GI 4 Flashcards
1
Q
More than —% of pancreas is exocrine:
– Acinar cells synthesize
and secrete
– Duct cells secrete
A
90
hydrolases for digestion
bicarbonate and water
2
Q
Luminal digestion of (3)
– Impaired function causes (2)
A
carbohydrate, protein, fat.
maldigestion and malabsorption.
3
Q
Neutralizes gastric H+:
secretes HCO3- into
duodenum up to
A
145 mEq/L
4
Q
Proteolytic enzymes synthesized, stored and secreted as inactive precursors. - Activated in intestinal lumen (2)
A
- Enterokinase
2. Trypsin
5
Q
—- synthesized, stored and
secreted with precursors.
A
Trypsin inhibitor
6
Q
Regulation of Acinar Cell Secretion
Function =
A
Digestive Enzyme Secretion
7
Q
Two Stimuli for Acini Cell Enzyme Secretion (2)
A
- CCK
2. ACh/GRP (vagovagal reflex)
8
Q
Two Stimuli for Ductal Cell
Secretion of H2O and HCO3- (2)
A
- *Secretin (Secretin receptor).
2. Ach (M3 receptor).
9
Q
Secretin (4)
A
cAMP Phosphorylation of CFTR increase Cl- conductance increase HCO3- secretion
10
Q
Secretin released when pH
A
< 4.5.
11
Q
Below pH = 3,
A
secretin release is maximal in segment of duodenum. Further release of secretin depends upon area of small intestine affected. (Maximal bicarbonate response is 30 mEq/hr)
12
Q
During meal pH rarely
A
< 3.5 or 4.0.
13
Q
Phases of Pancreatic Secretion (3)
A
Cephalic (20%)
Gastric (5-10%)
Intestinal (70-80%)
14
Q
Cephalic (20%)
Gastric (5-10%)
Both phases mediated by
A
vagovagal
reflex - low volume, high enzyme
secretion (Ach/GRP)
15
Q
(2) both potentiate the effects of secretin on water and
bicarbonate secretion.
A
CCK and Ach
16
Q
Secretion Rate α
A
[Secretin] + [Ach] + [CCK]
17
Q
Low secretion rates - (2)
A
bicarbonate concentration is low
chloride concentration is high
18
Q
High secretion rates - (2)
A
bicarbonate concentration is high
chloride concentration is low
19
Q
Sodium and potassium concentrations
always same as —
A
plasma
20
Q
Pancreatic juice is —
A
isotonic
21
Q
Cystic Fibrosis (3)
A
Abnormal sweat composition. Decreased pulmonary and pancreatic secretion. Mendelian autosomal recessive occurrence.
22
Q
Defective CFTR: (3)
A
– Sweat Cl- reabsorption;
– Pancreatic duct cell function;
– Pulmonary mucus clearance.
23
Q
Disorders of Exocrine Pancreatic
Function (3)
A
Cystic Fibrosis
Pancreatitis
Duct Obstruction
24
Q
Pancreatitis (4)
A
– Acute and chronic – Trypsin activation causes pain, inflammation – Chronic disease destroys acini – Consequences reflect decreased digestive enzyme production
25
Duct Obstruction (2)
– Gallstones
| – Tumors
26
Without pancreatic
| enzymes - (2)
```
60% fat not absorbed
(steatorrhea)
30-40% protein and
carbohydrates not
absorbed
```
27
Functional Unit of liver =
Liver
| Lobule
28
```
skipped
Hepatic Function (7)
```
Cleansing and storage of blood
Metabolism of nutrients
Synthesis of proteins (coagulation factors,
plasma proteins, angiotensinogen)
Metabolism of hormones, chemicals
Storage of energy, vitamins, iron
Excretion of lipid-soluble waste products
Marked capacity for cellular regeneration
29
Secretion of bile –
600-1000 ml/day
30
Liver Has High Blood and Lymph Flow
| Total blood input approaches
1,350 ml/min (27% of resting
| cardiac output).
31
Liver Has High Blood and Lymph Flow
Resistance of vessels to blood
flow very ---
low
32
Cirrhosis increases resistance,
| produces
portal hypertension.
33
Hepatic lymph accounts for --%
| of total body production.
50
34
Increased vascular resistance can
| cause ---.
ascites
35
Role of Bile (2)
```
1. Bile salts (acids) and
lecithin required for
digestion (emulsification)
and absorption (micelles) of
dietary fat.
2. Excretion of lipophilic
metabolites (bilirubin),
excess cholesterol, other
waste products, drugs, and
toxins.
```
36
Hepatocytes secrete (5)
```
bile salts,
cholesterol,
lecithin,
bilirubin,
many other lipophilic substances.
```
37
Duct epithelial cells modify ---, add ---
primary secretion
| HCO3-
38
Storage and concentration in ---.
gallbladder
39
--- circulation reabsorbs some
| components.
