Gi And Liver Physio

Front 1

***what is the "really basic" function of the liver?

Back 1

to regulate the concentration of substances in hepatic venules and in bile

Front 2

what are the 5 major physiologic functions of the liver

Back 2

1. THE major organ of metabolism
2. detox/excretion
3. storage of nutrients (glycogen/fat)
4. immune reaction/phagocytosis
5. synthesis of structural proteins

Front 3

what two domesticated mammals don't have a gall bladder?

Back 3

horse and rat

Front 4

histologically, what is the major landmark to identify liver tissue?

Back 4

the portal triad

Front 5

what is the arrangement of cells in a liver lobule?

Back 5

cords of hepatocytes separated by sinusoids

Front 6

where does processed blood flow out of the liver lobule?

Back 6

central venule

Front 7

what is the functional unit of a liver lobule?

Back 7

acinus

Front 8

which zones of the liver lobule have the highest metabolism? Which have the lowest?

Back 8

the periportal cells have the highest; the cells surrounding the central vein have the lowest.

Front 9

what structures comprise the portal triad of the liver?

Back 9

- portal vein
- bile duct
- hepatic artery

Front 10

what chemical is commonly used to measure hepatic blood flow?

Back 10

indocyanin

Front 11

what can result from hepatic venule outflow obstruction?

Back 11

- ascites
- hepatomegaly
- elevated transaminases
- jaundice

Front 12

what can result from impaired intrahepatic blood flow?

Back 12

- ascites
- espohageal problems
- hepatomegaly
- elevated transaminases

Front 13

what can result from impaired blood inflow to the liver?

Back 13

- esophageal problems
- spelnomegaly
- intestinal congestion

Front 14

scarring of the liver

Back 14

cirrhosis

Front 15

true of false, the liver is a minor contributor to lymph?

Back 15

false. It is the major lymph-producing organ, generating approximately 50% of lymph.

Front 16

what things can happen if hepatic central venous pressure rises?

Back 16

- increased fluid leakage into the lymph
- fluid leakage from the liver surface
- in extreme cases, portal back pressure and gut edema

Front 17

the accumulation of protein enriched fluid in the peritoneal cavity as the result of fluid loss from the liver

Back 17

ascites

Front 18

***To what degree do liver cells differ from each other?

Back 18

- all cells have specialized functions and differ morphologically, even those of similar cell types
- function is compartmentalized

Front 19

how are liver cells functionally polarized?

Back 19

- one pole is in contact with hepatic sinusoids and engages in nutrient exchange, oxygen exchange, secretion, etc.
- the other pole is in direct contact with the ECM and adhere to collagen

Front 20

what are the two types of liver acini and what are their features?

Back 20

- structural acinus: portal triads at each of 6 (variable) corners, cords of hepatocites, sinusoids, central venule, and protal triads; reflects the vascular drainage of the liver

- functional acinus: portal triad in the center. Functionality is centralized around (1) the most oxygenated blood and (2) the portal vein.

Front 21

what are the three components of the liver functional acinus, and what do they do?

Back 21

1. central zone (periportal) - the most metabolically active cells because of oxygenation

2. midzonal region - hepatocytes between the portal triads and central venules; less metabolically active than the periportals and has different physiologic activity

3. centriolbular zone - hepatocytes arranged around the "central" venule, which is at the periphery of the FUNCTIONAL acinus; lowest metabolic activity because it is most distant from the oxygen source of the hepatic artery

Front 22

what is the "streaming liver theory?"

Back 22

hepatocytes originate near portal triands and move toward central venue, where they are apoptosed. This takes about 150 days in a human.

Front 23

what 3 things dictate the activity of a liver cell?

Back 23

1. position in the acinus
2. oxygen and nutrient supply (periportal cells use them up first)
3. differential gene expression

Front 24

which cells in the liver are most affected if oxygen or nutrient supply are diminished?

Back 24

the centrilobular zone (cells closest to the central venule) because the periportal cells use up the nurtients and oxygen first

Front 25

what are the predominant energy processes used by the liver just after eating and during fasting (e.g. before a meal)

Back 25

- after eating, more carbs --> glycolysis
- fasting, gluconeogenesis and glycogenolysis

Front 26

how do periportal hepatocytes differ in their carbohydrate metabolism versus centilobular hepatocytes?

