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Digestion And Absorbtion Flashcards

1
Q

Functions of intestinal epithelial barrier

A

Absorption of nutrients,

Control pathogen/toxin passage

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2
Q

Why does the ieb need to be permeable

A

Absorption of nutrients

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3
Q

Why does the ieb need to be impermeable

A

Control passage of pathogens/toxins

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4
Q

What is modulates regulation of ieb

A

Outer micro environment,

Inner microenvironment

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5
Q

What forms the specialised structures of enterocytes

A

Specialised cytoskeletal proteins

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6
Q

Function of enterocyte brush border

A

Increase apical surface area

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7
Q

Purpose of tight junctions between enterocytes

A

Prevent passage of toxins and pathogens

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8
Q

Which has a higher SA - skin or gut mucosa

A

Gut mucosae

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9
Q

Which organ does 95% of nutrient absorption occur in

A

Small intestine

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10
Q

Inputs of fluid to digestive system

A

Ingested water,
Liver and pancreatic secretions,
Salivary gland secretions,
Glands in stomach and small intestine secretions

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11
Q

Outputs of fluid from digestive system

A

Small intestines - major
Colon
Feces

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12
Q

What are intestine crypts

A

Invaginations in epithelium around vili

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13
Q

Cells in crypts

A

Panettone cells,

Stem cells

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14
Q

Why do crypts contain stem cells

A

Produce epithelial, goblet, and enterocyte cells

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15
Q

What is the intestinal clinal conveyor belt

A

Stem cells in crypts produce new cells -> cells pushed up vili -> cells at top of vili extruded and die

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16
Q

Advantages of extruding cells at top of vili

A

Dead cells nourish micro biome bacteria,

Prevents cells acquiring mutations

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17
Q

Which molecules are absorbed in the duodenum

A

Amino acids,

Iron

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18
Q

Where are triglycerides, proteins, and carbohydrates broken down

A

Duodenum

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19
Q

What molecules are absorbed in the jejenum

A 
Iron,
Monosaccharides,
Calcium,
Folate,
Fat soluble vitamins,
Free fatty acids,
Monoglycerides,
B12,
Water,
Sodium
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20
Q

What molecules are absorbed in the ileum

A

Water,
B12,
Intrinsic factor,
Bile acids

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21
Q

Which molecules are absorbed in the colon

A

Water,
Electrolytes,
Bile acids,

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22
Q

Phases of digestion and absorption

A

Luminal,
Mucosal,
Post absorptive

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23
Q

What happens in the luminal phase of digestion and absorption

A

Ingested food broken down

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24
Q

What dreams down food in luminal phase

A

Acid in stomach,
Alkali in small intestine,
Enzymes from pancreas and gastric+small intestine mucosa

