Gi Tract: Exocrine Glands

Front 1

what are the seven substances that exocrine glands or secretory cells of the GI tract secrete into the GI lumen?

Back 1

digestive enzymes, mucus, HCL, water, electrolytes, intrinsic factor and bile

Front 2

what two secretion sources excrete the most amount of substance daily? what is the amount?

Back 2

Gastric mucosa and pancreas. 2000 mls

Front 3

which secretion source excretes the least amount of substance daily? how much?

Back 3

Large intestine. 200 mls

Front 4

what are the three phases of GI secretion?

Back 4

cephalic, gastric and intestinal

Front 5

in what phase is food NOT in the GI tract?

Back 5

cephalic

Front 6

what reflex is associated with the cephalic phase?

Back 6

Pavlov's reflex

Front 7

what affect does parasympathetic simulation have on the rate of GI secretion?

Back 7

it increases it.

Front 8

what affect does sympathetic stimulation have on the rate of GI secretion? how does it do that?

Back 8

It has a dual effect: It may slightly increase secretion or it may decrease secretion if secretion is already increased by parasympathetic/hormonal stimulation. It is able to do that via vasoconstriction and reduction of blood supply.

Front 9

what are the GI hormones?

Back 9

gastrin, cck, secretin, GIP, and somatostatin

Front 10

how is GI secretion regulated in the cephalic phase?

Back 10

via unconditioned reflexes which are stimulated by food in the mouth and secrete saliva
also via conditioned reflexes (Pavlov's) in reaction to sight and smell.

Front 11

how is GI secretion regulated in the Gastric phase?

Back 11

via vagal reflexes (Ach --> muscarinic receptors), intrinsic neurons (VIP and GRP- gastrin releasing peptide) and histamine, somatostatin and gastrin.

Front 12

which one of the peptide hormones associated with the gastric phase is considered a multipotent inhibitor?

Back 12

somatostatin

Front 13

how is GI secretion regulated in the intestinal phase?

Back 13

CCK and GIP inhibit gastrin release from G-cells and acid secretion by parietal cells and secretin (from S-cells) inhibits gastrin-stimulated acid secretion. These stop gastrin from duodenal G-cells from increasing gastric secretion.

Front 14

what salivary gland(s) secretes only serous saliva?

Back 14

parotid

Front 15

what salivary gland(s) secrete both mucous and serous saliva?

Back 15

submandibular and sublingual

Front 16

which salivary gland(s) secretes only mucous saliva?

Back 16

buccal

Front 17

what two glands account for 90% of total secreted of salivary glands?

Back 17

parotid and mandibular.

Front 18

what are the five functions of saliva?

Back 18

lubrication, protection, hygiene, digestion and excretory

Front 19

what enzymatic component of saliva is a precursor for bradykinin, a strong vasodilator?

Back 19

kallikrein

Front 20

what are the three enzymes that are a part of the composition of saliva?

Back 20

ptyalin, lingual lipase, and kallikrein

Front 21

what Immunoglobulin is present in saliva?

Back 21

IgA

Front 22

Besides the main components of saliva (water, mucus, electrolytes), enzymes and immunoglobulins, what three categories of substances does saliva contain?

Back 22

bactericidal (lysozyme, lactoferrin), blood group antigens, and sex steroids (testosterone, estrogen and progesterone)

Front 23

In regards to neutral pH, is the initial saliva hypertonic, isotonic, or hypotonic?

Back 23

isotonic

Front 24

before entering the oral cavity, in regards to neutral pH, does the saliva become hypertonic, isotonic or hypotonic? why?

Back 24

hypotonic; due to electrolyte modifications

Front 25

along the striated duct that will produce saliva, two molecules are secreted and three molecules are reabsorbed. what are they?

Back 25

secreted: HCO3 and K
reabsorbed: Na, Cl, and water

Front 26

what affect does parasympathetic stimulation have on the regulation of salivary secretion? sympathetic?

Back 26

they both increase.

Front 27

which stimulation is dominant, parasympathetic or sympathetic?

Back 27

parasympathetic

Front 28

Via what mechanisms does Parasympathetic stimulation affect salivation rate?

Back 28

via increased acinar and duct cell secretory activity and vasodilation

Front 29

what type of salivary secretion is secreted by the Parasympathetic Nervous system?

Back 29

copious, watery secretion

Front 30

what type of salivary secretion is secreted by the SNS (sympathetics)?

Back 30

thick, viscous secretion

Front 31

via what mechanisms does sympathetic stimulation affect salivation rate?

Back 31

via stimulation of myoepithelial cell contraction and causes vasoconstriction.

Front 32

Aldosterone causes an increase in secretion of _____ and an increase in reabsorption of ______.

Back 32

K+ and Na+

Front 33

saliva osmolality and pH are partly determined by _____________ rate

Back 33

saliva secretion

Front 34

which molecule(s) in saliva has the highest resting composition? what is the value?

