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Gastrointestinal Physiology: Secretion I Flashcards

1
Q

The largest contributor to GI secretion

-Secreted in the upper portion of the GI tract and reabsorbed in the lower portion

A

Water

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2
Q

Serves a protective function for the epithelial surface all along the tract

A

Mucus

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3
Q

In general, are secreted via 2nd messenger activated fusion of granules with the luminal membrane

A

Enzymes

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4
Q

Initiated by active transport, primary or secondary, of one ion through the basolateral membrane and diffusion through the apical membrane or by active transport of one ion through the apical membrane

A

Electrolyte secretion

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5
Q

The composition of saliva varies. But what are the two constants?

A
  1. ) Always hypotonic

2. ) K+ is higher than in plasma

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6
Q

Saliva secretion declines with age. In children, we see an average saliva secretion of

A

1-1.5L per day

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7
Q

The resting secretory rate for saliva is

A

25uL/min

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8
Q

Concentration of electrolytes in saliva varies, but it is always

A

Hypotonic

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9
Q

Relative to serum, saliva is always lower in concentration of

A

Na+ and Cl-

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10
Q

Most of the time, saliva is rich in

A

HCO3-

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11
Q

In the two-stage secretion model for saliva, primary secretions are performed by the

A

Acinar cells

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12
Q

In the two-stage secretion model for saliva, primary secretions by the acinar cells is followed by modifications of the luminal fluid by the

A

Ductal Cells

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13
Q

An isotonic ultrafiltrate of plasma that is secreted by the acinar cells

A

Primary secretion

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14
Q

Modify the primary secretion fluid by reabsorbing Na+ and Cl- and secreting K+ and HCO3-

A

Ductular epithelial cells

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15
Q

Here, there is a greater amount of Na+

and Cl- reabsorbed than

A

K+ and HCO3- secretion

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16
Q

This reduction in the number of ions in the tubular fluid plus the impermeability of ducts leads to a

A

Hypotonic Saliva

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17
Q

What two things increase during active saliva secretion?

A

Metabolic hyperemia and vasodilation

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18
Q

Due to a local increase in the concentrations of metabolic end products

A

Metabolic hyperemia

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19
Q

Mediated by vasoactive intestinal polypeptide (VIP) from non-cholinergic parasympathetic fibers and by bradykinin

A

Vasodilation

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20
Q

Higher in Cl- and K+ than plasma, and much higher in H+

A

Gastric Juice

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21
Q

Whatis the approximate amount of gastric juice secreted per day?

A

2L

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22
Q

Continued loss of saliva and gastric juice (vomiting or aspiration) can lead to water and electrolyte losses that result in

A

Dehydration, metabolic alkalosis, and severe electrolyte imbalance

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23
Q

Functions to liquify the bolus and form chyme

A

Gastric secretions

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24
Q

Gastric secretions provide intrinsic factor for absorption of

A

Vitamin B12

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25
Q

Stabilize an absorbable form of some minerals (Ca+2, Fe+2)

A

Gastric Secretions

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26
Q

Surface columnar mucous and epithelial cells secrete mucus and an

A

Alkaline fluid

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27
Q

Fundic glands (straight) have which three types of cells?

A
  1. ) Chief cells
  2. ) Parietal cells
  3. ) Neck Chief Cells
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28
Q

Secrete pepsinogens

A

Chief cells

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29
Q

Secrete HCl and IF (oxyntic)

A

Parietal cells

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30
Q

Secrete mucus & are the progenitors of luminal cells

A

Neck Chief Cells

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31
Q

Pyloric glands (branched) have which two secretory cell types?

A

Mucous cells and G cells

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32
Q

Secrete mucous and pepsinogens

A

Mucous cells

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33
Q

Release gastrin into the blood (not lumen)

A

G cells

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34
Q

States that there are two different secretions from different cells with different controls

A

Two component hypothesis

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35
Q

What are the two components of the two component hypothesis?