Back 26

COMPARTMENTALIZED
- periportal: glycogenolysis and gluconeogenesis
- centrilobular: glycolysis and glycogen synthesis

Front 27

what three major things does the hepatocyte do with glucose once it is inside the cell?

Back 27

1. hepatocyte metabolism
2. glycogenesis
3. lipogenesis

Front 28

What five major ways does the liver use fatty acids?

Back 28

1. oxidation for metabolic energy
2. converted to trigs by esterification
3. synthesized into phospholipids
4. synthesized into cholesterol
5. synthesized into VLDLs

Front 29

how do periportal hepatocytes differ in their lipid metabolism versus centilobular hepatocytes?

Back 29

- periportal: cholesterol synthesis
- centrilobular: lipogenesis

Front 30

what is the major organ for protein synthesis and what is the major protein?

Back 30

- liver
- albumin

Front 31

what is the primary function of the liver with regards to protein metabolism?

Back 31

to maintain a constant level of free amino acids in the bloodstream

Front 32

how do amino acids move from the plasma to the hepatocytes?

Back 32

active transport

Front 33

what happens to excess amino acids in the liver?

Back 33

- deaminated and converted to fats or carbs

Front 34

where, specifically in the liver lobule is ammonia converted to urea?

Back 34

the proximal half to 2/3rd of the acinus

Front 35

what causes hepatic encephalopathy?

Back 35

inadequate ammonia detoxification by the liver

Front 36

true or false, the liver synthesizes immunogloubulins?

Back 36

false. The liver does make a protein for IgA, however.

Front 37

name five major proteins made in the liver

Back 37

1. albumin
2. glycoproteins
3. clotting factors
4. fibrinogen
5. secretory component of IgA

Front 38

what is the physiological purpose of putting a sugar residue onto a protein to make a glycoprotein?

Back 38

the sugar residue determines which cell will use it.

Front 39

synthesis of which of the six clotting factors are dependent on Vitamin K?

Back 39

all of them

Front 40

what major problem can happen in the deficiency of vitamin K?

Back 40

the inability of the liver to synthesize clotting factors and thus the animal can bleed to death.

Front 41

why is vitamin K important in the synthesis of clotting factors?

Back 41

it is required for the synthesis of a special amino acid residue.

(glutamic acid is converted to gamma-carboxyglutamic acid)

Front 42

what chemical causes the polymerization of fibrinogen to fibrin?

Back 42

thrombin

Front 43

what is the molecule "tagged onto" proteins for non-lysosomal degradation?

Back 43

ubiquitin

Front 44

what hormones stimulate protein degradation by the liver?

Back 44

glucagon, catecholamines, glucocorticoids

Front 45

what is the basic process of detoxification by the liver?

Back 45

The toxic substance goes through a Phase I reaction, then a Phase II reaction, which makes them water-soluble, and excreted in the bile

Front 46

what is induction and what change in intracellular structure accompanies it?

Back 46

resistance to drugs by increased ability to detoxify in the liver. SER hypertrophy is seen in induction.

Front 47

what is the liver's role in immunity?

Back 47

- Kupffer cells are very good at phagocytosing bacteria
- The liver produces the secretory component of IgA

Front 48

what are the two major functions of bile?

Back 48

1. facilitation of fat digestion and absorption
2. elimination of waste products from the circulation

Front 49

what makes poop brown-green?

Back 49

bile

Front 50

why is conjugation of bile necessary?

Back 50

conjugation allows bile to be water soluble and fat soluble to emulsify fat (in micelles) in the small intestine and facilitate absorption

Front 51

what are the six basic components of bile?

Back 51

1. water
2. bile salts
3. bilirubin
4. cholesterol
5. lecithin
6. electrolytes

Front 52

what is the precursor molecule for bile salts?

Back 52

cholesterol

Front 53

to what two locations does the liver transport bile?

Back 53

1. small intestine
2. gall bladder

Front 54

true or false, the gallbladder is muscular and can secrete amounts of bile based on what is needed?