Enterohepatic
40
Hepatocytes secrete
organic component of
bile into bile ducts (3)
- Bile Salts (produced
from cholesterol)
- Cholesterol
- Organic substances
41
Bile Duct cells secrete (3)
water, Na+ and HCO3-
42
Bile Transported (2)
1. Small intestine for
2. Gall Bladder for
fat digestion
| storage
43
Bile secreted --- by liver
continually
44
Most stored in
```
Gall Bladder
(max. volume = 30-60 ml)
```
45
12 hours of liver bile secretion
| or --- ml bile (concentrated)
450
46
(2) reabsorbed from bile while in
Gall Bladder (5-20x more
concentrated)
Electrolytes and water
47
Cholecystectomy (2)
No problems with fat digestion
| Bile flow directly into duodenum
48
Enterohepatic Circulation Conserves Bile Salts
Substance secreted into
bile by
hepatocytes.
49
Enterohepatic Circulation Conserves Bile Salts
Delivered to lumen of
---, then reabsorbed.
ileum
50
Enterohepatic Circulation Conserves Bile Salts
Transported to
hepatocytes via ---
sinusoids
51
Enterohepatic Circulation Conserves Bile Salts
---% of bile salts
recirculated
94
52
Enterohepatic Circulation Conserves Bile Salts
Bile salts circulate --x
before lost in feces.
17x
53
Active absorption: (2)
Apical sodium-dependent bile salt
transporter (ASBT)
ASBT also present in renal PT
54
BARI (Bile Acid Reabsorption Inhibitors) (4)
Drugs that inhibit Bile Recycling
Used to lower LDL levels in blood
Hepatocyte production of bile increases
6-10x if bile salt recycling reduced.
LDL taken up from blood via hepatocytes
as source of cholesterol for bile salts
55
Types:
| 1. Bile acid sequestrants
Bind to bile salts in intestinal lumen and
| block transport
56
Benefits: (2)
Drugs work in intestinal lumen (do not
need to be absorbed)
Reduce harmful side effects
57
Low ASBT Activity Associated with: (4)
Crohn’s disease
Congenital 1° bile acid malabsorption
Idiopathic chronic diarrhea
Irritable Bowel Syndrome
58
Hepatocyte dysfunction impairs (2) secretion:
bilirubin, bile salt
59
Hepatocyte dysfunction impairs bilirubin, bile
| salt secretion: (2)
– Drugs (acetaminophen), viral hepatitis, toxins;
| – Fibrosis, cirrhosis.
60
Duct obstruction: (2)
– Gallstones, tumors.
61
Intestinal mucosal defects impair`
bile salt
| reabsorption.
62
Stimuli for Gut Hormone Secretion
| Gastrin (stomach) (3)
amino acids and peptides
distention
(H+ inhibits)
63
Stimuli for Gut Hormone Secretion
| Ghrelin (stomach) (2)
absence of nutrients
| (inhibited by stretch)
64
Stimuli for Gut Hormone Secretion
| Secretin (Small Intestine) (1)
H+
65
Stimuli for Gut Hormone Secretion
| CCK (Small Intestine) (3)
amino acids and peptides
fatty acids
Indirectly via secretion of CCK-
RP and Monitor peptide
66
Stimuli for Gut Hormone Secretion
| GIP, GLP-1 (Small intestine) (1)
Glucose
67
Stimuli for Gut Hormone Secretion
| Motilin (Small Intestine) (2)
stimulus unknown
some studies suggest that an
alkaline pH in the duodenum
stimulates its release.
68
Endocrine Regulation: Specific Actions of Each Hormone
| Gastrin (4)
↑ Histamine Release (ECL cell)
↑ H+ Secretion (Parietal Cell)
↑ Gastric emptying
Trophic affects on Mucosa
69
Endocrine Regulation: Specific Actions of Each Hormone
| Ghrelin (1)
↑ Hunger
70
Endocrine Regulation: Specific Actions of Each Hormone
| Motilin (2)
↑ Gastric Motility (MMC/Fasting)
| ↑ Intestinal Motility (MMC/Fasting)
71
Endocrine Regulation: Specific Actions of Each Hormone
| GIP, GLP-1 (3)
↑ Insulin response to glucose
↓ Gastric Acid Secretion
↓ Gastric emptying
72
Endocrine Regulation: Specific Actions of Each Hormone
| Secretin (4)
↑ Panc & Biliary HCO3- secretion
Trophic affects on Exo. Pancreas
↓ Gastric Acid Secretion
↓ Gastric emptying
73
skipped
Endocrine Regulation: Specific Actions of Each Hormone
CCK (7)
```
↑ Pancreatic enzyme secretion
↑ Gall Bladder Contraction
Trophic affects on Exo. Pancreas
↓ Gastric emptying
↓ Gastric Acid Secretion
Relaxation of Sphincter of Oddi
Gastric receptive relaxation
```