Back 34

K+; 70 mEq/L

Front 35

which molecule(s) in saliva has the lowest resting composition? what is the value?

Back 35

Cl- and Na+; 15 mEq/L

Front 36

which molecule(s) in saliva is right in the middle when in resting composition? what is the value?

Back 36

HCO3; 30 mEq/L

Front 37

what are the physiological stimulators for salivary sectreion?

Back 37

conditioned reflexes: chewing, tasting, smelling, nausea

Front 38

what gland in the gastric mucosa produces HCl, pepsinogen, IF, and mucus?

Back 38

oxyntic gland

Front 39

what gland in the gastric mucosa produces mucus and gastrin?

Back 39

pyloric glands

Front 40

what section of the stomach contains oxyntic glands?

Back 40

fundus and body

Front 41

what section of the stomach contains pyloric glands?

Back 41

antrum

Front 42

what 6 things compose gastric juice?

Back 42

HCl, pepsinogen, gastric lipasem mucus, HCO3, and IF

Front 43

what are the functions of HCl?

Back 43

bactericidal (prevents GI infection), denature polypeptides, and it activates pepsinogen into pepsin

Front 44

what is the function of pepsinogen?

Back 44

pepsin initiates protein digestion

Front 45

what is the function of gastric lipase?

Back 45

fat digestion

Front 46

what are the functions of mucus and bicarb?

Back 46

lubricates chyme, the alkaline (pH =7) mucus layer is the gastric mucosal barrier, and buffers the gastric acid

Front 47

what is the function of IF?

Back 47

vitamin B12 absorption

Front 48

what type of cells produce pepsinogen?

Back 48

Chief cells

Front 49

what type of cells produce IF?

Back 49

parietal cells

Front 50

what is the pH level of the stomach post-prandially?

Back 50

pH< 1

Front 51

what is the pH level of the stomach when fasting?

Back 51

pH< 2

Front 52

when does basal secretion occur in the stomach?

Back 52

when fasting

Front 53

what is the neural stimuli for HCl secretion?

Back 53

Parasympathetic nervous system - ach

Front 54

what is the paracrine stimuli for HCl secretion?

Back 54

histamine

Front 55

what is the endocrine stimuli for HCl secretion?

Back 55

Gastrin

Front 56

what enzyme is used to produce H and bicarb from CO2 and water?

Back 56

carbonic anhydrase

Front 57

what four channels are involved in the secretion of HCl into the gastric lumen?

Back 57

H/K ATPASE, Na/K ATPase, HCO3/Cl- exchanger, Cl- channel

Front 58

when is gastric secretion maximal?

Back 58

1 hour after a meal

Front 59

what does high acidity of the stomach content inhibit? stimulate?

Back 59

inhibit: gastrin release; stimulate: release of somatostatin

Front 60

what is the major inhibitory hormone that inhibits gastric acid secretion 1 hour after a meal?

Back 60

secretin

Front 61

what are the 5 stimuli for inhibitory hormones secretion?

Back 61

acids, protein digestion products, fat, hyperosmotic fluids, and hypoosmotic fluids

Front 62

what reflex does the presence of food in the small intestine initiates? what is its function?

Back 62

a reverse enterogastric reflex that inhibits gastric secretion and stomach emptying

Front 63

what stimulates pepsinogen secretion?

Back 63

Ach (mainly via Vagal activation) and acid in the stomach lumen

Front 64

what increases pepsinogen secretion?

Back 64

secretin and gastrin

Front 65

which phase accounts for 20-30% of the total daily gastric secretion?

Back 65

cephalic phase

Front 66

via what type of receptors do vagal afferent fibers relay impulses? where are these receptors located?

Back 66

via mechanoreceptors and chemoreceptors. located in the oral and nasal cavities

Front 67

T/F
efferent fibers increase acid secretion through direct and indirect mechanisms.

Back 67

true

Front 68

what is the direct mechanism for regulatory efferent pathways in the cephalic phase?

Back 68

vagal input to parietal cells mediated by ACh- most potent

Front 69

what is the indirect mechanism for regulatory efferent pathways in the cephalic phase?

Back 69

G cell stimulation of gastrin release mediated by GRP, histamine release by ECL cell

Front 70

which phase accounts for 60-70% of the total daily gastric secretion?

Back 70

gastric phase

Front 71

what are the stimulatory signals of the gastric phase?

Back 71

mechanically through the wall distention, chemically through partially digested protein products in chyme (AA and peptides) , calcium, caffeine and alcohol.

Front 72

what are the three regulatory pathways in the gastric phase?

Back 72

vago-vagal (extrinsic), local intramural (enteric NS) and G-cell stimulation

Front 73

which phase is only responsible for less than 10% of the total daily gastric secretion?

Back 73

intestinal

Front 74

what are the stimulatory signals for the intestinal phase? which one is the major stimulus?