Back 54

true

Front 55

true or false, the gallbladder actively dilutes bile to make more of it?

Back 55

false. The gallbladder concentrates bile to make it more potent

Front 56

what are the three major factors controlling gallbladder contraction?

Back 56

1. cholecystokinin (CCK)
2. vagal and ENS innervation
3. amount of dietary fat

Front 57

true or false, most bile is reabsorbed in the small intestine by passive and active transport?

Back 57

true.

Duodenum and jejumum: passive
Ileum: active

Front 58

what is the major component of gallstones?

Back 58

cholesterol

Front 59

true or false, bile activity can be either enzymatic or non-enzymatic, depending on function?

Back 59

false. It is non-enzymatic.

Front 60

Name NINE functions of the alimentary tract (yes, nine)

Back 60

1. ingestion
2. digestion
3. absorption
4. elimination
5. detox
6. bacterial housing/management
7. immune function
8. secretion
9. endocrine function

Front 61

what is the most essential function of bacterial housing and management in the lower GI tract?

Back 61

to keep bacteria out of the blood and small intestine

Front 62

what is secreted by the alimentary tract?

Back 62

- hormones
- HCl
- bicarb
- enzymes
- electrolytes
- "water"

Front 63

what is the difference between digestion and absorption

Back 63

digestion is the mechanical or chemical breakdown of food into smaller components. Absorption is taking those components and putting them into the system.

Front 64

true or false, digestion and absorption, by and large, are controlled by the same set of stimuli?

Back 64

false. they are controlled by completely different and distinct processes.

Front 65

what are the three phases of digestion?

Back 65

1. Luminal phase - food is broken down in the lumen
2. Mucosal phase - food is broken down enzymatically in the small intestine on the surface of the enterocyte brush borders
3. Intracellular digestion - within the enterocytes of the small intestine

Front 66

what is the one phase of absorption?

Back 66

1. Transport phase - passage into the vascular system

Front 67

what are the three regulators of the GI tract

Back 67

1. neuroendocrine - the intrinsic ENS of the GI tract
2. CNS - parasympathetic (vagus & pelvic nn.) and sympathetic (splanchnic & hypogastric nn.)
3. GI reflexes

Front 68

in what direction do GI reflexes generally move?

Back 68

oral to aboral

Front 69

true or false, the CNS, under extreme circumstances can completely override the ENS and GI reflexes?

Back 69

false

Front 70

what is the name of and distribution of GI endocrine tissue?

Back 70

- APUD or enteroendocrine cells
- dispersed diffusely through the stomach, SI, and pancreas.
- most abdundant orally; decreases aborally

Front 71

what class of hormones are the GI endocrine horomones?

Back 71

peptide/protein

Front 72

where are GI endocrine hormones secreted?

Back 72

into the basolateral membrane, where they can diffuse and have autocrine, panacrine, or exocrine effects

Front 73

what electrolytes are secreted by the stomach?

Back 73

only H+ and Cl- to any significant extent

Front 74

what are the four major ions absorbed and/or secreted by the intestines?

Back 74

Na, K, Cl, HCO3

Front 75

what are the three general goals of electrolyte transport in the gut?

Back 75

1. provide the appropriate substrates for various processes (e.g. make gastric acid in the stomach; provide bicarb in the duodenum to neutralize the acid)
2. maintain the correct pH
3. maintain the correct "magic" osmolality of 300 OsM

Front 76

what three major features of the gut facilitate the movement of ions and water?

Back 76

1. electrochemical gradients
2. high capillary permeability with low flow resistance
3. continuous flow through capillaries

Front 77

what are the four passive transport mechanisms used by the gut?

Back 77

1. paracellular (through the "leaky" tight junctions)
2. ion channels
3. facilitated diffusion
4. solvent drag

Front 78

what are the major substances transported by the gut with secondary active transport?

Back 78

- sodium
- chloride
- potassium
- bicarbonate
- glucose (and other sugars)
- amino acids

Front 79

what is tertiary active transport?

Back 79

active transport that relies most directly on the gradient established by a secondary active transport.

