Intestinal Absorption and Secretion Flashcards Preview

Physiology and Neuroscience > Intestinal Absorption and Secretion > Flashcards

Flashcards in Intestinal Absorption and Secretion Deck (65):
1

how many litres is the dietary intake?

1.5L

2

what is the internal secretion formed of and the proportions?

saliva - 1.5L
gastric juice - 3L
pancreatic juice - 2L
bile - 0.5L

3

how many litres is the internal secretion in total?

7L

4

how many litres is the faecal loss?

0.2L

5

how many grams of NaCl have to be retrieved?

7L x 9g/L = 63 g of NaCl

6

are there villi in the colon?

no - just deep pits
500mL presented and 300mL recovered

7

what do crypt cells produce?

cells that migrate along villi in 48 hours

8

when can cells absorb?

when they mature

9

are tip cells mature?

yes - they can absorb

10

what do individual cells on villus have?

brush border with enzymes

11

what is present in the enterocytes

lateral spaces and tight junctions

12

how are the tight junctions at the top of the small intestine (jejunum)

leaky

13

how are the tight junctions at the bottom end of the small intestine (ileum)

tight

14

what do tight junctions allow?

permeability - fluid can enter the cell

15

how much does the surface area expands from simple cylinder

600x

16

how much do the folds of kerckring increase the surface area?

3x

17

how much do the villi increase the surface area?

10x

18

how much do the microvilli increase the surface area?

20x

19

how does this influence absorption

it is assumed to enhance absorption - it may be more for a surface for brush border enzymes

20

what does hydrostatic pressure do?

aid or prevent fluid absorption

21

is there net absorption when pressure is zero?

yes

22

how does the luminal pressure affect the blood pressure

if the luminal pressure increases so does the blood pressure

23

how does the luminal suction pressure affect the fluid absorption

it decreases the absorption rate

24

what does the "standing gradient" explain?

the absorption at zero net pressure - NaCl is pumped into the lateral spaces

25

how many stages are there in the standing gradient

2

26

how does the first stage of the standing gradient work

an increase in the osmotic pressure in the lateral spaces pulls fluid in through paracellular and transcellular routes

27

what happens in the second stage of the standing gradient

an increase in the lateral space hydrostatic pressure pushes fluid into the interstitial space and from there into the capillaries

28

what does the biochemical engine for sodium ion transport consist of?

a serial membrane sited Na/K ATPase pump that pumps sodium ion out of the cell and takes K ion in

29

how is the concentration of sodium within the cell

it is lowered

30

why does the sodium ion diffuses in

because of a diffusion gradient for sodium ion

31

what makes the absorbate close to plasma values

water dilution and lateral space hypertonicity

32

where does some leakage of Na+ into lumen happen

in tight junctions

33

where is the sodium ion from the sodium leakages recycled?

in the jejunum

34

how effective is the absorption of the recycled sodium in the jejunum?

less efficient

35

what makes the water absorption more effective in the ileum

the tight junctions are tight

36

what is linked to the sodium ion gradient

the time it takes the solutes to be absorbed

37

what does a sodium ion-glucose transporter (SGLT1) pulls in the brush border membrane?

a glucose molecule actively into the cell

38

how does the glucose exits the cell?

passively via GLUT2

39

what can glucose force sodium to do?

it can force sodium ion entry

40

what is also absorbed by the route

many amino acids

41

what makes the transporter PEPT pull peptides into the cell?

the proton gradient - pH outside the cell is pH6 through Na/H but inside is pH7.4

42

what kind of ions also facilitate fatty acid absorption?

hydrogen ions - sp3 main foodstuffs absorbed by gradients in ions

43

what does sodium ion gradient energises?

sugar and some amino acid absorption

44

what does hydrogen ion gradient energises

peptides and some amino acid absorption

45

how do fats converted to fatty acids enter the cell?

by associating with H+ ions - protonating

46

what type of transport do some essential minerals undergo

active transport

47

what type of transport do most essential vitamins undergo if they are nor fat soluble

undergo active transport

48

how much liquid can be secreted in an hour by a person infected with cholera?

1L per hour

49

what type of infection is cholera

intestinal affliction

50

what occurs in cholera?

intestinal secretion form the villus cells (enyerocytes) enhanced by enterotoxins

51

what is the normal secretion value per day accepted after 1971

1500mls per day -- without proof

52

what is the fluid circuit hypothesis

separation of secretion and absorption

53

which is the new requirement for new biochemical apparatus

chloride to be transported towards the lumen with Na+ passively following

54

what does NKCC1 do

it is a co-transporter and powers Cl- entry into the cell down the sodium ion gradient

55

what does CTFR protein do?

allows Cl- out into the lumen

56

what is the net effect

Cl- is propelled towards the lumen

57

what does the cholera toxin do?

enhance the propulsion of Cl- towards the lumen and heat stable STa enterotoxin

58

what attaches to intestinal receptors?

STa and cholera toxin (CT)

59

how does STa cause Cl secretion

via cGMP guanylate cyclase

60

how does CT cause Cl secretion

via cAMP adenylate cyclase

61

how does STa influence fluid absorption

it reduces it

62

what should the chloride channel blockers do if the secretion by Cl- channel blockers is ocurring

the chloride blockers should restore fluid absorption - but they don't

63

what does vibrio cholera promote?

the production of large amounts of VIP, a neurotransmitter vasoactive intestinal polypeptide), and Bona Occludens Toxin (ZOT)

64

what is the function of ZOT

keep lateral spaces open

65

how can we prove that fluid absorption or secretion depends on blood pressure i.e. capillary pressure?

using small intestine perfused with zero sodium ion perfusate and a sodium ion transport inhibitor, i.e. a loop that cannot absorb by biochemical means since fluid absorption is inhibited