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GI-Final > Secretions Of The GI Tract & Pancreas-1/22/16 > Flashcards

Secretions Of The GI Tract & Pancreas-1/22/16 Flashcards

1
Q

___ cells of the salivary gland secrete initial saliva

When stimulated by neural input, ____ cells contract to eject saliva into the mouth

The ___ duct contains myoepithelial cells and saliva in this duct is similar in ionic composition to plasma

A

Acinar

Myoepithelial

Intercalated duct

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2
Q

The ___ duct is lined by columnar epithelial cells and modify the initial saliva to produce the final saliva that is HYPOTONIC

A

Striated

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3
Q

___ is a protease involved in the production of bradykinin (vasodilator)

A

Kallikrein

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4
Q

The formation of isotonic, plasma-like saliva is done by ___ cells

The modification of this isotonic solution is later done by the ___ cells

A

Acinar

Ductal

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5
Q

In the mechanism of salivary secretion, ___ is secreted into the lumen and ____ is reabsorbed into the bloodstream

A

HCO3 and K are secreted

Na and Cl are reabsorbed

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6
Q

List the transporters on the luminal (apical) membrane for salivary secretion/reabsorption

A

Na-H exchanger (Na reabsorbed, H secreted)
Cl-HCO3 exchanger (Cl reabsorbed, HCO3 secreted)
H-K exchanger (H reabsorbed, K secreted

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7
Q

Patients with cystic fibrosis have a defect in this channel:

A

Cyclic AMP-activated CFTR channel (secretes both Cl and HCO3)

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8
Q

How does saliva become hypotonic as it flows through the ducts?

A

Ductal cells are impermeable to water

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9
Q

At decreased flow rates, final saliva has lower concentration(s) of ___ and higher concentration(s) of ___

A

Na and Cl

K

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10
Q

What ganglion does the pre-synaptic fibers of the facial nerve synapse on? Where does the post-synaptic fiber travel to for synapsing?

A

Pre-ganglionic travels on Facial Nerve and synapses on Submandibular ganglion –> Post ganglionic travels and synapses on both Submandibular and Sublingual glands

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11
Q

What ganglion does the parasympathetic pre-synaptic fibers of the glossopharyngeal nerve synapse on? Where do the post-ganglionic fibers synapse?

A

Preganglionic travels on Glossopharyngeal nerve and synapses on Otic Ganglion –> Post-ganglionic synapses on parotid gland

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12
Q

Preganglionic sympathetic nerves originate at the ___, whose postganglionic fibers extend to the glands in the ____ spaces

A

cervical ganglion

Periarterial

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13
Q

What effect does conditioning, food, nausea, and smell have on parasympathetic innervation for salivary secretion?

What effect does fatigue, dehydration, fear, and sleep have on parasympathetic innervation for salivary secretion?

A

Stimulatory

Inhibitory

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14
Q

The blood supplied to the salivary glands is distributed by branches of the ____ artery

A

Branches of the external carotid

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15
Q

What are the main components of gastric juice?

A 
HCl (H+)
Pepsinogen
Mucus
IF
Water
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16
Q

___, together with pepsin, initiates the process of protein digestion and is necessary for the conversion of pepsinogen to pepsin

A

HCl (H+)

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17
Q

____, together with HCO3, neutralizes acid and maintains the surface of the mucosa at a neutral pH

A

Mucus

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18
Q

___ is required for the absorption of vitamin B12 in the ileum

A

Intrinsic Factor

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19
Q

The ____ gland is located in the proximal 80% of the stomach (body and fundus) and secretes acid

The ____ gland is located in the distal 20% of the stomach (antrum) and synthesizes and releases gastrin

A

Oxyntic

Pyloric

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20
Q

The result of the cellular mechanism by gastric parietal cells is net secretion of ___ and net absorption of ___

A

HCl

HCO3-

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21
Q

___ is released from ECL cells in the gastric mucosa and stimulates HCl secretion.

A

Histamine

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22
Q

Histamine binds to ___ receptors on parietal cells and its action can be blocked by this drug: ____

A

H2

Cimetidine

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23
Q

Binding of histamine to H2 receptors leads to a 2nd messenger cascade via ___ that ultimately results in secretion of H+ through _____ ATPase

A

Cyclic AMP

H+/K+

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24
Q

___ is released from the vagus nerve innervating the gastric mucosa and stimulates HCl secretion.

A

Ach

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25
Q

Ach binds to ___ receptors leading to this ____ 2nd messenger cascade that ultimately results in secretion of H+ via the ____ ATPase

A

M3 mAChRs

IP3/Ca2+

H+/K+

26
Q

Ach can have an indirect effect on HCl secretion through stimulation of ___ Cells, which release histamine

A

ECL

27
Q

___ is secreted into circulation by G cells in the antrum and delivered back to the stomach via the circulation. It stimulates HCl secretion

A

Gastrin

28
Q

Gastrin binds to ____ receptors on parietal cells and binding to these receptors leads to this ___ second messenger cascade that ultimately results in the secretion of H+ through the ___ ATPase

A

CCKb

IP3/Ca2+

H+/K+

29
Q

___ is released from delta cells (mostly located in the antrum) and inhibit HCl secretion

A

Somatostatin

30
Q

Somatostatin binds to ___ receptors on parietal cells and binding results in inhibition of ____ that ultimately results in inhibition of secretion of H+ (direct pathway)

A

Somatostatin receptor type 2 (SSTR2)

Adenylate cyclase

31
Q

In the indirect pathway, somatostatin inhibits ____

A

Both histamine release from ECL cells and gastrin release from G cells

32
Q

___ can potentiate the actions of Ach and Gastrin

___ can potentiate the actions of histamine and gastrin

A

Histamine

Ach

33
Q

What drug is an antagonist of H2 receptors that blocks that action of histamine and potentiated effects of Ach and gastrin?

