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PHYSIOLOGY III > L20: Secretions from Salivary glands and stomach > Flashcards

L20: Secretions from Salivary glands and stomach Flashcards

1
Q

what is the cephalic phase of secretion

A

the anticipation of food triggers autonomic and endocrine reflexes (increased saliva, gastric acid, gastrin and pancreatic enzymes) that prepare the GI tract

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2
Q

what are the 3 phases of secretions from salivary glands and the stomach

A
  1. cephalic: food anticipation
  2. gastric: mechanical stimulation of oral cavity + stomach
  3. intestinal phase: regulation of stomach emptying and digestion/abs in SI
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3
Q

at which secretory phase does 70% of HCl secretion in the stomach occur

A

gastric

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4
Q

what are the 4 salivary glands

A

parotid
mandibular
lingual
buccal

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5
Q

what is the composition and functionof saliva

A

composition: water, electrolytes, salivary proteins, urea (ruminants)
function: solvent for molecules to stimulate taste buds, food lubricant, keeps mouth clean, contains buffer, lysozymes and antitoxic proteins

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6
Q

what are lysozymes

A

antibacterial proteins that break down bacterial cell walls

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7
Q

salivary glands are ______ glands

A

acinar

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8
Q

what do salivary glands consist of

A

collecting ducts and acini
acini are the secretory unit

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9
Q

secretory unit of salivary glands are called ______ and they empty into ______

A

acini
collecting ducts

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10
Q

what is ptyalin (alpha amylase)

A

salivary enzyme for digestion of starches

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11
Q

what is the pH of saliva

A

6-7, ideal pH for activity of alpha amylase (ptyalin)

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12
Q

what is mucin

A

lubricant that facilitates swallowing and protects buccal surfaces

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13
Q

what ions are removed (reabsorbed) from saliva, what are added in (secreted)

A

Na and Cl are removed; K+ and bicarbonate are added

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14
Q

what is a salivary mucocele (sialocele)

A

painless swealling of neck or within oral cavity caused by a collection of saliva that leaked from a damaged salivary gland or duct and has accumulated in interstitial tissues

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15
Q

saliva osmolarity is determined by ______; saliva is hypotonic at ______ and close to isotonic at ______

A

flow rate
hypotonic - slow flow rates
isotonic - high flow rates

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16
Q

how does flow rate determine saliva osmolartity

A

at high flow rates, saliva is nearly isotonic due to less time for the modification of ions in the ducts (less removal of Na, Cl)
compared to at slow flow rates there is more time for removal of Na and Cl

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17
Q

what restricts osmotic reabsorption of water in acinar cells

A

tight junctions

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18
Q

salivary duct cells reabsorb ____ and _____ in exchange for H+ and HCO3

A

Na and Cl

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19
Q

is salivary protein concentration affected by flow rate

A

no

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20
Q

the parotid salivary glands consist of _____ cells, providing ______ to saliva

A

serous
proteins

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21
Q

the sublingual and submandibular salivary glands consist of a mixture of ____ and _____ cells

A

mucus (more glycoproteins) and serous cells

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22
Q

enzyme that initiates starch digestion in pigs and humans but not in carnivores or horses

A

alpha amylase (ptyaline)

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23
Q

what is lingual lipase

A

enzyme in young animals on a milk diet; initiates hydrolysis of triglycerides into diacylglyceride and a free fatty acid

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24
Q

in ruminants and other herbivores, saliva contains lysozymes and ______ proteins

A

antitoxic

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25
Q

what is tannin, how can saliva protect against it

A

plant defense mechainism - polyphenolic compounds in plants that have a bitter taste and negatively affect digestion in SI

some saliva have proteins that have antitoxic effects against phenolic compounds

26
Q

_____ glands produce proline rich proteins which binds and neutralize tannin

A

parotid

27
Q

do browsers or grazers have larger parotid glands and why

A

browsers (eat shrubs, leaves, bark, etc contain lots of tannnins) have larger parotid glands since they eat plants with higher tannin concentrations

28
Q

what is the main purpose of saliva in ruminants

A

it is a buffer (pH 8) for VFAs which are constantly being produced by microbial activity