A
  1. ) Oxyntic component (isotonic HCl)

2. ) Non-oxyntic component (mucosal barrier)

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36
Q

Transported into the lumen in the resting oxyntic cell and the surface epithelial cell

A

Cl-

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37
Q

This movement is by HCO3-/Cl exchangers in the basolateral membrane and Cl channels in the

A

Luminal Membrane

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38
Q

A major contributor to the negative electrical potential difference (-70 to -80 mV) between the stomach lumen and blood (lumen negative)

A

Oxyntic component

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39
Q

Upon stimulation, oxyntic cells undergo structural changes and actively secrete which two things?

A
  1. ) Isotonic HCl into lumen

2. ) HCO3- into interstitial area

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40
Q

At the whole body level, stimulation of acid secretion is normally associated with

A

Meals

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41
Q

Inhibition of acid secretion is associated with loss of stimuli + specific inhibition of

42
Q

Paracellular movement and cellular secretion of an isotonic ultrafiltrate of plasma that is high in K+ (10-20 mM) and HCO3- (45 mM)

A

Non-oxyntic component

43
Q

In the non-oxyntic component, HCO3- is produced in the epithelial cells, and transported from the blood into the cell by a

A

Basolateral HCO3-

44
Q

This HCO3- is secreted at the luminal membrane by an electroneutral Cl/HCO3 exchanger, stimulated by

45
Q

This HCO3- is also secreted at the luminal membrane by an electrogenic HCO3 transporter, stimulated by

A

Prostaglandin E2

46
Q

In the non-oxyntic component, soluble mucus is released from the mucous neck cells in response to

A

PNS stimulation via ENS

47
Q

In the non-oxyntic component, visible mucus is released from the surface cells in response to

A

Mechanical irritation and chemical stimulation

48
Q

Local reflex, and both sympathetic and parasympathetic activity via the ENS play a minor role in

A

Visible mucous secretion

49
Q

The non-oxyntic component secretions create the mucosal barrier. This barrier can neutralize about

A

20 mM of acid

50
Q

Cytoprotection of gastric, small intestinal, liver and pancreatic cells has been experimentally observed with

A

Prostaglandins E2, F2, I2, and alpha

51
Q

Effective concentrations of the prostaglandins are below those that inhibit acid secretion in the

A

Oxyntic cells

52
Q

Five common agents known to cause disruption of the gastric mucosal barrier and epithelial cell destruction are?

A
  1. ) Aspirin
  2. ) Nonsteroid anti-inflammatory agents
  3. ) Ethanol
  4. ) Bile acids
  5. ) H. Pylori
53
Q

Causes intracellular acidification and inhibits prostaglandin synthesis, and the secretion of mucus and HCO3-

54
Q

Inhibit prostaglandin synthesis, and mucus and HCO3- secretion

A

Nonsteroidal Anti-Inflammatory Drugs (NSAIDS)

55
Q

Inhibits intracellular enzymes

56
Q

Solubilizes the plasma membrane

A

Bile acids

57
Q

Induces inflammation and an immune response through production of NH4+ and other virulence factors

58
Q

Secreted by oxyntic cells

-The control appears similar to acid secretion

A

Intrinsic factor

59
Q

Secreted by chief and mucous cells

-secretion is correlated with acid secretion

A

Pepsinogen

60
Q

The common secretogues of pepsinogen are

A

ACh and Secretin

61
Q

Secretion of pepsinogen is potentiated by luminal acid via a

A

Local reflux

62
Q

The composition of pancreatic juice depends on the number and type of secreting cells, and the

A

Secretory rate

63
Q

Up to 2 L of pancreatic juices are secreted daily, mostly in response to

64
Q

Has essentially no pancreatic amylase activity, negligible lipase activity, low protease activity, and the pancreas does not respond to CCK stimulation

65
Q

Lipases from milk, lingual and gastric sources and salivary amylase play an important role in

A

Infant digestion

66
Q

Normal pancreatic function develops by age

67
Q

Functions to provide enzymes for intraluminal digestion of most foods. protect the mucosa and provide an alkaline environment for optimal enzymatic activity