What drug is an antagonist of mAChR’s that blocks the direct effects of Ach and Ach-potentiated effects of histamine and gastrin?

A

Cimetidine

Atropine

34
Q

___ inhibits the H+/K+ ATPase on gastric parietal cells and is used to treat ulcers to reduce H+ secretion

A

Omeprazole

35
Q

List the 3 phases of Gastric HCl secretion

A

Cephalic (30%)
Gastric (60%)
Intestinal (10%)

36
Q

List the 2 mechanims of the cephalic phase of gastric HCl secretion

A

Vagus n. –> Parietal cell: innervation releasing Ach to parietal cells, Ach stimulates secretion of HCl from parietal cells

Vagus n. –> gastrin –> parietal cell: innervation releasing Gastrin-releasing peptide (GRP) to G cells, G cells release gastrin into circulation, gastrin is delivered back to stomach to stimulate HCl secretion from parietal cells (VAGOTOMY ABOLISHES THIS PHASE)

37
Q

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

A

Distention of stomach and presence of breakdown of proteins, AAs, and small peptides

Distention activates mechanoreceptors in the mucosa of both oxyntic and pyloric glands

38
Q

Describe the mechanism of Distention of Antrum of the Gastric phase of Gastric HCl secretion

A

Distention of antrum –> local reflex (pyloropyloric reflex) –> gastrin –> parietal cells –> HCl

39
Q

At low secretion rates, final gastric juice is essentially a solution of ____

At higher secretion rates, the concentration of Na+ ___ and that of H+ ____

At peak rates, gastric juice is primarily ____

A

NaCl

decreases, increases

HCl

40
Q

Regarding gastric juice, the concentration of H, K, Cl are ___ than those in plasma, and the concentration of Na is ___ than that in plasma

A

Higher

Lower

41
Q

Non-parietal gastric juice secretions have a basal ___ secretion of constant and low volume and its primary constituents are ____

A

Alkaline

Na and Cl; K is present at the same concentration as in plasma

42
Q

Parietal gastric juice secretion is slightly ___-osmotic and ___ is the only anion present

A

Hyper

Cl

43
Q

Regarding the regulation of gastrin release, ___ stimulates gastrin release while ___ acts on G cells to inhibit gastrin release

A

GRP

Somatostatin

44
Q

Vagal activation stimulates gastrin release by releasing ___ and inhibiting release of ___

A

GRP

Somatostatin

45
Q

How is gastrin regulated/inhibited?

A

Negative feedback regulation by gastrin (gastrin itself increases somatostatin)
H+ in the lumen of the stomach stimulate release of somatostatin

46
Q

___ is secreted by chief and mucus cells in the oxyntic glands and ____ stimulation is the most important stimulus for its secretion

A

Pepsinogen

Vagus nerve

47
Q

In order for pepsinogen to be converted to pepsin, what is required?

A

H+ secretion from parietal cells to lower pH of gastric contents (pH H+ triggers local cholinergic reflexes that stimulate chief cells to secrete pepsinogen

48
Q

What is the optimal pH range of pepsin? When is it reversibly inactivated? When is it irreversibly inactivated?

A

Optimal=1.8-3.5

Reversibly inactivated= >5.0

Irreversibly inactivated= >7-8

49
Q

Failure of Parietal cells to secrete IF may lead to ___

A

Pernicious anemia

50
Q

List protective components of gastric mucosa

List damaging components to gastric mucosa

A

Protective=HCO3, mucus, PG’s, mucosal blood flow, and growth factors

Damaging=Acid, pepsin, NSAIDs, H pylori, aspirin, alcohol, bile, and stress

51
Q

___ forms primarily because the mucosal barrier is defective and the major causative agent is H pylori

A diagnostic test of this peptic ulcer disease is based on __ activity

A

Gastric ulcers

Urease

52
Q

___ forms because H+ secretory rates are higher than normal and role of H pylori is indirect

A

Duodenal ulcers

53
Q

Zollinger-Ellison syndrome is associated with ___ ulcers. It is usually a tumor in the pancreas that secretes large quantities of ___

A

Duodenal

Gastrin

54
Q

What are the 2 main components of the exocrine pancreas secretion?

A

Aqueous solution containing HCO3

Enzymatic secretion

55
Q

___ activity stimulates pancreatic secretion and ____ activity inhibits pancreatic secretion

A

Parasympathetic

Sympathetic

56
Q

Pancreatic amylases and lipases are secreted as ___ enzymes by acinar cells and pancreatic proteases are secreted in inactive forms and converted to their active forms in the ___

A

Active

lumen of the duodenum

57
Q

____ cells produce the initial aqueous solution from the pancreatic secretions which is isotonic and contains Na, K, Cl, and HCO3. The initial secretion is then modified by transport processes in the ____ cells

A

Centroacinar and ductal

Ductal epithelial

58
Q

After modification of initial pancreatic secretion by ductal cells, the net result is secretion of ___ into the pancreatic ductal juice and net absorption of ___

A

HCO3

H+

59
Q

At increased flow rate, what are concentration of HCO3 and Cl in the pancreatic juice?

At decreased flow rate, what concentrations of HCO3 and Cl in the pancreatic juice?

A

HCO3=highest, Cl=lowest

HCO3=lowest, Cl=highest

60
Q

Which phase of pancreatic secretion accounts for 80% of pancreatic secretion and is regarded as the most important phase?

A

Intestinal-Both enzymatic and aqueous secretions are stimulated

GI-Final (9 decks)

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