Example:
- Primary Na-K-ATPase decreases sodium in the cell-->
- Secondary: Because of decreased sodium in the cell, Na from the lumen raises the level of bicarb in the cell by an Na-H symporter -->
- Tertiary: because of the high levels of intracellular bicarb, a Cl-bicarb antiporter transports chloride into the cell and bicarb out.

Front 80

how does regional absorption of water vary by species type?

Back 80

- Carnivores: greatest volume in the small intestine
- Horses: greatest volume in the large intestine
- Ruminants and Pigs: intermediate

Front 81

what is the primary reason that water flows in any particular direction in the gut?

Back 81

to keep the gut isoosmotic

Front 82

in carvnivores, why is water "secreted" into the gut in "early" intestine, but absorbed in the "late" intestine?

Back 82

the intestine wants to be isoosmotic:
- early in the intestine, there are more particles to dilute and thus more water is needed to keep it 300 mOsm
- late in the intestine, most of the particles have been absorbed, so water must be reabsorbed to keep the lumen 300 mOsm

Front 83

where, specifically, does most electrolyte absorption occur in the GI tract?

Back 83

the enteric luminal surface; brush borders increase the surface area

Front 84

what is the most important electrolyte involved in GI absorption?

Back 84

sodium

Front 85

in what three ways is chloride absorbed in the GI tract?

Back 85

- paracellular
- ion channels
- secondary and tertiary active

Front 86

how is bicarbonate directly absorbed in the GI tract?

Back 86

- an ion exchange mechanism

Front 87

in what two ways is postassium absorbed in the gut?

Back 87

- mainly passive paracellular diffusion
- H-K ATPase in the colon recovers the "last bit" when needed

Front 88

what is the main function of the crypt cells in the intestinal tract?

Back 88

to SECRETE electrolytes and "water"

Front 89

what microanatomical structures of the intestines secrete electrolyte and by what physiological process does this occur?

Back 89

- the intestinal crypt cells
- a Na and Cl pumping mechanism on the basolateral membrane directed into the cells. Water follows.

Front 90

Why is intestinal secretion important?

Back 90

to maintain the 300 mOsm value in the presence of large amounts of osmotically active particles.

Front 91

what are the two functions of mastication?

Back 91

1. divide food particles
2. mixes the food with saliva

Front 92

what are the main components of saliva and species differences

Back 92

ALL:
1. water
2. salts
3. mucin: a slippery protein

PIGS, apes, guinea pig, rodents: salivary amylase

Front 93

what are the five major functions of saliva in non-ruminants?

Back 93

- moisten and lubricate food for sawllowing
- dissolve molecules for taste buds
- cleanses mouth and teeth
- antibiotic activity
- (varies) digests starch with amylase

Front 94

what controls secretion and what three things stimulate this process

Back 94

Secretion is controlled neurally:
1. parasympathetic input
2. object in mouth as a reflexive secretion
3. anticipation of food

Front 95

what are the voluntary parts of deglutition?

Back 95

from tongue, pushing bolus to pharynx

Front 96

what initiates swallowing?

Back 96

involuntary pharyngeal receptors triggering swallowing centers

Front 97

what is the condition of esophageal sphincters when swallowing is not occuring?

Back 97

- held tonically closed
- they must relax to swallow

Front 98

what are the two main functions of the upper esophageal sphincter?

Back 98

1. prevents reflux to pharynx during swallowing
2. prevents air entry into the esophagus during breathing

Front 99

what is the function of the lower esophageal sphincter?

Back 99

prevents gastric reflux to the espohagus

Front 100

what is the difference between primary and secondary peristalsis?

Back 100

- primary is elicited by swallowing
- secondary is when food is stuck in the esophgaus and stretch recep

Front 101

what are the two major causes of megaesophagus?

Back 101

1. failure of the lower esophageal sphincter to relax
2. a persistent right aorta

Front 102

comment on the absorption in the simple stomach.

Back 102

- limited
- small amounts of water, some drugs (e.g. NSAIDs), ethanol :-)

Front 103

what are the two basic types of mucus in the simple stomach and what is their function

Back 103

1. thick - protective
2. thinner - lubrication

Front 104

what is the "milk curdling" enzyme of the stomach that is especially important in young animals?

