GIT - Lecture 8 Flashcards
1
Q
What do pancreatic lipases break down?
A
fats
2
Q
Pancreatis lipases break down fats into what kind of molecules?
A
fatty acids, di/monoglycerides
3
Q
Pancreatic lipase can only function under the presence of what enzyme?
A
colipase
4
Q
What does pancreatic pro-colipase react with trypsin to form?
A
colipase
5
Q
In addition to pancreatic lipase, what else breaks down fats into fatty acids and mono/diglycerides?
A
bile salts
6
Q
What organ produces bile salts?
A
liver
7
Q
Which organ is the largest gland of the body?
A
the liver
8
Q
What are the 4 functions of the liver?
A
- storage
- synthesis
- detox
- metabolism
9
Q
What does the liver secrete? From where?
A
bile from hepatic ducts
10
Q
Where does bile travel?
A
in the common bile duct
11
Q
Where is bile released?
A
into the SI at the same location as the pancreatic juice
12
Q
What is the volume of bile produced by the liver every day?
A
0.5-1.0L/day
13
Q
What kind of fluid is bile?
A
isotonic
14
Q
What are the 4 main components of bile and which is the most present?
A
Na+, K+, Cl-, HCO3 (most present)
15
Q
What is the pH of liver bile?
A
7.8-8.2
16
Q
What is the function of the pH of liver bile?
A
it helps neutralize acidic chyme
17
Q
What are the 4 components of liver bile?
A
- bile acids
- bile pigments
- cholesterol
- phospholipids
18
Q
What is the % of solids in liver bile?
A
3%
19
Q
Are there digestive enzymes present in bile?
A
no
20
Q
Bile secretion by the liver is ___.
A
continuous
21
Q
Entrance of bile into duodenum is ___.
A
intermittent
22
Q
What is the volume of bile entering the small intestine?
A
<500-700 mL/day
23
Q
Why is only <500-700 mL of liver bile enter the small intestine rather than the total quantity?
A
because as the spincter of Oddi is closed, the bile salts produced by the liver have nowhere to go so they get stored in the gallbladder
24
Q
How much fluid can the gallbladder hold?
A
50-100 mL
25
What is the % of solids in the gallbladder?
10-20%
26
What kind of pH is found in the gallbladder?
7.0-7.5
27
What is there less of in the gallbladder?
bicarbonate
28
What does the gallbladder do to bile salts?
stores and concentrates them
29
If there aren't enough bile salts, what happens to cholesterol and phospholipids?
they precipitate and cause gallstones
30
Bile salts are synthesized in the liver from ___.
cholesterol
31
What do bile salts facilitate?
digestion, transport, and absorption of FAT by forming water-soluble complexes with the fats
32
What do bile salts facilitate the transport and absorption of?
fat-soluble vitamins (A, D, E, K)
33
What kind of cells are bile salts?
amphipathic
34
Where do the phospholipids of cholesterol burry their hydrophobic portions?
in the non-polar side of the micelle
35
Bile salts help form...
stable emulsions
36
Most bile salt is reabsorbed into which kind of blood?
portal blood
37
How is most bile salt returned to the liver?
via enterohepatic circulation
38
The entire bile salt pool is recirculated several times a day between:
liver -> GIT -> liver
39
What is the positive feedback of bile salts?
they regulate hepatic bile flow
40
The more bile salt returned via portal blood, the ___ the volume of bile secreted
larger
41
What will happen to bile secretion if we removed the ileum?
it will decrease
42
What is the negative feedback of bile salts?
they regulate the synthesis of new bile salts
43
The most bile salt is returned in portal blood, the ___ the amount of new bile salt being synthesized
smaller
44
What will happen to bile salt synthesis if we remove the ileum?
the liver will produce more bile salts
45
Why is cholesterol kept in solution?
because it is insoluble in water
46
If cholesterol precipitates, it may give rise to ___.
gallstones
47
In bile, the solubility of cholesterol increases by how much?
2 x 10^6
48
What are the 2 intra-intestinal functions of bile salts?
1. act as detergents and help form stable emulsions
2. assist in the transport of fat and fat-soluble vitamins from SI -> intestinal cells
49
What is the intracolonic function of bile salts?
they inhibit Na+ transport and H2O absorption
50
Excess of what in the colon causes diarrhea?
bile salt
51
What 2 kinds of cells are found in the pancreas?
- release a large volume of juice rich in HCO3
- release a small volume of juice rich in enzymes
52
The pancreas contains cells that release a large volume of juice rich in ___
HCO3
53
The pancreas contains cells that release a small volume of juice rich in ___
enzymes
54
What are choleretics?
agents which cause the liver to secrete a large volume of bile
55
What are cholagogues?
agents which cause an increase gallbladder emptying
56
What is the Law of Reciprocal Activity?
if the gallbladder is contracted, the Sphincter of Oddi will be relaxed and vice versa
57
Polysaccharides get broken down into disaccharides via what enzymes?
salivary and pancreatic amylase
58
What level polysaccharides need to be broken down in order to be absorbed?
into monosaccharides
59
Proteins get broken down into small peptides via what enzymes?
pepsin, trypsin, chymotrypsin
60
What do proteins need to be broken down into in order to be absorbed?
