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Secretions Flashcards

1
Q

What is the function of saliva?

A

Digest starches (amylase) and lipids (lingual lipase) and lubricate foods (mucus)

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2
Q

What are the 3 glands that secrete saliva?

Which gland accounts for the majority of saliva secretion?

A

Parotid gland (serous only)
Submandibular (serous and mucus)
Sublingual (serous and mucus)
Mixed glands secrete a majority of saliva

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3
Q 
Explain the salivary gland structure with regards to:
Acinus
Myoepithelial cells
Intercalated ducts
Striated ducts
A

Acinus- secretes initial saliva
Myoepithelial cells- contract to eject saliva
Intercalated ducts- saliva at this point is isotonic
Striated ducts- lined with ductal cells and will secrete HCO3 and K into saliva and reabsorb NaCl

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4
Q

Why is saliva a hypotonic solution?

A

Ductal cells will reabsorb more NaCl than they secrete HCO3 and K
As well ductal cells are water impermeable

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5
Q

What are the main components of saliva? 6 components

A 
Water
Electrolytes 
A-amylase (starches)
Lingual lipase (lipids)
Kallikrien (increase blood flow during salivation)
Mucus (lubrication)
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6
Q

With regards to innervation, what makes salivary glands special?

A

Exclusively under ANS control

Parasymp and symp BOTH stimulate saliva secretion (para>symp)

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7
Q

Explain the parasympathetic innervation of salivary glands with regards to pre and post ganglionic fibers and where they synapse

A

Presynaptic- facial and glossopharyngeal nerves

Postsynaptic- fibers from ANS ganglia will synapse on individual cells

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8
Q

Explain the sympathetic innervation of salivary glands including pre and post synaptic fibers

A

Presynaptic- arise from cervical ganglion

Postsynaptic- extend to glands via periarterial spaces between cells

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9
Q

Explain parasympathetic pathway and regulation of salivary glands

A

Excitatory stimulus- food, nausea, smell
Inhibitory stimulus- dehydration, fear, sleep
Pathway- stimulus triggers facial/glossopharyngeal nerve to travel to glands and release Ach triggering glandular cells to secrete saliva
Atropine inhibits AchR from triggering saliva release

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10
Q

What cells are responsible for secreting “gastric juice”?

A

Parietal cells, chief cells, and mucus cells

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11
Q

What are the 4 major components of gastric juice?

A

HCl- initiates protein digestion and activates pepsin
Pepsinogen- released by chief cells and activated by low pH
Mucus- protects stomach and along with HCO3 helps neutralize acid
Intrinsic Factor- required for vit B12 absorption

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12
Q

What are the 2 types of gastric mucosa glands? Where are they located and what do they secrete?

A

Oxyntic gland- proximal 80% of stomach, secrete acid

Pyloric gland- distal 20% of stomach, release gastrin

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13
Q

What do parietal cells secrete and with what purpose?

A

Parietal cells secrete HCl to lower stomach pH to begin protein digestion and activate pepsin

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14
Q

Explain the mechanism of parietal cell HCl secretion

A

Within cell CO2 and water create H2CO3 which splits into H and HCO3
H is secreted into lumen via K/H antiporter
HCO3 is reabsorbed into blood via HCO3/Cl antiporter
Cl exits into lumen passively and joins H to create HCl

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15
Q

Explain actions of the following with regards to parietal cells:
Omeprazole
Cimetidine
Atropine

A

Omeprazole- inhibits H/K ATPase and is used to treat uclers

Cimetidine- histamine H2 receptor antagonist prevents histamine from stimulating H secretion and is used to treat ulcers and GERD

Atropine- inhibits M3 AchR from binding Ach released due to vagus stimulation

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16
Q

Explain the role of vagus nerve in parietal cell stimulation (direct and indirect stimulation)

A

Direct- vagus stimulates release of Ach which binds M3 AchR on parietal cells which triggers release of HCl (atropine inhibits this pathway)

Indirect- vagus stimulates release of GRP which binds G cells which stimulates secretion of gastrin which binds CCKR receptor on parietal cells and triggers HCl secretion

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17
Q

Explain potentiation with regards to parietal cells, specifically the roles of histamine, Ach, and gastrin

A

Histamine, Ach, and gastrin stimulate HCl secretion
Histamine potentiates affects of Ach and gastrin
Ach potentiates affects of histamine and gastrin

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18
Q

What are the 3 phases of HCl secretion and how much HCl secretion occurs with each phase?

A

Cephalic phase- 30%
Gastric phase- 60%
Intestinal phase- 10%

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19
Q

What are the stimuli for the cephalic phase of HCl secretion?

