Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Metabolism > Digestion and Absorption > Flashcards

Digestion and Absorption Flashcards

1
Q

what is the role of the intestinal epithelium barrier

A
  1. Enable the absorption of nutrients

2. Control the passage of pathogens or toxins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how is the internal epithelial barrier regulated

A
  • Outer microenvironment by the microflora and chyme

- Inner microenvironment by immune cells, fibroblasts or the enteric nervous system and extrinsic nerve fibres)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the functional structure of the enterocytes built by

A

specialised cytoskeletal proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how much absorption of nutrients occurs In the small intestine

A
  • 95% of absorption of nutrients occurs in the small intestine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the rate of fluid movement in the digestive system

A
  • ingested water (2 liters)
  • liver and pancreatic secretions ( 2 liters)
  • salivary gland secretions (1.5 liters)
  • secretions by glands of the stomach and small intestines (3.5 liters).
  • Small intestine absorbs 8.5L
  • Colon 400ml
  • Faeces 100ml
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe what the role of the stem cells at the bottom of the crypt is

A

At the base of crypt you have stem cells, replicate all the time, gut is a harsh environment and many of the cells at the top of the crypt is removed therefore the stem cells produced replace them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are the 3 processes of digestion and absorption

A
  1. luminal
  2. mucosal phase
  3. post absorptive phase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

describe the luminal phase

A

The ingested food is broken down by acid in the stomach, alkali in the small intestine and substrate-specific enzymes secreted by the gastric and small bowel mucosa and the pancreas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe the mucosal phase

A

is when pre-digested nutrients are selectively taken up at the brush border membrane of the enterocytes and then enter the intestinal cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

describe the post absorptive phase

A

transport of absorbed nutrients via lympathetics and the portal circulation to the rest of the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why is water needed in the digestive system

A
  • Hydrolysis reactions of digestion
  • Facilitation of absorption (brings products of digestion into close proximity to microvilli)
  • Facilitation of propulsion of gut contents
  • Combination with mucin granules to make mucus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how do crypt cells assure that water will be in the gut (very important)

A
  • Sodium and potassium and chlorine enter by cotransport
  • Chloride enters lumen through CFTR channel
  • Sodium is reabsorbed
  • Negative CL- in lumen attracts sodium by paracellular pathway
  • Water follows
  • This is the system by which the crypt cells assure that water will be in the gut
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what nutrients are absorbed in the small intestine

A
  • Carbohydrate and complex carbohydrates
  • Lipids
  • Proteins
  • Vitamins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is carbohydrates digested and absorbed

A
  1. Luminal phase
    – Split into shorter molecules by salivary (trivial – this is because as soon as you swallow it is inactivated ) and pancreatic (important) enzymes (e.g. maltase, amylase). The amlayse in the salvia does not work at low pH
    = disaccharides + limit dextrins
  2. Mucosal phase
    - brush border enzymes complete digestion.
    - Glucose and galactose enter epithelial cells via sodium-linked secondary active transport across the apical membrane. Fructose enters by facilitated diffusion.
  3. Post absorptive phase – the sugar exits the cells across the basolateral membrane by facilitated diffusion to the portal vein
    Potassium enters and sodium leaves
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the brush border enzymes

A

Sucrase

  • lactase
  • maltase
  • limit dextrinase
  • glucoamylase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe the digestion and absorption of lipids

A
  1. Luminal phase
    - Lipid digestion begins in the mouth with lingual lipases and continues in the stomach where gastric lipase is added to the mixture.
    - With the help of Bile salts, pancreatic lipase digests triglycerides into free fatty acids, and monoglycerides.
  2. Mucosal phase
    - Fatty acids and monoglycerides enter the enterocytes by simple diffusion as the membrane is lipid too
    - Inside the enterocytes the molecules are reassembled into triglycerides and are packaged into large particles called chylomicrons.
  3. Post absorptive
    - The chylomicrons are secreted across the basolateral membrane by exocytosis. - The chylomicrons enter lymphatic capillaries. The flow of lymphatic fluid then carries the chylomicrons to the bloodstream.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what do micelles contain

A

fat soluble vitamins and cholesterol

18
Q

what do bile salts do

A
  • Bile salts enhance the digestive action of liases by breaking down fat globules into smaller droplets
  • emulsification,
19
Q

how are bile salts recycled

A
  • they are absorbed in the ileum and recycled by the liver
20
Q

what are communal bacteria

A
  • they form the microbiome
  • regulates of digestion
  • participate in the synthesis of bile salts
21
Q

biles salts derived from…

A

commensal bacteria are directly linked to both diet and digestion and can be considered to be diet-dependent microbial products

22
Q

what is more efficient in emulsifying fats and why

A

Conjugated bile acids are more efficient in emulsifying fats because at intestinal pH they become more ionized that the unconjugated bile acids