amino acids, di and tripeptides
61
Fats are broken down into mono, diglycerides and fatty acids via which enzymes?
lipase, co-lipase and bile salts
62
Final steps in digestion are mediated by which kind of enzymes?
intestinal enzymes
63
Where are intestinal enzymes produced?
at the site where absorption will take place
64
What produces intestinal enzymes?
mucosa
65
The small intestine secretes what kind of juice?
intestinal juice
66
What are the 3 components of intestinal juice?
water, mucus, ions
67
What does the small intestine receive to aid digestion?
pancreatic juice enzymes
68
What kind of enzymes does the small intestine contain?
brush border enzymes
69
What are brush border enzymes attached to?
the microvilli of small intestine epithelial cells
70
What does the small intestine do for mechanical digestion?
segmentation
71
What does the small intestine do for chemical digestion?
chyme mixes with pancreatic juice, intestinal juice and bile
72
Where does the absorption of digestion nutrients occur?
in the small intestine
73
What allows for secretion, digestion and absorption in the small intestine?
increased surface area
74
What is the region where the invaginations are in the small intestine?
crypt region
75
What is the region where digestion is completed in the small intestine?
villus region (in the villi)
76
What are the names of the cells found in the villus region that absorb all the nutrients?
enterocytes
77
What do enterocytes have on their surface? Why?
microvilli where they produce the enzymes
78
Crypt cells lack what kind of enzymes?
digestive enzymes
79
What do crypt cells secrete a large volume of?
alkaline fluid (succus entericus)
80
What is the name of the alkaline fluid produced by the crypt cells?
Succus Entericus
81
What kind of fluid is succus entericus?
isotonic
82
What is the pH of the succus entericus?
7.5-9
83
Do villi secrete fluid?
no but they complete digestion and absorb nutrients and fluid
84
Enterocytes in the villi synthesize digestive enzymes which remain where?
in the brush border
85
What is the major enzyme produced by the small intestine?
enterokinase
86
Where are disaccharases produced?
in the brush border
87
What is also happening in the crypt region in addition to the production of Succus Entericous
rapid cell division
88
Where do the cells undergoing rapid cell division in the crypt region do and go?
divide into the cell types that will populate the lumen
89
Why is it important that there is rapid cell division in the crypt region and that it moves to the lumen?
because the cells in the lumen are constantly being damaged by the enzymes and wearing out because of their constant use
90
In the villus, fats are absorbed via the ___.
lacteals
91
What are chylomicrons?
fat and protein complexes absorbed at the level of the lacteal
92
Fats are processed by which system?
the lymphatic system
93
Carbohydrates and sugars return to the liver via the ___ ___ ___.
hepatic portal vein
94
How are carbohydrates and sugars absorbed?
via the capillary
95
What kind of fluid are colonic secretions?
alkaline
96
What ions are both present in the same concentration (100-150 mEq/L) in the colonic secretions?
HCO3 and K+
97
What is there a lot of in colonic secretions?
mucin
98
Are there any digestive enzymes of absorption of nutrients in the colon?
no
99
What kind of activity is there a lot of in the colon?
bacterial activity
100
What reflexes and factors regulate intestinal secretions?
- local enteric reflexes
- vago-vagal reflexes
- hormonal factors
101
How many litres are actually entering the GIT every day?
9 liters
102
What contributes to the 9 L of fluid entering the GIT every day?
2 litres ingested + 7 litres secretes
103
In addition to water, what is also reabsorbed from the lumen of the GIT?
very large quantities of ions
104
How many grams of protein is released into the GIT via secretions?
80 g
105
Most of absorption is ___.
reabsorption
106
What are the sites of exchange characterized by?
1. very large surface area of small intestine
2. intimate contact with blood vessels
107
Which GI organ is essential to life?
small intestine
108
Why is the SI the only GI organ essential to life?
because the colon cannot take over nutrient absorption
109
What kind of blood flow goes to the intestine?
postprandial
110
What is the rate of flow in to intestine?
1-2L/min
111
What does each villus have?
a capillary loop and lacteal
112
What is the lymph flow rate?
1-2 mL/min
113
Where is the major area of absorption of nutrients?
the duodenum
114
What is absorbed mostly at the ileum but it produced in absorbed in small quantities throughout the small intestine?
ileum
115
Where does vitamin B12 only have absorptive sites?
ileum
116
How does absorption take place? (5)
- simple diffusion
- facilitated diffusion
- active transport
- pinocytosis
- osmosis
117
Water always follows the osmotic gradient generated by the movement of ___ and ___.
ions and nutrients
118
What are the requirements for absorption?
- Adequate Digestion
- Adequate Sites for Absorption
- Adequate Transit Time for Absorption
- Adequate Co-factors, Transporters
119
How many litres of water is absorbed by the SI?
7 L
120
How many litres of water is absorbed by the colon?
2 L
121
What is the maximum capacity of absorption of water from the SI?
15 L/day
122
What is the maximum capacity of absorption of water from the colon?
4-5L
123
Is the efficiency of the GIT high or low? Why?
high due to effective coordination of activities within an organ and between organs
124
What is GIT transit time related to?
the functional activities of each organ
