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MONOGASTRIC GI > 5.1a – Salvia and Gastric Secretions I > Flashcards

5.1a – Salvia and Gastric Secretions I Flashcards

1
Q

Where are secretory cells found?

A

-lower parts of crypts and submucosal glands along the GI
-salivary glands
-pancreas
-airways
-most mucus membranes

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2
Q

What does secretory diarrhea do to the secretory cells?

A

-over-activates them
>get excessive ion secretion=pulls water into GIT=diarrhea

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3
Q

What drives the secretory cell process?

A

-3Na/2K ATPase
>creates charge separation and concentration differences
*energy is required because you are moving Na/K against their concentration gradients

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4
Q

What happens when secretory cell is activated?

A

-increase either Ca2+ and/or cAMP

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5
Q

What does the increase in Ca2+ and/or cAMP activate?

A

-Cl- channels and/or
>Ca2+ activated Cl- channel
>cystic fibrosis transmembrane regulator (CFTR)
*via NTs from the ENS (ex. VIP, ACh)

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6
Q

K+ channel activation via Ca+ and/or cAMP leads to:

A

-further hyperpolarization of the membrane
>increases force for driving Cl- out of the cell

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7
Q

What is done to maintain electroneutrality with the increase in Ca+ and/or cAMP?

A

-Cl- and/or bicarbonate move out of the cell into the lumen
>pulls Na paracellularly through the incomplete tight junctions

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8
Q

What helps to replenish the Cl- in the cell?

A

-NKCC

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9
Q

What helps replenish bicarbonate?

A

-carbonic anhydrase
-proton exit the basolateral side of the cell through a cation exchanger

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10
Q

What creates the osmotic drive for water to move?

A

-the movement of ion (Na and Cl) either paracellularly (via aquaporins) OR through gap junctions

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11
Q

What are the 3 glands that produce saliva?

A

-parotid
-mandibular (submaxillary)
-sublingual

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12
Q

What are the cells that produce saliva?

A

-acinar cells
>water secretion to more mucous (species and GIT site differences)
*innervated by PS pathways

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13
Q

What happens to saliva when secretin is secreted by the duodenum in response to low ph?

A

-alkalinity is increased

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14
Q

What are the functions of saliva?

A

-facilitate mastication and swallowing
-dilution and cleaning of oral cavity
-buffering
-protection of tooth enamel
-absorption of Vit B12
-antibacterial
-cooling (ex. cat and dog)

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15
Q

Saliva and the absorption of Vit B12:

A

-produces a glycoprotein that binds B12
>protects it from the stomach acidity
>released in duodenum so B12 can be absorbed

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16
Q

Cooling via saliva in a dog:

A

-can produce 10x more saliva than a human when hot

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17
Q

Cat grooming:

A

-use hollow papillae to wick salvia into fur
-tongue separates the fur exposing the skin=evaporation causes a temperature drop

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18
Q

Salivary gland ‘pathway’:

A

-secretions from acinar cells are connected by a series of ducts
-converge into an intercalated duct
-drains into excretory ducts
-converges into a main duct
*2 stage model

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19
Q

Composition of the main ions in saliva change as the:

A

-flow rate is increased

20
Q

What is the basal (unstimulated) secretion from the submaxillary and parotid of non ruminants?

A

-hypotonic
*as flow increases, Na, Cl, and HCO3 increase at maximal flow rates=becomes isotonic

21
Q

Ruminant saliva at any rate is:

A

-isotonic

22
Q

Saliva vs. plasma:

A

-saliva at all flow rates hypotonic to plasma
-HCO3- in saliva is higher than plasma except at very low rates

23
Q

What else can saliva contain?

A

-alpha-amylase (except carnivores and ruminants)
-small amounts of lipase
-lysozymes (antibacterial)

24
Q

What are the ionic composition differences in saliva in different species at maximal flow?

A

*ruminants have higher HCO3- and K+, makes it more alkaline

25
Q

What are the ionic composition differences in saliva in parotid and submandibular gland in ruminants at maximal flow?

A

-Na+ and HCO3- are much higher in the parotid gland

26
Q

Primary secretion of saliva contains:

A

-amylase and electrolytes produced in the acinar cell
-concentrations of electrolytes is comparable to plasma

27
Q

Modification of primary salvia as it passes through ducts:

A

-Na and Cl are absorbed
-K and HCO3 are secreted
*pH will increase before salvia is released

28
Q

What are the 4 secretory areas of the stomach?

A

-esophageal stomach
-cardia
-fundic
-pyloric

29
Q

Esophageal stomach:

A

-lined by stratified squamous epithelium
-no mucus, acid or enzymes produced
-very large in dog, pig and cow

30
Q

Cardia:

A

-glandular
-invaginations in the submucosa forming short glands
-lined by simple columnar cells that produce thick mucus and buffer
-very large in pig
-small in dog
-absent in cow

31
Q

Fundic:

A

-‘stomach’
-deep invaginations in the submucosa
-lined by cells that produce ACID, proteolytic enzymes, hormones and mucus
-seen in all mammals

32
Q

Pyloric stomach:

A

-moderately deep glands
-lined by epithelial cells that produce mucus and buffers, not acid or enzymes
-enteroendocrine cells (G cells that produce gastrin in response to distension or increased pH)
-sphincter at end

33
Q

Parietal glands contain a variety of cell types including:

A

-parietal cells
-chief cells
-endocrine cells
-D cells
-mucus cells
-mucus neck cells

34
Q

The antral mucosa of parietal glands have NO:

A

-chief cells
-parietal cells

35
Q

Endocrine cells in parietal glands synthesize:

A

-histamine via histidine decarboxylase

36
Q

D cells in parietal glands:

A

-found close to parietal cells
-secrete somatostatin

37
Q

Mucous cells in parietal glands:

A

-found on top of gland
-join with the gastric pit

38
Q

Mucus neck cells in parietal glands are the:

A

-precursors for all other functional cell types

39
Q

Parietal cells:

A

-elaborate system of intracellular membrane
-large numbers of mitochondria
*secrete HCL against a concentration gradient 2.5million fold

40
Q

What happens to the apical membrane of parietal cells during secretion?

A

-amplified by fusion of the microvesicles and secretory canaliculi
>accompanied by increased density of H+, K+ and ATPase molecules

41
Q

What do ACh and gastrin use to signal?

A

-Ca2+

42
Q

What does histamine use to signal?

A

-cAMP

43
Q

What is needed to pump H+ into the lumen of canaliculus?

A

-energy

44
Q

What are the steps of gastric secretion from the parietal cells?

A
  1. Cl actively transported from parietal cell to lumen of canaliculus
  2. Na actively transported out of canaliculus
  3. Water becomes dissociated into H+ and OH- (b/c weak acid)
  4. H+ secreted into canaliculus in exchange for K+
  5. CO2 (from metabolism or blood) combines due to carbonic anhydrase with OH to form HCO3-
  6. HCO3- diffuses out of parietal cell into ECF in exchange for Cl-
45
Q

What controls the gastric secretion form parietal cells?

A
  1. H+/K+ ATPase (depends on the K+ going out)
  2. Inhibited by omeprazole
    *[HCl] drives water into gastric contents to maintain osmolarity
    *Amount of HCO3- in blood = amount of HCl secreted
46
Q

Omeprazole:

A

-proton pump inhibitor (H+/K+ ATPase)
-used to treat frequent heart burn
-used for dogs and cats

47
Q

What does ‘alkaline tide’ refer to?

A

-temporary increase in blood pH following a meal

MONOGASTRIC GI (24 decks)

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