Back 104

chymosin (rennin)

Front 105

what are pepsins, where are they secreted, and how are they activated?

Back 105

gasteric enzymes of the stomach, secreted as zymogens, are converted to their active form by gastric HCl

Front 106

an enzyme precursor secreted in the stomach that is activated by gastric acid

Back 106

zymogen

Front 107

***what is the action of gastric lipase?

Back 107

cleaves the lipid off of a lipoprotein. It does not digest the lipid!

Front 108

***where is gastrin produced, released, and what is its action?

Back 108

- produced by the APUD cells in the stomach
- released into the blood
- acts in increase acid and pepsin secretion in the stomach
- stimulates gastric motility
- small trophic effect on gastric mucosa

Front 109

what stimulates the secretion of gastrin?

Back 109

- luminal factors: protein digestion
- mural (muscular wall) factors: vagal discharge caused by gastric stretch and contraction
- a POSTIVE FEEDBACK mechanism

Front 110

what inhibits the secretion of gastrin?

Back 110

- luminal factors: increased gastric acid
- mural factors: loss of stomach wall stretch
- hormonal factors released by small intestine: secretin, GIP (gastric inhibitory peptide)

Front 111

where in the stomach is histamine produced, what stimulates it, and what effect does it have?

Back 111

- produced by gastric mast cells in response to gastrin or acetocholine
- has a panacrine effect to stimulate more gastrin release

Front 112

what domestic mammals (besides humans) produce intrinsic factor, and what is its function?

Back 112

- produced by pigs and rodents
- allows B12 absorption in the ileum

Front 113

true or false: H and Cl are secreted separately in the stomach and require active transport

Back 113

true

Front 114

What is the basic process of HCl secretion into the gastric lumen?

Back 114

1. carbonic anhydrase makes H+ and bicarb in the stomach from water and CO2
2. H-K ATPase actively transports H+ into the stomach and K+ out
3. The remaining bicarb is exchanged for a chloride in the blood by an antiporter
4. chloride is moved through a chloride channel in the apical membrane

Front 115

what are the three main chemical regulators of gastric acid secretion?

Back 115

1. Acetylcholine: vagal discharge induced by stretch and contraction receptors in the stomach wall up-regulates gastrin.
2. gastrin up-regulates acid
3. histamine up-regulates gastrin

Front 116

true or false, maximal gastric acid release is accomplished when acetylcholine vagal receptors, gastrin receptors, and histamine receptors are simultaneously stimulated.

Back 116

true

Front 117

what is the most important mechanism that prevents the overproduction of gastric acid?

Back 117

the negative feedback mechanism controlled by low pH of the gastric lumen.
- pH 2, acid slows down
- pH 1, acid stops

Front 118

***which macronutrients (carbs, proteins, lipids) are significantly digested in the stomach?

Back 118

all of them

Front 119

what nutrients are almost completely digested chemically in the stomach

Back 119

only protein

Front 120

what are three major features that protect the stomach from digesting itself under acidic conditions?

Back 120

1. very tight junctions
2. very high electrical resistance of the apical membranes that push away H+
3. thick mucous

Front 121

why is protein digestion in the stomach critical?

Back 121

because the pancreatic enzymes cannot digest large proteins

Front 122

what are the four main functions of gastric motility?

Back 122

1. filling/storage (stretch relaxation)
2. mechanical digestion (peristalsis and reverse peristalsis)
3. initiation of chemical digestion by mixing digesta with acid and pepsins
4. controlled emptying

Front 123

what are the major functions of the gastric fundus?

Back 123

- stretch relaxation to store volumes of food without increase in pressure
- mild peristalsis to slowly deliver food to body and antrum
- no mechanical mixing so species with salivary amylase can do their thing

Front 124

where is the gastric pacemaker?

Back 124

near the fundus

Front 125

what is characteristic of the peristalsis in the body of the stomach?

Back 125

strong for vigorous mixing

Front 126

what is characteristic of the peristalsis in the pyloric antrum of the stomach?

Back 126

really, really strong, grinding contractions to make small bits.

Front 127

besides mechanical and chemical digestion, what is the other major function of the pyloric antrum?

