2.Water and electrolyte absorption and secretion in the gastrointestinal tract

Question 1

Surface of small intestine is amplified (folded) at 3 levels

Answer 1

• Folds of Kerchring
• Microvilli and crypts of Lieberkuhn
• Submicroscopic microvilli

Question 2

Surface of Large intestine is amplified (folded) at 3 levels

Answer 2

• Semiluminar folds
• Crypts, but no villi
• Microvilli

Question 3

Absorption of the _______nutrients occurs mainly in small intestine, whereas both the small and large intestine absorb _____ and ______

Answer 3

non-electrolyte

water and electrolytes (Na+, Cl-etc)

Question 4

he small intestine absorbs net amounts of water, Na+, Cl-and K+and secretes ___
whereas the large intestine absorbs net amounts of water, Na+, Cl-and secretes both _________

Answer 4

HCO3-,

K+and HCO3-

Question 5

Absorption of water entirely by osmosis, Coupled tosolute movement.
Occurs via _________ or _______ routes. ________ route is dominant

Answer 5

transcellular or paracellular routes

Paracellular

Question 6

Absorption of water primarily in the?

Answer 6

jejunum

Question 7

______ responsible for considerable Na+ and urea absorption in jejunum

Answer 7

‘Solvent drag’

Question 8

Na+absorption occurs in

Answer 8

villus epithelial cells of the small intestine and surface epithelial cells of the large intestine

Question 9

Na+absorption Maintains a low _______ Na concentration

Answer 9

intracellular

Question 10

Na+absorption Provides force for Na movement from diffusion from _____ across_______

Answer 10

lumen across apical membrane•

Question 11

______transport mediated by Na+ coupled transporters (e.g. Na/glucose transporters) or Na+ channels

Answer 11

Apical

Question 12

Cl-absorption Closely linked to ?

Answer 12

Na+absorption

Question 13

Cl-absorption Active generally involves ?

Answer 13

Cl-HCO3 transporter.

Question 14

In voltage-dependent Cl-absorption, Cl-may passively diffuse from lumen to blood across the _____junctions, driven by the lumen-negative transepithelial voltage (paracellular route). Alternatively, Cl-may diffuse through?

Answer 14

tight

apical and basolateral Cl-channels.

Question 15

, In the absence of a parallel Na-H exchanger, electroneutral Cl-HCO3 exchange at the apical membrane results in?

Answer 15

Cl-absorption and secretion.

Question 16

In the absence of a parallel Na-H exchanger, electroneutral Cl-HCO3 exchange at the apical membrane results in?

Answer 16

Cl-absorption and secretion.

Question 17

The small intestine is a net absorber of??

Answer 17

water
Na+
l-
K+

Question 18

The small intestine is a net secreter of?

Answer 18

Bicarbonates.

Question 19

The human colon carries out net absorption of water, Na, Cl but it carries out net secretion of??

Answer 19

K+ and Bicarbonates

Question 20

Fluid movement is always coupled to

Answer 20

active solute movement

Question 21

solute movement may be coupled to Fluid movement by?

Answer 21

Solvent drag

A phenomenon in which the dissolved solute is swept along by bulk movement of solvent (water)

Question 22

diarrhoea

Answer 22

Dysfunction of fluid absorption in the gi

definition: >200g/day faeces

Question 23

•Osmotic diarrhoea:

Answer 23

results from disturbances of absorption

Question 24

•Secretory diarrhoea:

Answer 24

results from disturbances in secretion

Question 25

diarrhoea Small intestinal origin results in

Answer 25

voluminous diarrhoea

Question 26

diarrhoea large intestinal origin results in

Answer 26

small volume diarrhoea

Question 27

Osmotic diarrhoea Generally caused by

Answer 27

macronutrients malabsorption retaining osmotic pressure in the lumen and therefore water is retained

Question 28

Examples of Osmotic diarrhoea

Answer 28

pancreatic disease (proteases, lipase and amylase), large intakes of sugar alcohols such as sorbitol , fructose intolerance, lactose intolerance, coeliac disease

Question 29

Lactose intolerance

Answer 29

* Lack of the enzyme lactase in adulthood * 75% world population show some intolerance with 5% incidencerate in northern Europe to > 90% in part of Africa and Asia

Question 30

Coeliac disease

Answer 30

* Also called non tropical spruce, or gluten enteropathy * Autoimmune reaction to gluten * Results in destruction of the epithelial cells and if sever blunting of the villi * Nutrient malabsorption

Question 31

Secretory diarrhoea.most common cause of this type of diarrhoea is

Answer 31

a exposure to the E. Coli or cholera toxin. | Enterotoxins produced by the bacterial microorganisms raise intracellular [cAMP], [cGMP] or [Ca+2]

Question 32

Secretory diarrhoea. leads to stimulation of | Also congenital absence of?

Answer 32

anion secretion, especially Cl-. To maintain a charge balance in the lumen Na+ is carried with it, along with water of Cl-HCO3exchanger

Question 33

Secretory diarrhoea does not have an impact on __________________,

Answer 33

nutrient coupled Na absorption

Question 34

ORS containing _________________is an effective treatment for secretory diarrhoea

Answer 34

glucose and Na+