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GI Block > GI Sectretions > Flashcards

GI Sectretions Flashcards

1
Q

What is a secretagogue? Name the three types used in the GI system?

A

Substance that stimulates cell to secrete.

neurocrine, endocrine, paracrine

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2
Q

neurocrine, endocrine, paracrine secretagogues. Explain

A

Neurocrine - NT from neuron innervating cell (vagal NT: ACh)
Endocrine - hormone (blood; gastrin)
Paracrine - (local; no blood; histamine)

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3
Q

Secretion - Blood Flow Coupling

A

More blood flow = more raw materials available to make and secrete whatever

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4
Q

Main Salivary Gland

A

Parotid

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5
Q

Structure of Salivary Glands

A

Acinus (contain serous/mucus glands)

Ducts - drainage and modification

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6
Q

Composition of Saliva?

A

Electrolytes, Water, Protein

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7
Q

Two stage model of salivary secretion?

Remember as Flow Rate increases –> do does secretion (always hypotonic) Na+ absorbing is flow dependent

A

1) Isotonic Primary Secretion at Acinus
2) Secondary Modification (Ducts):
Reuptake of Na+/Cl- for Secretion of K+/HCO3-
3) Secondary Secretion ⁃ Always hypotonic and alkaline

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8
Q

What type of proteins are found in saliva?

A

Mucin -aka MUCUS glycoprotein (viscosity -ubiquitous)
Enzymes (lipase, amylase)
IgA

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9
Q

Protective Function of Saliva?

A 
- HCO3-: Acid neutralization
⁃ Antimicrobials
⁃ IgA
⁃ Epidermal Growth Factor (heal)
⁃ Water intake (dry mouth)
⁃ Mouth Hygiene
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10
Q

Digestive Function of Saliva?

A

⁃ å-amylase/lingual lipase
⁃ R Proteins (Vit B12 binding protect against degradation)
⁃ Mucin glycoproteins - lube
⁃ Dissolving substances for taste mechanism

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11
Q

Regulation of Salivary Secretion?

A

Mostly Parasympathetic - vasodilation. Short lasting sympathetic - vasoconstricion; for both thing blood flow coupling.

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12
Q

Name the secretory cells found in the stomach?

What are of the stomach has no secretory cells?

A

Mucous Cells (2) [neck/grandular]
Parietal Cells - HCl, Intrinsic Factor (b12-binging)
Chief Cells - Pepsinogen, Gastric Lipase
Neuroendocrine Cells (3)

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13
Q

What are the neuroendocrine cells in the stomach? What is their function?

A

Function = regulation
G Cells - Gastrin
D Cells - Somatostatin
Enterochroaffin like Cells - histamine

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14
Q

Pepsinogen in stomach

A

at low pH cleaved to pepsin (protease). Pepsin cleaves pepsinogen.

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15
Q

Explain Cellular Mechanism of HCL production and Alkaline Tide

A

C. Anhydrase –> HCO3 (then dissociates)
⁃ H+/K+ ATPase drives H+ to lumen in exchange for K+ to inside cell.
⁃ Cl- electrogenic anion channel follows H+
⁃ HCO3-/Cl- exchange maintains Cl- supply
⁃ Alkaline tide: net HCO3- release into the blood circulation increasing pH of blood
during gastric acid secretion

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16
Q

What controls gastric secretion?

A

Neural: PS: via vagal nerve
Hormonal: Histamine, Gastrin - HCL, Secretin - Pepsinogen
Distension of duodenum

Secretin has (-) effect on acid secretion

17
Q

Explain Stimulation of acid in response to food (3)

A

Cephalic - smell, chewing taste
Gastric - Distension
Intestinal - Protein Digestion, disension, nutrients entering blood

18
Q

Gastric Mucosal Barriers (3)

A

1) bicarbonate rich layer
2) tight junctions
3) Luminal Membrabe

19
Q

What are three mechanisms that lead to peptic ulcers (doudenal/gastric)?

A

1) hyper-secretion of acid
2) effectiveness of gastric mucosal barrier
(stress = increased sympathetic tone)
3) infection by Helicobacter pylori
(inflammatory effects on mucosa)

20
Q

Pancreatic Secretory Contrebutions

Exocrine & Endocrine

name of pancreatic sphincter

A

Endocrine (PIGS) = insulin, glucagon, somatostatin

Exocrine = aqueous component, enzyme component

sphincter of oddi

21
Q

Aqueous secretions of the pancreas: Explain acid tide. and bicarbonate secretion

A

Aqueous Component: Isotonic HCO3- rich sol’n
• Incr [HCO3-] & Decr [Cl-] w/ incr’ing secr. rate
• HCO3- production: Carbonic Anhydrase
• HCO3- secr. > Lumen: HCO3-/Cl- exchngr
• Recycling of Cl-: Electrogenic Cl- Channel
• H+ Elimination from Lumen: Na+/H+ exchngr
⁃ Acid Tide: net H+ into Blood decr. pH

22
Q

Pancreatic Enzyme components breakdown ______. _______ is released by the duodenum and activates _______ from _______. a ______ in pancreatic secretions prevents premature activation of trypsin. ________ is a protein in pancreatic secretions that prevents inactivation of pancreatic lipase by bile salts

A

lipases, proteolytic, nucleolytic, amyloytic. Enterokinase/Enteropeptidase
Trypsin from Trypsinogen
Trypsin inhibitor
Colipase

23
Q

Describe the neural and hormonal control of pancreatic secretion:

A

Neural: Parasympathetic (Vagal, Ach): Stimulatory; Sympathetic: by vasoconstriction mediated decr. in secretion

Hormonal:
⁃ Secretin: HCO3-**
⁃ CCK: Enzyme Secretion**

other secretagogs

24
Q

Bile is made from _____ by ______; composition includes: ______, bile acids are conjugates of _____ and _____. Bile salts are more soluble than bile _____. They aid in absorption of ______. 95% are reabsorbed in the ______.

A

Cholesterol, Hepatocytes
Bile Salts, Pigment (bilirubin), Cholesterol, Phospholipids, Proteins (IgA), Electrolytes (isot.)
Taurine or Glycine; Acids; cholesterol (only); ileum

25
Q

Bile Transport (Reabsorption)

A

Conjugated - Actively Transported (Na - Co-transport); un-conjugated - Diffusion

Bacteria in ilium and colon un-conjugate bile salt.

26
Q

Bilirubin is the product of _______. Explain. Bilirubin is used to make ______. It is taken up from the systemic circulation by ______ and can be excreted by kidneys of SI. Jaundice occurs when ______

A 
Heme Degradation (heme(bilirubin+Iron)/ globin
Bile; Hepatocytes; Bilirubin in plasma is high!
27
Q

Bile Regulation (release by gallbladder)

A

Feedback of bile salt synthesis/secretion by [bile salt] in hepatic portal blood
• CCK**, Gastrin
• Neural Control: Both

28
Q

Intestinal Secretion (mucin (bicarbonate), electrolytes, water; Describe protective fxn of intestinal secretion.

  • volume of secretions are smaller in small intestine.
A
  • Maintain fluidity of chyme (water)
  • Dilution of toxic products (water)
  • HCO3-
  • Lubrication and protection (mucus)
29
Q

What stimulates gastric secretions?

A

Stimulated by intraluminal pressure, VIP, and toxins.

GI Block (23 decks)

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