Back 127

- delivers small bits to the pylorus
- delivers bigger bits to the body of the stomach for further digestion

Front 128

what is the size of the particle that gets through the pylorus during normal digestion?

Back 128

< 2 mm

Front 129

how does sympathetic stimulus affect the stomach during digestion?

Back 129

slows gastric emptying

Front 130

what comprises the enterogastric reflex?

Back 130

- duodenal osmoreceptors
- hypertonic contents slow emptying
- isotonic contents maximize emptying

Front 131

how does pH in the duodenum affect gastric emptying?

Back 131

- anything below pH 3.5 stops; anything lower would be too acidic for the duodenum to neutralize.

Front 132

how do small intestinal hormones affect gastric emptying?

Back 132

slows it down

Front 133

what are interdigestive contractions?

Back 133

in between meals, moves larger objects (like tennis balls) into the duodenum

Front 134

***what are the three phases of gastric secretion?

Back 134

1. cephalic
2. gastric
3. intestinal

Front 135

how does the cephalic phase of gastric secretion affect gastric activity and by what means?

Back 135

- promotes gastric activity
- CNS-mediated (sight, smell, thought)
- increases motility and secretion

Front 136

how does the gastric phase of gastric secretion affect gastric activity and what happens during this phase?

Back 136

- promotes gastric activity
- local reflexes and responses to gastrin
- results from presence of food in the stomach

Front 137

how does the intestinal phase of gastric secretion affect gastric activity and what happens during this phase?

Back 137

- inhibits gastric activity (don't want to overload the duodenum)
- reflex negative feedback - enterogastric reflex
- hormonal feedback - GIP and CCK lower HCl, pepsinogen, motility

Front 138

what is the regulator of conscious (skeletal muscle) GI motility?

Back 138

spinal nerve innervation

Front 139

what are the regulators of unconscious (smooth muscle) GI motility?

Back 139

extrinsic factors: parasympathetic and sympathetic innervation; myenteric plexuses

intrinsic factors: hormones produced by the GI tract itself - most influence secretion, but some influence motility

Front 140

what are the two critical components of intrinsic gut motility?

Back 140

cooperation between:
1. inherent electrical activity of the smooth muscle cells
2. the gut's ENS

Front 141

what acts as the pacemaker for gut slow wave contractions?

Back 141

duodenum

Front 142

true or false, the CNS cannot control GI slow waves, but ENS stimulation can increase, decrease, or stop them

Back 142

false. The slow waves are completely independent of all nervous input

Front 143

true or false: slow waves require neural input to make the gut wall contract.

Back 143

true. slow waves are moving constantly, but they cannot cause a contraction by themselves

Front 144

***what affects the contractility of intestinal smooth muscle?

Back 144

- hormomes from APUD cells
and/or
- neuroregulatory substances from the ENS

they change the resting potential of the slow waves

Front 145

how does parasympathetic stimulus affect GI motility?

Back 145

- promotes GI secretion and motility
- relaxes GI sphincters and blood vessels

Front 146

how does sympathetic stimulus affect GI motility?

Back 146

- inhibits GI motility and secretion
- contracts sphincters and blood vessels

Front 147

what are the two major functions of reverse peristalsis?

Back 147

- get digesta into the cecum
- temporarily retain digesta in a particular region

Front 148

non-progressive contractions of alternating segments of circular muscle layer in the intestines

Back 148

mixing-segmentation

"gooshes" contents back and forth

Front 149

holding digesta without allowing any movement

Back 149

retention

Front 150

How do secretin and CCK affect one another?

Back 150

They augment one another's release

Front 151

where is CCK produced and released? What stimulates its secretion? What are its effects?

Back 151

(cholecystokinin)
- produced by most of the duodenum in response to the presence of digesta in the lumen
- stimulates the acini of the exocrine pancreas to secrete enzyme-rich fluid
- is a weak stimulator of bicarb secretion

Front 152

where is secretin produced and released? What stimulates its secretion? What are its effects?