29
Q

4 main components of gastric juice

A

HCl
pepsiongen
mucus
intrinsic factor

30
Q

what does HCl do

A
  • decreases pH of stomach
  • activates pepsinogen
  • aids in protein digestion
  • kills bacteira
31
Q

what does pepsinogen do

A

pepsin (active form) digests proteins

32
Q

what is the purpose of mucus

A

protects gastric mucosa from corrosive actions of HCl

33
Q

what is the purpose of intrinsic factor

A

needed for the absorption of vit B12 in ileum

34
Q

the epithelium in the glandular region of the stomach contain what cell types

A
  • chief
  • parietal
  • enteroendocrine
35
Q

chief cells do what

A

convert pepsinogen into pepsin

36
Q

what cells secrete HCl

A

parietal

37
Q

what cells produce a substance with a protective function against acid and mechanical damage of the stomach

A

surface mucous cells

38
Q

what are the stem cells of the stomach

A

mucus neck cells - thin mucus and are progenitor cells (stem)

39
Q

what are the enteroendocrine cells of the stomach that produce hormones that regulate gastric secretion and motility

A

D-cells, G-cells, ECL cells

40
Q

where is HCl formed and what does it require

A

gastric lumen by parietal cells, requires ATP

41
Q

Cl is exchanged from bicarb producing an _______

A

alkaline tide
temporary increase in blood pH

42
Q

what catalyzes bicarbonate formation from OH and CO2

A

carboanhydrase

43
Q

when does an alkaline tide occur

A

after a meal

44
Q

what are the functions of HCl

A
  • activates pepsinogen
  • aids in breakdown of CT and proteins
  • kills microorganisms
45
Q

what is the neural control of HCl secretion

A

PNS and ENS activate parietal cells via M3 receptors (activated by ACh via the cholinergic system)

46
Q

what is the endocrine control of HCl secretion

A

secretions of gastrin from G-cells; gastrin binds to CCK-B receptors
secretion of histamine from ECL binds to H2 receptors

47
Q

what is histamine released in response to

A

gastrin

48
Q

what is gastrin released in response to

A
  • small peptides in AA and stomach
  • distension of stomach
  • vagal stimulation
49
Q

what are the intracellular mechanisms that mediate the activation of the H+/K+ ATPase

A
  • the PNS (ACh) and gastrin through GPCRs that stimulate IP3/DAG which increase Ca+ concentration
  • by histamine receptors mediating an elevation of cAMP concentration
  • both Ca and cAMP stimulate the proton pump
50
Q

what is the main source of histamine in the stomach

A

ECL cells (enterochromaffin-like)

51
Q

what inhibits histamine and gastrin release in the stomach

A

somatostatin released locally (paracrine)

52
Q

what cells are measuring the pH of the stomach and what pH triggers a negative feedback

A

G-cells
pH < 2

53
Q

what things cause a downregulation of HCl production

A
  • absence of food
  • somatostatin and prostaglandin
54
Q

what are the components of the gastric mucosal barrier

A
  • compact epithelial cell lining
  • gastric mucus covering
  • bicarbonate secreted by surface epithelial cells
55
Q

what is the purpose of the gastric mucosal barrier and what are the consquences of it being broken

A
  • helps protect stomach epithelial lining against the acidic environment
  • if barrier is broken, acid can diffuse across mucosa and damage the stomcah wall
56
Q

what is a gastric ulcer and what can cause it

A

localized area of erosion of the mucosal layer
caused by: defect in mucosal barrier, hypersecretion of HCl and H.pylori

57
Q

what are the therapeutic approaches for treating a gastric ulcer

A
  • reduced acid production (vagotomy or proton pump inhibitor)
  • stimulate re-epithelization
  • H.pylori antiiotics
58
Q

where are proenzyme pepsinogen stored

A

zymogen granules; are released by exocytosis upons stimulus

59
Q

what is the function of pepsin

A

cleaves proteins to peptides at aromatic links

60
Q

what things stimulate pepsinogen

A
  • PNS (vagus n) acts on chief cells
  • gastric acts on chief cells
  • secretin from the duodenum stimulate chief cells

PHYSIOLOGY III (31 decks)

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