Back 74

distention of the intestinal wall, circulating AA and protein digestion products in chyme (AA and peptides). The major stimulus is circulating AAs.

Front 75

where do absorbed amino acids circulate in blood to during the intestinal phase?

Back 75

gastrin secreting cells (G-cell and parietal)

Front 76

what are the two regulatory pathways in the intestinal phase?

Back 76

gastrin and nervous mechanism

Front 77

what layer lubricates chyme and buffers gastric acid?

Back 77

alkaline mucus layer --> gastric mucosal barrier

Front 78

what are 5 the protective factors on gastroduodenal mucosa?

Back 78

mucus, bicarb, prostaglandins, mucosal blood flow and growth factors

Front 79

what are the 7 damaging factors on gastroduodenal mucosa?

Back 79

H+, pepsin, H.pylori, NSAIDs, stress, smoking and alcohol.

Front 80

what leaks into the mucosa after a damaged mucosal barrier?

Back 80

H+

Front 81

what types of cells are damaged by leaking H+? what will that cause?

Back 81

mucosal mast cells --> stimulating histamine release.

Front 82

what does histamine act on? what does it cause?

Back 82

mucosal capillaries and causes local ischemia, hypoxia and vascular stasis.

Front 83

Via what three mechanisms does H.pylori damage the mucosa?

Back 83

produces NH3 and various cytokines, increases H+ secretion: (increase in gastrin secretion and decrease in somatostatin secretion), and a decreases in bicarb secretion

Front 84

how do NSAIDs damage the mucosa?

Back 84

by decreasing mucosal production of prostaglandins by inhibiting COX and causing mucosal damage

Front 85

What do prostaglandins regulate?

Back 85

the secretion of mucus and bicarb

Front 86

what three factors contribute to peptic ulcer disease?

Back 86

H.pylori, NSAIDs, and Bile acid

Front 87

how does bile acid damage the mucosa?

Back 87

increase H+ leakage into the mucosa

Front 88

where percentage of the pancreas is composed of exocrine cells?

Back 88

90%

Front 89

what comprises the aqueous component of the pancreas? what is the function of this component?

Back 89

bicarb, water and electrolytes; optimize pH for digestive enzymes and prevent ulceration

Front 90

what comprises the enzymatic component? via what cells?

Back 90

digestive enzymes: amylase, lipase and proteases. Via acinar cells

Front 91

T/F
composition of pancreatic juice is independent of the secretory flow rate.

Back 91

FALSE: the composition is dependent on the secretory flow rate

Front 92

which phase has 20% of total stimulated pancreatic secretion?

Back 92

cephalic

Front 93

what are the stimulatory signals for pancreatic secretion in the cephalic phase? regulatory pathways?

Back 93

condition reflexes. Reg: vagal efferents to the pancreas (Ach)

Front 94

what phase is responsible for 5-10% of total stimulated pancreatic secretion?

Back 94

gastric

Front 95

what are the stimulatory signals for pancreatic secretion in the gastric phase? regulatory pathways?

Back 95

stim: gastric distension and digestive products of proteins. reg: vagal efferents (Ach)

Front 96

what is the most important phase in relation to pancreatic secretion? why?

Back 96

intestinal because it is responsible for 70-80% of total stimulated pancreatic secretion

Front 97

what are the stimulatory signals for pancreatic secretion in the intestinal phase? regulatory pathways?

Back 97

stim: gastric acid (H+), digestion products of fats and protein, distention and hypertonic fluids
reg: secretin, CCK, vagal efferents

Front 98

what is the major hormone involved in the regulation of pancreatic secretion? what is the stimuli and primary effect?

Back 98

secretin.
stimuli: acidic (pH <4.5-5) chyme in duodenum.
primary: increased Bicarb from pancreas and liver

Front 99

what is the non major hormone involved in the regulation of pancreatic secretion? what is the stimuli and primary effect?

Back 99

CCK.
stimli: AA, some peptides, fatty acids in small intestine
primary: increase in enymes secretion

Front 100

what is the stimuli for pancreatic secretion under neural regulation? what is the primary effect?

Back 100

stimuli: peptides, AAs
primary: increased enzyme secretion and increased aqueous secretion

Front 101

T/F
pancreatic enzyme secretion is able to adapt to the diet?

Back 101

true :)

Front 102

in a high protein, low carb diet, which one will increase: proteases or amylases?

Back 102

proteases

Front 103

what potentiates the secretory responses to CCK and secretin?

Back 103

insulin

Front 104

where are the cells that secrete fluid and electrolytes into the intestinal lumen usually housed?

Back 104

in the crypts of the mucosa

Front 105

how many L/day are secreted in the small intestine?

Back 105

1-2

Front 106

what are the components of the secretion from the colon?

Back 106

mucus, K+ and bicarb

Front 107

what are the functions of the intestinal secretion from the small intestine?

Back 107

chyme fluidity: digestion/absorption/motility, dilute toxins, and buffer