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25
What happens in the mucosal phase of digestion and absorption
Nutrients enter intestinal cells
26
How do nutrients enter intestinal cells in mucosal phase
Selectively taken up at enterocyte brush border then enter intestinal cells
27
What happens in the post absorptive phase of digestion and absorption
Absorbed nutrients transported to rest of body
28
How are absorbed nutrients transported in post absorptive phase
Lymphatics, | Portal blood circulation
29
Water use in digestive system
Hydrolysis, Facilitate absorption, Facilitate propulsion of gut contents, Combination w mucin granules to make mucus
30
What happens to carbohydrates and complex carbohydrates in the luminal phase
Split into disaccharides and limit dextrins by salivary and pancreatic enzymes
31
Are pancreatic or salivary enzymes more important in breakdown of carbohydrates
Pancreatic
32
What happens to carbohydrates and complex carbohydrates in the mucosal phase
Brush border enzymes complete digestion to monosaccharides which enter epithelial cells
33
Brush border enzymes
``` Sucrase, Lactase, Maltase, Limit dextrinase, Glucoamylase ```
34
How do glucose and galactose enter epithelial cells in the mucosal phase of digestion and absorption
Sodium linked secondary active transport across apical membrane
35
How does fructose enter epithelial cells in the mucosal phase of digestion and absorption
Facilitated diffusion
36
What happens to carbohydrates and complex carbohydrates in the post absorptive phase
Sugars transported to portal vein
37
How do sugars enter the portal vein in the post absorptive phase of digestion and absorption
Facilitated diffusion across basolateral membrane
38
What happens to lipids in the luminal phase
Lingual lipases act in mouth and gastric lipase in stomach, | Pacreatic lipase digests triglycerides to free fatty acids and monoglycerides
39
What helps pancreatic lipase digest triglycerides
Bile salts
40
What do micelles contain
Fat soluble vitamins and cholesterol
41
What do bile salts do
Fat globule Emulsification to enable lipase action
42
What happens to bile salts
Absorbed in ileum -> recycled in liver
43
Why does disease of the ileum cause issues digesting fats
Bile salts can’t be reabsorbed and recycled
44
What happens if bile salts aren’t reabsorbed
Go to colon -> exert osmotic pull -> diarrhoea
45
How do commensalism bacteria regulate digestion
Deconjugate primary bile acids to secondary bile acids
46
Why do commensalism bacteria deconjugate bile acids
To stop themselves being digested
47
What molecule is the backbone of bile acids
Cholesterol
48
How does the liver produce primary bile acids
Conjugates cholesterol w amino acids
49
Which type of bile acids are most effective
Primary
50
Effect of too many commensal bacteria
Lots of less effective sec bile acids creates -> hard to digest fats
51
Why are conjugated bile acids more efficient than unconjugated
Become more ionised at intestinal pH
52
What happens to lipids in the mucosal phase
Fatty acids and monoglycerides enter enterocytes, are reassembled to triglycerides, and packaged into chylomicrons
53
How do fatty acids and monoglycerides enter enterocytes
Simple diffusion
54
What organelle packages triglycerides into chylomicrons
Golgi apparatus
55
What happens to lipids in the post absorptive phase
Chylomicrons exocytosed across basolateral membrane and enter lymphatic capillaries
56
Why do chylomicrons enter lymphatic capillaries
Too big to enter capillaries
57
Where does lymphatic fluid carry chylomicrons too in the post absorptive phase
Blood
58
What happens to proteins in the luminal phase
Pepsin acts in stomach and other enzymes secreted by pancreas act in s intestine
59
What is the zymogen of pepsin and what is it activated by
Pepsinogen, HCl
60
What cells release pepsinogen
Chief cells
61
Which cells release HCl in the stomach
Parietal cells in gastric pits
62
What happens to proteins in the mucosal phase
Trypsinogen converted to trypsin which activates chymotrypsinogen and procarboxypeptidase, A acids enter epithelial cells,
63
Which brush border enzyme converts trypsinogen to trypsin
Enterokinase
64
What is chymotrypsynogen activated to by trypsin
Chymotrypsin
65
What is procarboxypeptidase activated to by enterokinase
Carboxypeptidase
66
How do amino acids enter epithelial cells in the mucosal phase
Sodium linked secondary active transport across apical membrane
67
Why are zymogens inactive when no protein needs digesting
To prevent digesting self
68
What happens to proteins in the post absorptive phase
Amino acids transported across basolateral membrane
69
How are amino acids transported across the basolateral membrane in the post absorptive phase
Facilitated diffusion
70
Can vitamins be created by the body
No
71
Which vitamins are fat soluble
A D E K
72
How are fat soluble vitamins absorbed
With lipids into lymph - | Dissolve in lipids droplets, micelles, chylomicrons
73
Which vitamins are water soluble
B C
74
How are most water soluble vitamins absorbed
Follow water from gut lumen through mucosa
75
How is B12 absorbed
Binds to haptocorrin -> complexed w stomach derived intrinsic factor -> absorbed in ileum -> transported to portal circulation -> transferred to transcobalamin ii (plasma transporter) -> absorbed in terminal ileum
76
How is B12 normally taken into body
Bound to dietary protein
77
What is the function of transcobalamin ii in absorption of B12
Plasma transporter
78
Causes of generalised malabsorption
``` Small intestine disease, Pancreatic disease, Conditions in other organs, Acute infection, Chronic infection ```
79
What do small intestinal mucosal diseases cause
Reduced absorptive area | Malabsorption in mucosal phase
80
Small intestinal mucosal diseases
Celiac, Post infectious malabsorption, Crohn’s
81
Cause of coeliac disease
Vili destroyed by immune response
82
Effect of coeliac disease
Malabsorption, Villous atrophy, Crypt hyperplasia, Increased IELs
83
Which isoforms of the human leukocyte antigen protein cause coeliac - HLA DQ
DQ2 DQ8
84
What do the DQ2 and DQ8 human leukocyte antigen protein code for
Arm on APC that presents gliadin to CD4 T cells
85
What part of gluten triggers an immune reaction in coeliac
Gliadin
86
What is the human leukocyte antigen
Major histocompatibility complex in humans
87
Main cause of generalised malabsorption in economically developed world
Coeliac
88
Main cause of generalised malabsorption in developing world
``` Acute/chronic infection - viral infection - chronic bacterial infection of upper GI tract Post infectious malabsorption Tropical sprue ```
89
What is specific malabsorption
Failure of processes governing absorption of 1 class/type of nutrient
90
What enzyme is the majority of the worlds population deficient in
Lactase
91
What causes phase of disaccharide absorption is affected by lactase deficiencies
mucosal
92
What gene is mutated in lactase deficiency
SLC5A1
93
What does the SLC5A1 gene encode
Member of the SGLT1
94
What does SLC5A1 mutation cause
Glucose galactose malabsorption
95
Effects of lactase deficiency
Disaccharides reach colon -> add to osmotic load -> watery diarrhoea, Sugars ferment in intestine -> gaseous distension + watery diarrhoea

Met1 (8 decks)

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