A

Stimuli- smell, taste, chew, swallow

20
Q

What is the mechanism of the cephalic phase of HCl secretion? Relate to vagotomy

A

Vagus n has the direct and indirect pathways of stimulating HCl secretion (direct-Ach binding M3 AchR on parietal) (indirect-GRP triggers gastrin release which stimulates parietal cells)

Vagotomy will abolish the cephalic phase of HCl secretion

21
Q

What are the stimuli for the gastric phase of HCl secretion?

A

Stimuli- stomach distention, presence of food

22
Q

What is the mechanism for the gastric phase of HCl secretion?

A

Distention- stimulates mechanoreceptors in mucosal glands which stimulate vagus nerve (direct and indirect pathways)

Antrum distention- activate pyloropyloric reflex which results in gastrin release which stimulates parietal cells to release HCL

Food- triggers gastrin secretion which stimulates parietal cells

23
Q

What is the mechanism of the intestinal phase of HCl secretion

A

Distend SI- secrete acid

Digested proteins- stimulate acid secretion

24
Q

What are the 2 “components” of gastric secretions?

A

Nonparietal and parietal

25
Q

What is nonparietal gastric secretions?

A

Constant, low volume alkaline secretion consisting of NaCl

26
Q

What is parietal gastric secretions?

A

Hyperosmotic solution of Cl

27
Q

Explain the relationship between gastrin, vagus n, and somatostatin

A

Somatostatin will inhibit G cells from secreting gastrin
Vagus n will release GRP trigger G cells to release gastrin and will inhibit somatostatin
Gastrin stimulates somatostatin release

28
Q

When is pepsinogen secreted from chief cells and oxyntic glands?

A

Pepsinogen is only secreted when the gastric pH is low enough to convert it to pepsin

29
Q

What cell secretes intrinsic factor?

What condition is associated with absence of IF?

A

Parietal cells secrete IF

Pernicious anemia is caused by parietal cell destruction resulting in IF not being secreted

30
Q

What are protective components of gastric mucosa?

A

HCO3, mucus, prostaglandins, blood flow, gastrin, and GF

31
Q

What are destructive components acting against mucosa?

A

Acid, pepsin, NSAIDs, H. Pylori, aspirin, bile, alcohol

32
Q

What are two common causes of peptic ulcers?

What are the two types of peptic ulcers?

A

Causes- H. Pylori and NSAIDs

Gastric and duodenal ulcers (duodenal more common)

33
Q

What is the cause of gastric ulcers?

A

H pylori releases cytotoxins that breakdown the protective barrier of the stomach and releases urease which promotes bacterial colonization of the mucosa

34
Q

What is the cause of duodenal uclers? What role does H pylori play?

A

Duodenal ulcers are result of abnormally high acid secretion

H pylori indirectly causes them by inhibiting somatostatin which usually regulates acid secretion

35
Q

What causes Zollinger-Ellison Syndrome? Why is it associated with steatorrhea?

A

A gastrin secreting tumor in pancreas causing excessive H secretion
The low pH inhibits pancreatic lipase which results in fatty stools

36
Q

What are the major components of pancreatic secretions?

A

Aqueous solution rich in HCO3 and enzymes

37
Q

With regards to pancreatic secretions, what does the acinar cells secrete?

A

Acinar cells secrete pancreatic amylases and lipases and inactive proteases which are activated in duodenum

38
Q

With regards to pancreatic secretions, what are the ductal secretions?

A

Ductal secretions are isotonic solution of ions which is modified to concentrate HCO3

39
Q

What special cell is associated with ductal cells of pancreas?

A

Centroacinar cells

40
Q

A mutation of what causes cystic fibrosis?

What is decreased as a result?

A

CFTR Cl channel mutation

Associated with decreased HCO3 secretion

41
Q

What are the 3 phases of pancreatic secretion?

A

Cephalic phase
Gastric phase
Intestinal phase

42
Q

What initiates cephalic phase of pancreatic secretion?

What is the secretion?

A

Initiated by smell and taste and mediated by vagus n

Secretion is enzymatic

43
Q

What initiates the gastric phase of pancreatic secretion?

What is the secretion?

A

Initiated by stomach distention and mediated by vagus n

The secretion is enzymatic

44
Q

What phase of pancreatic secretion accounts for a majority of the secretion?

A

Intestinal phase of pancreatic secretion

45
Q

What affect does sympathetic and parasympathetics have on pancreatic secretion?

A

Symp- inhibits

Parasymp- stimulates

46
Q

Where do postganglionic sympathetic fibers arise from with regards to pancreatic innervation?

A

Celiac and superior mesenteric ganglion

47
Q

Explain the intestinal phase of pancreatic secretion

A

Phe, Met, Trp, and FA stimulate I cells to secrete CCK which stimulates pancreatic secretions

H+ stimulates S cells to secrete secretin which stimulates HCO3 secretion

GI (10 decks)

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