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Nutritional Physiology > GIT Secretions > Flashcards

GIT Secretions Flashcards

1
Q

What are the different gastric cells? (Stomach) (5)

A
  • G cells
  • D cells
  • ECL cells
  • Chief cells
  • Parietal cells
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2
Q

What do parietal cells secrete?

A

Acid

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3
Q

What do G cells secrete?

A

Gastrin

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4
Q

What do D cells secrete?

A

Somatostatin

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5
Q

What do ECL cells secrete?

A

Histamine

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6
Q

What are secretory glands in the intestine called?

A

Crypts of Liberkün

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7
Q

What do chief cells secrete?

A

Pepsinogen

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8
Q

How does the control of gastric secretion work in the cephalic phase?

A
  • ACh is a strong stimulant for the release of acid and pepsinogen (parietal and chief cells)
  • ACh also activates ECL cells which release histamine to act on the parietal cell
  • ACh turns off D cells which normally produce somatostatin to inhibit gastrin production
  • ACh turns on G cells, gastrin activates ECL cell, parietal cell and D cell
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9
Q

What is the main stimulant for acid release?

A

Histamine

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10
Q

What happens to secretions in the gastric phase?

A
  • stretch of the stomach stimulates enteric NS - increases release of ACh
  • presence of food actively stimulates G-cells as well
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11
Q

Control of acid release: ACh

A

….

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12
Q

Somatostatin acts on parietal/chief cells through…….

A

Gi linked receptor, inhibits cAMP and PKA

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13
Q

What are the intestinal glands? (4)

A
  • goblet cells
  • S-cells
  • I-cells
  • Paneth cells
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14
Q

What do globlet cells produce?

A

Mucous

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15
Q

What do S-cells secrete?

A

Secretin

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16
Q

What do I-cells secrete?

A

Cholecystokinin

17
Q

What is the only intestinal enzyme?

A

Enteropeptidase: activates trypsinogen to trypsin

18
Q

Chyme is …….

A

Hypertonicity and pulls water out of intestinal cells

19
Q

What are the exocrine pancreatic cells?

A

Acinar cells

20
Q

Where do pancreatic enzymes enter the intestine?

A

Sphincter of Oddi

21
Q

What are the pro-enzymes secreted by the pancreas?

A
  • chymotrypsin
  • elastase
  • carboxypeptidase

Cleaved and activated by trypsin

22
Q

What are the active enzymes secreted by the pancreas? (5)

A
  • amylase
  • lipase
  • carboxyl lipase (cholesterol)
  • DNase
  • RNase
23
Q

How are pancreatic enzymes secreted?

A
  • zymogens stored in secretory vesicles
  • exocytosis - uses SNARE proteins
  • triggered by PKC and PKA calcium sensitisation of SNARE proteins
24
Q

How are pancreatic secretions inhibited?

A
  • somatostatin
  • cAMP
  • decreases PKA (Gi linked)
  • decreases calcium sensitisation
25
Q

What does PKC do in pancreatic secretion?

A

Phosphorylates SNARE proteins and reduces the conc. of calcium needed to activate exocytosis

26
Q

How is pancreatic fluid secreted? (5)

A
  1. Na/K ATPase creates sodium gradient (3 Na out, 2 K+ in)
  2. pump pumps Na(3), Cl(6) and K(3) in to cells
  3. K has channels so K does bog laps as usual
  4. Cl- diffuses our through apical membrane
  5. Pulls Na+ - para cellular route (+water)
27
Q

Pancreatic fluid cells have an unusually high concentration of…….

A

Chloride

28
Q

What stimulates pancreatic fluid release?

A

ACh, CCK - increase intracellular Ca2+ which opens apical chloride channel

29
Q

Pancreatic bicarbonate is made by the ……

A

Epithelial cells of pancreatic duct

30
Q

How is pancreatic bicarbonate secreted?

A
  1. CO2 moves in from basolateral surface
  2. Carbonic anhydrase makes bicarbonate and acid
  3. Acid is moved back across basolateral membrane through H+ ATPase pump and Na+/H+ antiport
  4. Bicarbonate is also transported directly in the cell with a bicarbonate/Na+ symport
  5. Bicarbonate leaves the cell using a Cl-/HCO3- antiport
  6. Chloride has transporters so it does bog laps on the apical membrane (cystic fibrosis transmembrane regulator CFTR)
31
Q

What is the regulated part of pancreatic bicarbonate release?

A

CFTR channel - secretin acts through Gs, ACh also has some effect (PKC, calcium…)

32
Q

What happens with pancreatic releases in the cephalic phase?

A

ACh stimulates release, gastrin release

33
Q

How does CCK affect pancreatic secretions in the intestinal phase?

A

Acts on acinar cells, also acts on nerves

Secretin acts only on bicarbonate receptors, no nerves

34
Q

What are the characteristics of bile?

A
  • made in liver
  • secreted into bile ducts
  • stored in gallbladder
  • primary bile salts made in gallbladder from cholesterol
  • secondary bile salts altered by bacteria in gut
35
Q

Where are bile salts reabsorbed?

A

Ilium

36
Q

What is the bile salts reuptake pathway?

A

Hepatocytes use Na+ bile salt symport and ATP powered organic anointed transporter, exported by bile salt export protein (BSEP)

37
Q

What controls release of bile salts?

A
  • cephalic and gastric: ACh and gastrin
  • intestinal: CCK

Causes contraction of gallbladder and relaxation of sphincter of Oddi

38
Q

How are bile salts concentrated?

A
  1. Na+/K+ pumps ions from apical membrane, through the cell and across the basal membrane
  2. Cl- moves across by osmosis
  3. Water follows
  4. Bile salts are concentrated

Nutritional Physiology (13 decks)

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