1
Q
how much bile does the liver produce?
A
up to 1L per day
2
Q
what is bile production stimulated by?
A
- secretin
- enterohepatic bile salt return
3
Q
what is the function of bile?
A
- elimination of wastes
- emulsification of intestinal lipids
4
Q
what stimulates the intestinal hormone secretin?
A
acidic chyme in the duodenum
5
Q
What are the actions of secretin on the stomach?
A
decrease gastric secretion and motility
6
Q
what is the action of secretion on the liver?
A
bile production
7
Q
what is the composition of bile?
A
- 97% water
- bile salts
- electrolytes
- FA
- cholesterol
- phospholipids
- bilirubin
8
Q
what is bile salt?
A
- conjugated bile acid in deprotonated form (cations)
- it is not excreted but returned to the liver
- contain bile acids
9
Q
bile acids
A
- produced by normal flora
- produced by cytochrome p450 mediated oxidation of cholesterol
- insoluble unless congugated
10
Q
what must bile acids be conjugated with in order to be soluble?
A
- taurine or
- glycine
11
Q
bilirubin
A
- breakdown product of heme
- released from splenic macrophages
- congugated in liver to glucuronid which is more water soluble
- eliminated in feces
- some returns to liver
- can also be eliminated in urine
12
Q
gall bladder
A
- thin walled muscular sac that lays in the ventral surface of the liver
- functions to store and concentrate bile (up to 10X)
- capacity: 30-40 mL
13
Q
describe the route of the biliary tree
A
- left and right hepatic ducts merge to form common hepatic duct
- common hepatic duct and cystic duct merge to form common bile duct
- common bile duct and main pancreatic duct merge at hepatopancreatic ampulla in duodenum
14
Q
what are the 2 sources of gall bladder contraction and therefore bile release?
A
- vagal stimulation (weakly)
- CCK (mainly)
15
Q
CCK actions
A
- gall bladder contraction
- sphincter of Oddi relaxation
- pancreatic secretions
16
Q
what stimulates the action of CCK?
A
fatty chyme in the duodendum
17
Q
What happens after bile is released into the duodenum?
A
- it mixes w/ chyme and intestinal juices
- bile salts emulsify fats for absorption
- remainder of bile is eliminated in feces
18
Q
monomer
A
- monoshaccharides
- glucose, fructose, galactose
19
Q
polymers
A
- disaccharides
- lactose, maltose, sucrose
20
Q
starches
A
- glucose polymers
- amylopectin
- salivary amylase
- pancreatic amylase
21
Q
What is the important take away for digestion/absorption of carbohydrates?
A
there is an enzyme for each specific thing
i. e:
- lactose enzyme = lactase (SI)
- maltose enzyme = maltase (SI)
- sucrose enzyme = sucrase (SI)
22
Q
Where does carb absorption occur?
A
along the length of the SI
23
Q
In terms of carb absorption, what happens at the apical surface of SI cells?
A
-Glucose, galactose and fructose all move in to the cell
24
Q
How are glucose and galactose transported into the epithelial cells along the SI?
- name of transporter
- type of transport
A
- by SGLT-1
- Na is high in the lume, moves along concentration gradient into cell
- secondary active transport
25
How is fructose moved into the SI cells?
- name of transporter
- type of transport
- GLUT-5
| - facilitated transport
26
In terms of carb absorption, what happens at the basal surface of cells in SI?
- contents are transported to the interstitium
| - use GLUT-2 transporter
27
Where does protein digestion begin?
stomach
28
Describe the beginning of protein digesting in the stomach
- chief cells produce pepsinogen (prohormone)
| - low pH activates pepsinogen to pepsin which releases polypeptides
29
What is the function of the polypeptides released by pepsin in protein absorption?
- enteropeptidase activates trypsinogen to trypsin
- trypsin activates pancreatic carboxypeptidases at SI brush border
- trypsin activates chymotrypsinogen to chymotrypsin
30
What are the structures when peptides are further broken down into "smaller chunks"
oligopeptides
31
What works on the oligopeptides?
brush border enzymes (SI)
32
brush border enzymes from the SI:
- aminopeptidase
- dipeptidase
- tri and di monomers released
33
Describe the physiology of trimer and monomer digestion/absorption
trimer:
-through PepT1 proton cotransporter
-cytosolic preteases release aa
monomer:
-aa-Na cotransporters
-duodenum and jejunum distribution
34
How does infantile protein absorption occur?
by endocytosis d/t immaturity of intestinal mucosa
35
How are nucleic acids digested down after ingesting them?
