Lecture 27: Absorption

Question 1

What is absorption?

Answer 1

The passage of substances from the GI lumen across the lining of the intestine into the interstitial fluid and then into the blood or lymph

Question 2

What are the sties of absorption?

5

Answer 2

• Mouth
• Oesophagus
• Stomach
• Small intestine
• Large intestine

Question 3

What does the correct rate of propulsion allow?

2

Answer 3

• Digestion

- Absorption

Question 4

What does the correct rate of motility ensure?

Answer 4

Exposure of products of digestion to absorptive surface

Question 5

What is rate of absorption proportional to?

Answer 5

Surface area

Question 6

What happens when the surface area of absorption is greater?

Answer 6

The rate of absorption increases

Question 7

What are anatomical adaptations that maximise surface area?

4

Answer 7

• Length of intestine
• Circular folds
• Villi
• Microvilli

Question 8

What is the lumen of the intestine continuous with?

Answer 8

The outside world

Question 9

What is a barrier between the underlying components of the intestinal lumen and the environment?

Answer 9

The intestinal epithelium

Question 10

What are the 2 pathways across the epithelium barrier?

Answer 10

• Paracellular

- Transcellular

Question 11

What is the paracellular pathway across the epithelium?

Answer 11

A gap between the cells

Question 12

What is the cellular pathway across the epithelium?

Answer 12

Across the cell membranes through the cytoplasm

Question 13

What do solutes not do?

Answer 13

Cross cell membranes

Question 14

What is the only barrier for solutes using paracellular pathways?

Answer 14

Tight junctions binding cells together

Question 15

Paracellular pathways are relatively what?

Answer 15

Non-selective

Question 16

If a solute is relatively what? it can get across a paracellular pathway

Answer 16

Small

Question 17

What does movement through a paracellular pathway require?

Answer 17

A concentration gradient

Question 18

Using a cellular pathway what must solutes cross?

Answer 18

Two cell membranes

Question 19

What are cell membranes?

Answer 19

Lipid bilayers

Question 20

If a solute is not lipid soluble what does it require for the cellular pathway?

Answer 20

A transport protein

Question 21

To maximise the absorption across available surface area nutrients are reduced to what?

Answer 21

Their smallest possible unit

Question 22

What do specific transport proteins do?

Answer 22

Absorb what is required

Question 23

What do specific transport proteins allow?

Answer 23

Active transport against a concentration gradient

Question 24

What is there a large blood flow to?

Answer 24

The intestine

Question 25

What do the arrangement of blood vessels and lacteal in villi prevent?

Answer 25

The build up in interstitial fluid

Question 26

What is the mechanism of water absorption?

Answer 26

Osmosis

Question 27

What is osmosis?

Answer 27

Passive movement of water from lumen into blood

Question 28

How is the osmotic gradient set up?

Answer 28

By the absorption of salts and nutrients

Question 29

How is sodium absorbed? | 2

Answer 29

- Passive movement via paracellular pathways | - Active transport via cells

Question 30

Active transport of sodium across cell membranes can use what mechanisms? (3)

Answer 30

- sodium transport alone - sodium transport coupled to monosaccharides - sodium transport coupled to amino acids

Question 31

When moving alone what does sodium move down?

Answer 31

Its concentration gradient

Question 32

When moving alone what does sodium move through?

Answer 32

Transport proteins

Question 33

When moving out of a cell what does sodium need to move from and to?

Answer 33

From a low concentration to a high concentration

Question 34

What does sodium use to move out of a cell?

Answer 34

ATP

Question 35

How are carbohydrates absorbed?

Answer 35

Active absorption/Cotransport with sodium via cellular pathway

Question 36

What are carbohydrates absorbed as?

Answer 36

Monosaccharides

Question 37

How are proteins absorbed?

Answer 37

By passive or active absorption

Question 38

When moving passively what do amino acids move down?

Answer 38

Concentration gradient via paracellular pathways

Question 39

What are Di- and tri- peptides absorbed via?

Answer 39

via H+ dependant cotransport

Question 40

What are amino acids absorbed via?

Answer 40

Via sodium dependent cotransport

Question 41

Are products of fat digestion lipid-soluble?

Answer 41

Yes

Question 42

What can lipid soluble products diffuse across?

Answer 42

The cell membrane

Question 43

How are lipid soluble products delivered to the brush border?

Answer 43

Micelles

Question 44

In the cell what are products of fat resynthesised into?

Answer 44

Triglyerides

Question 45

What do products of fats in the cell get packaged into?

Answer 45

Chylomicrons

Question 46

What do chylomicrons exit the cell by?

Answer 46

Exocytosis

Question 47

What do chylomicrons enter?

Answer 47

The lacteals

Question 48

what happens to bile salts in micelles?

Answer 48

They are eventually absorbed

Question 49

Where are bile salts from micelles absorbed?

Answer 49

Ileum

Question 50

When are bile salts from micelles absorbed?

Answer 50

After fat absorption is complete

Question 51

How are bile salts absorbed in the colon?

Answer 51

by passive absorption

Question 52

What are the 2 classes of vitamin?

Answer 52

- Fat soluble | - Water soluble

Question 53

What are 4 fat soluble vitamins?

Answer 53

vitamin A, D, E, K

Question 54

What are fat soluble vitamin absorbed with?

Answer 54

Fats

Question 55

What are water soluble vitamins? | 2

Answer 55

- Sodium | - Vitamin C

Question 56

Where are faeces formed?

Answer 56

Large intestine