Back 152

- produced and released by the first few cm of the duodenum in response to gastric acid
- stimulates the ducts of the exocrine pancreas to produce copious amounts of bicarb
- weak stimulator of bile and pancreatic enzymes

Front 153

what are the two hormones that control exocrine pancreas secretion and where are they produced?

Back 153

secretin and cholecystokinin (CCK) produced by the small inestine - especially the duodenum.

Front 154

What effect does neural stimulation have on bicarb secretion by the exocrine pancreas?

Back 154

Little to none

Front 155

what two major functions does the intrinsic GI nervous system provide to control exocrine pancreas secretion?

Back 155

1. stimulates pancreas acinar cells (zymogens)
2. reinforces cephalic and gastric phases

Front 156

how does vagal stimulation control pancreatic secretion, what types of neurons are they, and what factors activate them?

Back 156

secretory branches of the vagus nerve stimulate pancreatic secretion. They are affected by sight/smell of food (cephalic phase) and gastric distension (gastric phase).

Front 157

what are the three general physiologic controls of exocrine pancreatic secretion

Back 157

1. vagal stimulation
2. intrinsic GI nervous stimulation
3. endocrine stimulation from the small intestine

Front 158

what is the most common pathogenesis of pancreatitis?

Back 158

the pancreas is overstimulated and produces many enzymes due to loss of normal pancreatic inhibition. In this case, trypsinogen will be cleaved to trypsin in the pancreas, activating the pancreatic enzymes inside the pancreas. The result is the pancreas digesting itself.

Front 159

what is the function of trypsin?

Back 159

to cleave zymogens secreted into the intestinal lumen to active enzymes. Also, it cleaves trypsinogen to trypsin.

Front 160

what two enzymes cleave trypsinogen to trypsin?

Back 160

1. enteropeptidase
2. trypsin

Front 161

***true or false: endopeptidase cleaves trypsinogen to trypsin in the duodenum?

Back 161

false. ENTEROpeptidase does this.

Front 162

how is acid-base balance in the lumen and blood accompished by the stomach and pancreas?

Back 162

with carbonic anhydrase ("CA"), CO2, and water:

- the gastric parietal cells secrete H+ into the gastric lumen and bicarb into the blood

- the pancreatic ducts secrete bicarb from the blood into the duodenal lumen, producing carbonic acid, which is catalyzed back to water and CO2 by CA.

Front 163

which pancreatic digestive enzymes are secreted in their active forms?

Back 163

only pancreatic amylase

Front 164

what are the four major lipid digesting enzymes produced by the exocrine pancreas?

Back 164

1. pancreatic lipase
2. pancreatic co-lipase
3. cholestrol esterase
4. phoshpholipase

Front 165

true or false: any specific enzyme secreted by the pancreas can digest a variety of different chemical bond types, thus making them very powerful in digestion.

Back 165

false. Each specific enzyme cleaves a specific bond type.

Front 166

name the zymogen form for the following enzymes:

1. trypsin
2. chymotrypsin
3. elastase
4. carboxypeptidase A
5. DNAse

Back 166

1. trypsinogen
2. chymotrypsinogen
3. proelastase
4. procarboxypeptidase A
5. proDNAse

Front 167

how are nucleic acids digested?

Back 167

by DNAses and RNAses, which are secreted as proenzymes by the exocrine pancreas.

Front 168

What is another name for a proenzyme?

Back 168

zymogen

Front 169

what is the general name for the inert proteins secreted by the exocrine pancreas, where are they secreted, and what happens to them when they are secreted?

Back 169

Proenzymes are produced and secreted by the acinar cells of the exocrine pancreas, secreted into the small intestine, and cleaved into active enzymes by trypsin.

Front 170

what are the two histological divisions of the exocrine pancreas and what is the function of each unit?

Back 170

1. acinar cells - produce, secrete, and store digestive proenzymes. Proenzyme rich and bicarb poor

2. ducts - produce and secrete bicarbonate. Bicarb rich and proenzyme poor

Front 171

what are the two major functions of the exocrine pancreas?

Back 171

1. contribute to luminal enzymatic digestion of food nutrients
2. buffer digesta entering the SI

Front 172

Which "part" of the pancreas is associated with digestive secretions?

Back 172

Exocrine pancreas