- into pentose sugars
- nitrogenous bases
- phosphate ions
- all done by nucleases
36
What are the nucleases that digest nucleic acids?
- pancreatic nucleases: RNA and DNA nucleotides
| - intestinal mucosa nucleases
37
what happens to the pentoses and bases during nucleic acid absorption
- pentoses absorbed w/ other sugars
| - bases absorbed by active transport
38
Where does most lipid digestion occur?
duodenum
39
lipid digestion by lipase
- TG digested to 2 FFA + monoglyceride
| - use lingual, gastric and pancreatic lipases
40
What is the function of cholesterol esterase?
-hydrolyze cholesterol esters
41
What does cholesterol esterification do to the cholesterol?
increases hydrophobicity
42
Function of bile salts in terms of lipid digestion/absorption
to emulsify lipid droplets which organizes them into micelles
43
What all lipids can diffuse across the brush border membrane? (4)
- FFA
- monoglycerides
- cholesterol
- fat-soluble vitamins
44
chylomicron
-lipoprotein composed of TG, FFA, chol, and vitamins
45
Where does chylomicron formation occur?
golgi
46
Explain the path of the chylomicron
- extruded from basal membrane
- enters lacteal
- travels vis lymph system to enter venous circulation at the thoracic duct
47
What are the fat soluble vitamins?
- AKED
| - are absorbed w/ lipids
48
Where are water soluble vitamins absorbed?
in the upper SI by diffusion
49
absorption of vitamin B12
-binds to intrinsic factor
which is produced by gastric parietal cells
-absorbed in the ileum
50
absorption of K and B vitamins
- produced by normal flora
| - absorbed in the colon
51
What is the source of electrolytes?
- foods
| - GI secretion
52
cation and anion digestion/absorption
cations:
- Na: cotransported w/ glc and aa
- K: dimple diffusion; absorbed in SI, secreted in LI
anions:
- Cl
- HCO3
- both follow electrochemical gradients
53
What is the cofactor for Ca absoprtion
vitamin D
54
What happens if there is a decrease in blood Ca?
- parathyroid gland secrete parathyroid hormone
- stimulates bone to release Ca
- increases kidney reabsorption of Ca
- increases renal activation of vit. D increasing intestinal absorption
55
What are our sources of iron
- heme iron from hgb and myoglobin (only 10-15% but higher bioavailability)
- non heme iron from cereals, veggies, fruits etc
56
how is iron absorbed?
- ferric reductase enzyme on brush border reduced ferric to Fe2+
- DMT1 transporter actively transports divalent metals into enterocyte
- binds to ferritin = mucosal iron barrier
57
What happens when Fe is needed?
it is absorbed and carried by transferrin
58
What happens when Fe amount is adequate?
it is sloughed off and eliminated
59
How much fluid enters the intestine daily? And what is the breakdown?
about 10 L
- 8 L secreted
- 1-1.5 as saliva
- 2-3 by stomach
- 1 as bile
- 1 as pancreatic secretions
- 2 secreted by SI
60
How much fluid makes it to the colon?
- about 1 L
| - 90% is absorbed across the SI epithelium
61
how much fluid is lost in feces daily?
- about 150 mL
| - the rest is absorbed by colon
62
intestinal absorption of water
- passive process
| - requires movement of solutes
GI 1
flashcards
Decks in class (16)
# Cards
-
Phys 248
-
Phys 362
-
Phys 150
-
Phys 456
-
Patho - GI Neoplasia98
-
Lab Medicine89
-
Clin med: diseases of rectum and anus53
-
Phys Di - Abdominal Exam109
-
Radiology93
-
Pharm - GI Potpourri74
-
Clin Med IBS & Constipation59
-
Clin Med Diverticulosis/litis & Colon Polyps66
-
Pharm - nutrition and the gut28
-
ClinMed- common disorders of intestinal malabsorption37
-
clinmed - c. diff colitis and ischemic bowel dz44
-
EBM Terminology20