23
Q

what do microbial enzymes do

A

deconjugate bile acids

24
Q

describe the digestion and absorption of proteins

A
  1. Luminal phase
    Begins in the stomach with the action of pepsin. Pepsin is converted from pepsinogen by other pepsin molecules that are activated by HCl secreted by parietal cells.
    Protein digestion is completed in the small intestines by enzymes secreted by the pancreas.
  2. Mucosal phase
    - Trypsinogen is converted into trypsin by enterokinase, a brush border enzyme.
    - Trypsin can then activate:
    - chymotrypsinogen -> chymotrypsin
    - procarboxypeptidase -> carboxypeptidase
    - need to have these proenzymes so it acts as a control mechanism to prevent digesting itself and the gut
    - amino acids enter the epithelia cells via sodium linked secondary active transport across the apical membrane
  3. post absorptive phase
    - amino acids are then transporterd across the basolateral membrane by facilitated diffusion
25
Q

what are the two types of vitamins

A

fat soluble

water soluble

26
Q

describe how fat soluble vitamins are absorbed

A
  • absorbed with lipids as they readily dissolve in lipid droplets, micelles and chylomicrons
  • INTO LYMPH FLUID
27
Q

describe how water soluble vitamins are absorbed

A
  • most water soluble vitamins B,C follow the flux of water from the gut lumen through the mucosa
28
Q

what type of vitamin is B12

A

water soluble

29
Q

describe how B12 is absorbed in the terminal ileum

A
  • binds to haptocorrin which is produced in the salivary glands
    • Must be complexed with stomach-derived intrinsic factor (IF).
  • Transported into the portal circulation.
  • The vitamin is then transferred to transcobalamin II (TC-II/B12), which serves as the plasma transporter
  • Absorbed in the terminal ileum.
  • 60-80% IS INGESTED IN FEACES
30
Q

what circulations do the fat soluble and water soluble vitamins go in

A

fat soluble - lymph fluid

water soluble - portal vein

31
Q

describe how vibrio cholera causes secretory diarrhoea

A
  • Gram negative comma shaped bacterium
  • Alpha part of the chloera toxin binds to adenylate cyclase
  • Activates adenylase cyclase
  • Makes cAMP
  • This activates the CFTR receptor and causes chlorine to go into the lumen
  • Therefore, sodium is excreted to maintain electroneutrality through the paracellular pathway therefore water follow
  • Consistent pour of water into the lumen this is called secretory diarrhoea
32
Q

how do you treat cholera

A

Oral rehydration

  • Drink that contains sodium, glucose and amino acids
  • The sodium glucose and sodium amino acid receptors are not effected by cAMP
  • The pump pumps the sodium out as you don’t want sodium in the cell and it is pumped out into the extracellular fluid
  • Therefore water follows into the extracellular fluid
33
Q

what causes generalised malabsorption

A
  • commonly results from small intestine

- can also result from pancreatic disease or conditions in other organs such as liver disease

34
Q

what does small intestinal mucosal disease cause

A

reduced absorptive area

35
Q

what are examples of small intestinal mucosal disease

A
  • coeliac disease
  • post infections malabsorption
  • crohns disease
36
Q

what is the most common cause of malabsorption in the economically developed world

A

coeliac disease

37
Q

what causes malabsorption in the developing world

A
  • actue or chornic infection
  • post infectious malabsorption and tropical sprue
  • may be initiated by a viral infection
  • may be associated with chronic bacterial infection of the upper gastrointestinal tract.
38
Q

what is specific malabsorption

A

specific malabsorption is the failure of the processes governing absorption of one class or type of nutrient.

39
Q

what is an example of specific malabsorption

A
  • For example genetic or acquired failure to absorb dissachride sugars or vitamin B12
40
Q

disaccharide deficiencies are …

A

generally genetic and most of the world’s population is lactase deficient

41
Q

describe how disaccharide deficiency is caused

A
  • Mutation in the gene LCT: Affecting the ‘mucosal phase’ of dissacharides absorption (lactase is in the brush border).
  • Glucose cannot be converted to galactose
  • Mutation in the gene LCT:
  • Mutation in the gene SLC5A1:
  • SLC5A1 encodes a member of the sodium-dependent glucose transporter SGLT1 (Sodium dependent GLucose Transporter one). Mutations in SLC5A1 cause Glucose-galactose malabsorption.
42
Q

what is the consequences of disaccharide deficiency

A
  • Unabsorbed disaccharides reaching the colon adds to the osmotic load and causes watery diarrhoea.
  • Fermentation of sugars in the intestine causes gaseous distension and adds to the watery diarrhoea. Produces osmotic diarrhea

Metabolism (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions