice?

A

Bile from liver and alkaline fluid from brunners glands.

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7
Q

How is bicarbonate secrete from pancreatic duct cells?

A

Carbonic anhydrase catalyses reaction of carbon dioxide with water to produce bicarbonate and H+ ions. Bicarbonate exchanged for chloride ion; bicarbonate enters lumen of duct while chloride enters duct cell. Sodium from blood enters duct cell while H+ enters blood.

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8
Q

How is high sodium in the blood maintained?

A

Na+/K+ exchange pump driven by ATP. Potassium into duct cell while sodium pumped into blood.

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9
Q

What drives water into lumen of pancreatic duct?

A

Sodium moves into lumen of duct down gradient from blood via paracellular junctions and water follows.

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10
Q

What channel drives chloride ions return to the lumen of the pancretic duct?

A

CFTR channel (cystic fibrosis transmembrane conductance regulator).

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11
Q

Why is pancreatic venous blood acidic but gastric venous blood is alkaline?

A

In pancreas H+ ions are released into blood. In stomach bicarbonate ions are released into blood.

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12
Q

Digestive enzymes in acinar cells are stored in what?

A

Zymogen granules.

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13
Q

Why are proteases released as inactive pro enzymes?

A

Protects acini and ducts from auto digestion.

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14
Q

What ensures that enzymes produced in pancreas are only activated once they enter the duodenum?

A

Trypsin inhibitor and enzymes are secreted as inactive pro enzymes.

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15
Q

Blockage of main pancreatic duct can result in what?

A

Auto digestion leading to acute pancreatitis.

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16
Q

What is the main enzyme that activates other proteolytic and lipolytic enzymes in the duodenum?

A

Trypsin.

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17
Q

What protein results in conversion of trypsinogen to trypsin? Where is this protein found?

A

Enterokinase secreted by duodenal mucosa. Found on the duodenal brush border.

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18
Q

What does lipase require for action?

A

Colipase and bile salts.

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19
Q

How do pancreatic secretions change based on diet?

A

Proportion of amylases and proteases changes depending on protein and carbohydrate ingestion.

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20
Q

Production of pancreatic digestion enzymes in response to sight/smell of food is what phase of pancreatic juice secretion?

A

Cephalic phase.

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21
Q

What is the gastric phase of pancreatic juice secretion?

A

Pancreatic juice secretion due to food arriving in the stomach.

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22
Q

During cephalic and gastric phase what is mainly secreted in the pancreatic juices?

A

Enzyme rich juice. Lacks carbonate.

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23
Q

What is the intestinal phase of pancreatic juice secretion? How is it different from the gastric and cephalic phase?

A

Hormone mediated when gastric chyme enters the duodenum. Both enzymes and carbonate released.

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24
Q

What stimulates enzyme secretion in pancreatic juice?

A

Acetylcholine from vagus nerve and cholecystokinin from duodenal I cells.

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25
Q

What controls bicarbonate secretion from duct and centroacinar cells?

A

Secretin.

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26
Q

What cells release cholecystokinin?

A

Duodenal I cells.

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27
Q

What stimulates release of cholecystokinin?

A

CCK releasing peptide due to increase in amino acid and fatty acids in lumen of duodenum. Gastrin releasing peptide.

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28
Q

What inhibits release of CCK?

A

Trypsin.

29
Q

Acinar fluid composition after leaving acini?

A

Isotonic.

30
Q

What stimulates release of acinar fluid?

A

Cholecystokinin.

31
Q

What triggers release of secretin from S cells?

A

Drop in pH in duodenum.

32
Q

When does CCK affect bicarbonate secretion?

A

When paired with secretin it can cause a large increase in bicarbonate secretion. On its own has no effect on bicarbonate secretion.

33
Q

Function of small bowel?

A

To absorb nutrients, salt and water.

34
Q

Small bowel parts?

A

Duodenum, jejunum and ileum.

35
Q

What is mesentery?

A

Tissue that suspends the small bowel and large bowel from the posterior abdominal wall.