68
Q

Secrete proteins via fusion of zymogen granules with the apical membrane

A

Acinar cells

69
Q

Acinar cells also secrete a small amount of fluid that is essentially

A

Isotonic HCl

70
Q

Secrete a large volume of alkaline fluid, pH 7.6 - 8.2, that is high in HCO3-

A

Pancreatic extralobular ductule cells

71
Q

The proposed fluid secretion mechanism of the pancreas is the two component hypotheses, plus HCO3-/Cl exchange in the main collecting ducts that transports HCO3- in and Cl- out of the

A

Ductal cell

72
Q

With disfunctional CFTR, cystic fibrosis patients have insufficient

-at higher risk for pancreatitis

A

Pancreatic secretion

73
Q

During the interdigestive period, basal secretion from the pancreas accounts for what percentage of

  1. ) HCO3-
  2. ) Enzymes
A
  1. ) 2-3%

2. ) 10-15%

74
Q

Accounts for 10-15% of the volume & 25% of the enzymes released from the pancreas in response to a meal

A

Cephalic phase

75
Q

The cephalic phase is under what control?

76
Q

A continuation of the cephalic with greater neural stimulation due to gastric distention

A

Gastric phase of pancreatic secretion

77
Q

Accounts for 70-80% of a meal response (CCK, secretin & reflexes)

A

Intestinal phase of pancreatic secretion

78
Q

There is 500-1500 ml/day of an electrolyte solution coming from the small intestinal epithelial and

A

Crypt cells

79
Q

Functions to maintain isotonicity and fluidity of luminal contents, this aids absorption and protect the epithelial surface

A

Intestinal secretions

80
Q

In intestinal secretion, ion movement is initiated by active transport of Cl and/or HCO3-, and other ions and H2O follow via

A

Passive diffusion

81
Q

H2O also enters the intestinal lumen in response to an increase in the concentration of osmotically active particles produced by

A

Gastric emptying and digestion

82
Q

Cl- enters the intestinal lumen through

83
Q

Activate CFTR and induce diarrhea

A

Cholera toxin and other microbial products

84
Q

Protected from diarrheal pathogens due to their insufficiency in intestinal fluid secretion

A

Cystic fibrosis patients

85
Q

External fluid circuit concept of intestinal secretion is absorption at the tip of villi and secretion at the base or in

86
Q

Fluid reabsorption can be significantly upregulated by the addition of

A

Glucose and NaCl

87
Q

One way to treat people with severe diarrhea is administering

A

Glucose and NaCl

88
Q

Functions to emulsify fats and solubilize hydrophobic substances (cholesterol in the gallbladder and biliary tract, plus free fatty acids and fat soluble vitamins in the small intestine)

A

Hepatic Secretions (excretion)

89
Q

Augment pancreatic HCO3- secretions to maintain an alkaline pH in the luminal of the small intestine

A

Hepatic Secretions

90
Q

Excrete lipid soluble substances and heavy metals from the body

A

Hepatic secretions

91
Q

A mixture of two solutions, one from the hepatocyte (organic substances and an isotonic filtrate of plasma), and one from the epithelial cells in the ductules and ducts (HCO3- enriched fluid)

92
Q

Secrete organic substances

A

Hepatocytes

93
Q

Amphipathic molecules that form micelles

-secreted by hepatocytes

A

Bile Salts

94
Q

Secrete phospholipids (lecithin), cholesterol, bile pigments (bilirubin), miscellaneous proteins, inorganic ions (Na+, K+, Ca2+, Cl and heavy metals) and H2O

A

Hepatocytes

95
Q

Secretion of the organic component depends on the availability of

A

Bile acids (salts)

96
Q

Rates of hepatocyte organic compound secretion are high during the intestinal phase due to return of

A

Bile acids (salts)

97
Q

The transporters for hepatocyte secretion belong to the

A

ATP-Binding Cassette (ABC) family

98
Q

The hepatic ductal cells secrete alkaline fluid. What stimulates HCO3- secretion?

99
Q

Functions to reabsorb Na+, Cl, H2O, and HCO3- concentrates and acidifies the bile

A

Gall bladder

100
Q

Free Na+, and Cl and/or HCO3- are transported out of the lumen of the gall bladder and into the

A

Epithelial cells

GI (59 decks)

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