salivary, gastric and pancreatic secretions

Question 1

what stimulation causes watery saliva

Answer 1

cholinergic (parasympathetic, ACh)
adrenrgic (symp +NA)
peptidergic

Question 2

what nerve is the parasympathetic enervation os salivation through and what does it cause

Answer 2

chorda lingual nerve

fluid secretion, increased blood flow and oxygen consumption

Question 3

what is salivary fluid secretion (but not blood flow) blocked by

Answer 3

atropine (possibly VIP or substance P co-release)

Question 4

what does sympathetic stimulation cause

Answer 4

initial vasoconstriction then vasocilation

viscous, protein rich secretion by B-adenergic (less salivation)

Question 5

how is glandular tissue organised

Answer 5

acinar cells surrounding small central lumen

Question 6

what are the 2 main stages of saliva formation

Answer 6

1. isotonic primary fluid (plasma-like electrolyte comp) formed by acinar cells (primary saliva)
2. modified in duct system by reabsorption of NaCl and secretion of K and HCO3

Question 7

Maximum rate of saliva flow in humans

Answer 7

1 ml/min.g.

Question 8

what are acinar cells

Answer 8

• exocrine cells of pancreas
• produce and trans digestive enzymes to duodenum
• water/protein secretion via vesicular and granular pathways
• primary secretion

Question 9

what happens to saliva as it moves down the duct (strip/interlobular segment)

Answer 9

Na pumped out into interstitial = hypotonic saliva
K enters
H leaves
HCO3 enters

Question 10

what are duct cells’ function

Answer 10

modifications of saliva—secondary secretion

Question 11

production of saliva is NOT due to hydrostatic pressure, it is due to..

Answer 11

ionic pump involving processes and movement of water

Question 12

what are the roles of acinat and ductal cells in salivary secretion

Answer 12

• secrete proteins and electrolytes into oral cavity
• lubricate - swallow
• starch digestion: glycoproteins and amylase
• highly fenestrated vasculature to guarantee sufficient nuteirts and water

Question 13

what are the main glands involved in salivary secretion

Answer 13

parotid - stim by taste and touch

sublingual and submandibular glands

Question 14

what are the transmission mechanisms that the salivary centre stimualtes

Answer 14

• adrenergic (sympathetic)
• NANC (VIP)
• cholinergic (parasymp. inc blood flow by dilating)

Question 15

what does the parasympathetic nerve innervate (receptors and substrates)

Answer 15

VI –> VIP receptor –> NO and cAMP

ACh –> M1,3 receptor –> Ca

Question 16

how much can blood flow increase by if stimulated for saliva

Answer 16

5-10 fold

Question 17

what is the end effect when salivary centre is stimulated

Answer 17

• contract myoepithelial cells around salivary duct
• dilate blood vessels
• IgA secretion -plasma cells

Question 18

(describe the sympathetic nerve pathway for salivation )

Answer 18

• release NA
• act on B1 and a1 receptors
• B1 modulate cAMP and NO levels
• a1 modulates Ca levels

Question 19

(describe the parasympathetic pathway for salvation )

Answer 19

• release VIP –> VIP receptor which modulates cAMP and nO)
• ACh - M1,3 receptors - modulate Ca
• interplay between cAMP and Ca = water/protein balance

Question 20

what are some physiological changes at old age contributing to hypo-salivation

Answer 20

• gland atrophy –>
• salivary gland hypofunciton –>
• salivary secretion decreases

Question 21

what do chief cells secrete

Answer 21

pepsinogen - start protein digestion

Question 22

what do parietal cells secrete

Answer 22

HCl

Question 23

what cell type lines glandular stomach, gastric pits and tubular invaginations

Answer 23

columnar epithelium of surface mucosa cells

Question 24

explain funcitonal adaptations of stomach epithelium during HCl secretion

Answer 24

• musous lining - protect and buffer by releasing HCO3
• intrinsic factor (a glycoprotein) - combine w vit B12 - aid absorption in ileum
• secretions include pepsin - protein digest

Question 25

what stimulates HCl secretion

Answer 25

ACh histamine gastrin

Question 26

what are the phases of gastric acid secretion

Answer 26

basal and stimulated--> cephalic gastric intestinal

Question 27

describe propulsion, grinding and retropulsion

Answer 27

1. bolus towards closed pylorus by peristalsis 2. antrum churns trapped material 3. most bolus pushed back to stomach

Question 28

how does the high fenestrated endothelium help nutrient supply and buffering

Answer 28

- parietal secretes H (into gastric pit) and HCO3 which enters capillaries - arteroiles vasodilator due to NO and PGI2 to increase blood flow here - blood carries HCO3 to mucus barrier

Question 29

what happens when partial cells are activated

Answer 29

tubulovesicles become intracellular caniculi - secrete more H

Question 30

what does the mechanism of H+ secretion against enormous gradient require?

Answer 30

- energy generated by oxyntic glands by aerobic resp - luminal H:K:ATPase - pump H to stomach lumen - high gradient in canaliculi

Question 31

what's Soll's three receptor modle

Answer 31

gastrin - CCK2 histamine - H2 ACh- M3 all secrte HCL

Question 32

what's dimaline model

Answer 32

CCK2 and M3 on enterocytes- weak action | gastrin - CCK2 - ECL cell- histamine - binds to H2. Main secretion of HCL

Question 33

what are the two ways to inhibit further action of D cells and inhibitn of acid secretion

Answer 33

1. H2 antagonist e.g. famotidine | 2. proton pump inhibitor e.g. omeprazole

Question 34

what does somatostatin do and what is it released by

Answer 34

inhibit gastrin release by G cell | released by D cell

Question 35

what does gastrin releasing peptide (GRP) do

Answer 35

stimulate more gastrin release byG cells

Question 36

briefly describe the action of omeprazole

Answer 36

-selectively block proton pump - doesnt completely stop acid secretion (to continue digestion of food)

Question 37

what condition is omeprazole used for

Answer 37

peptic ulcer and reflux oesophagitis

Question 38

how does fat affect aid secretion

Answer 38

more fat = less acid secretion | fat requires bile salts from the liver

Question 39

what organ has the highest rate of protein synthesis

Answer 39

pancreas (exception of lactating mammary gland)

Question 40

what proteolytic enzymes are released by the pancreas

Answer 40

``` trypsinogen chymotrypsinogen procarboxypolypeptidase ribonuclease deoxyribonuclease ```

Question 41

what enzymes (exp. proteolytic) are secreted by pancraese

Answer 41

amylase - starch and glycogen | lipase - fat into glycerol and FA

Question 42

what transporters are involved in pancreatic HCO3 secretion

Answer 42

NA:K-ATPase Na:2Cl:K triporter Na channel Cl channel (lumina surface)

Question 43

what does protein ad fat digestion in the duodenum lead to

Answer 43

CCK secretion | acinar cells release proenzymes

Question 44

what does low pH in duodenum cause

Answer 44

HCO3 secretion