36
Q

Function of mesentery?

A

Anchors small bowel and large bowel while still allowing for some movement. Conduit for blood vessels, nerves and lymphatic vessels.

37
Q

How is the mucosa layer of the small bowel adapted for maximal absorption?

A

Contain lots of villi that increase surface area.

38
Q

Where are villi innervated from?

A

Nerve plexus from submucosa layer.

39
Q

What cells cover villi?

A

Mostly enterocytes. Also have goblet and enteroendocrine cells.

40
Q

What cells are found at crypts of lieberkuhn?

A

Stem cells and paneth cells.

41
Q

How are enterocytes adapted?

A

Contain microvilli increase surface area even more.

42
Q

What kind of cells are enterocytes?

A

Columnar epithelium.

43
Q

What are the surface of microvilli covered with?

A

Glycocalyx.

44
Q

Function of glycocalyx?

A

Serves as protection from intestinal lumen. Controls rate of absorption from intestinal lumen.

45
Q

What does mucous do in the bowels?

A

Facilitates passage of material in bowel by acting as a lubricant.

46
Q

How does the number of goblet cells change as you go from the duodenum to the small bowel to the large bowel?

A

Increases.

47
Q

What do paneth cells do?

A

Regulate intestinal flora and engulf some bacteria.

48
Q

What do granules in paneth cells contain?

A

Lysozyme, glycoproteins and zinc.

49
Q

What do stem cells in the crypts do?

A

Migrate to the top of villus and replace older cells that have died by apoptosis.

50
Q

What distinguishes the duodenum from the jejunum and ileum?

A

Presence of brunner’s glands.

51
Q

What distinguishes the jejunum from the ileum?

A

Ileum has thin wall while jejunum has thick wall.

52
Q

What is the point of segmentation in regards to small bowel motility?

A

Mixed contents of lumen.

53
Q

What is migrating motor complex?

A

Cycles of smooth muscle contraction sweeping throughout the gut.

54
Q

Where does pancreatic amylase act and what does it digest?

A

Digestion of complex carbohydrates in lumen of small bowel.

55
Q

Where is pancreatic amylase secreted?

A

Duodenum.

56
Q

Factors for optimum pancreatic amylase activity?

A

Chloride ions and neutral pH.

57
Q

Where does digestion of simple carbohydrates occur at?

A

Brush border.

58
Q

Where does digestion of complex carbohydrates occur at?

A

Lumen.

59
Q

How are glucose and galactose absorbed?

A

Secondary active transport by SGLT1 (sodium/glucose cotransporter 1) carrier protein on apical membrane.

60
Q

How is fructose absorbed?

A

GLUT5 by facilitated diffusion on apical membrane.

61
Q

What transporter do simple sugar enter the interstitial space and then the blood?

A

GLUT2 on basolateral membrane.

62
Q

Where does protein digestion start? What digests it?

A

Lumen of stomach by pepsin.

63
Q

Where does carb digestion occur?

A

Mouth and small intestine.

64
Q

What inactivates pepsin?

A

Alkaline conditions of duodenum.

65
Q

What transporter on enterocytes absorb small peptides?

A

PepT1.

66
Q

What happens to small peptides absorbed by enterocytes?

A

Digested in the cytoplasm of the enterocytes. Intracellular digestion.

67
Q

What are the steps of lipid digestion?

A

Secretion of bile salts and pancreatic lipases. Emulsification of lipids. Lipase activated by co-lipase. Enzymatic hydrolysis of ester linkages. Solubilisation of lipolytic products in bile salt micelles (holds lipolytic products).

68
Q

What happens when monoglycerides and fatty acids enter the enterocytes?

A

Reconstructed back into triglycerides by Monoglyceride acylation, Phosphatidic acid pathway. Incorporated in chylomicrons and secreted across basement membrane by exocytosis into lymph vessel.

69
Q

Function of ileocaecal valve?

A

Allows passage of material into colon and prevents back flow of bacteria into ileum.

BRS (52 decks)

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