Anuj

Question 1

SI

Answer 1

Folds of Kerching
Microvilli + Crypts of L
Microscopic Microvilli
6m, 200cm2
Absorbs: na, k, cl, h2o, nutrients
Secretes: HCO3-

Question 2

LI

Answer 2

Semilunar folds
crypts
microvilli
2.4cm, 25cm2
Absorbs: na, cl, h2o
Secretes: K+ HCO#-

Question 3

Glucose and a/acid co-transporters

Answer 3

2 active transport
usually on “active” membrane
1. Apical SGLT (2 Na Glucose/a/acid)
2. Basolateral GLUT2

Question 4

Na+ channels dependance

Answer 4

1. Fasting/post prandial state

2. GI region

Question 5

Na/K ATPase blockage

Answer 5

Digitalis drug

Question 6

Paracellular

Answer 6

Tight junctions
Lower resistance
Passive

Question 7

H2o absorption

Answer 7

Jejunum mainly

Question 8

Fluid movement

Answer 8

Fluid movement always coupled by active solute movement

coupled to Solvent drag: dissolved solute swept along with bulk H2O movement (solvent)

Question 9

Na+ movement

Answer 9

1. Na+K+ ATPase
2. Na+/H+ (counteracts acidosis) (secretes H+ for Na+)
3. Parallel Na+/H+ and Cl-/HCO3-
4. Epithelial Na+ (aldosterone dependant, for Na+ retention)
   - Cl- movement is dependant on Na+

Question 10

Cl- movement

Answer 10

1. Passive or Paracellular
2. Cl-/Hco3-
3. Parallel Na+/H+ and Cl-Hco3-

Question 11

K+ movement

Answer 11

BK and IK1

Question 12

CFTR

Answer 12

cystic Fibrosis Transmembrane Receptor
Activated: increased Ca, cAMP and VIP (vasopeptides)
ECF –> ICF –> Lumen
Na follows (homeostasis) + H2O follows (osmolarity)(losing fluid)
=NaCl in lumen

Question 13

Control of Absorption and Secretion

Answer 13

1. Enteric: Ach, VIP(vasopeptides) and other Secretagoges
2. Endocrine: Aldosterone
3. Paracrine: 5HT

Question 14

Diarrohea

Answer 14

> 200ml day/3+ bowel movements
1.5 mil 5 1mil
SI: voluminous (where most reabsorption occurs)
LI: small volume
Osmotic D: mal absorption (increased osmotic load)
Secretory D: increased secretion due to Na and Cl channels

Question 15

Osmotic Diarrohea

Answer 15

macronutrients malabsorption retaining osmotic pressure in the lumen and therefore water is retained
-pancreatic disease (proteases, lipase and amylase),
-large intakes of sugar
alcohols(sorbitol)
- fructose and lactose intolerance
-coeliac disease

Lactose intolerance
• Lack of the enzyme lactase
• 75% world population show some intolerance
- 5% incidence N Europe to > 90% in Africa and Asia

Coeliac disease
Non tropical spruce/ gluten enteropathy
Autoimmune reaction: AB against gluten
destruction of epithelial cells and severe villi blunting
Nutrient malabsorption

Question 16

Secretory Diarhoea

Answer 16

increase active secretion
congenital absence of Cl-HCO 3 exchanger
E. Coli or cholera toxin
bacterial microorganisms produce enterotoxins which raise intracellular [cAMP], [cGMP] or [Ca+2]
stimulation of anion secretion, especially Cl- (via CFTR).
Na+ too (To maintain lumenal charge balance) , along with water
Does not impact on nutrient coupled Na absorption, ORS (Oral Rehydration Therapy) containing glucose and Na+ is an effective treatment for secretory diarrhea

Question 17

Case Study

Answer 17

The ambulance was called in and the paramedics who attended to Sandy recorded a low BP and extremely high HR (trying to maintain her BP).
As all her ECF fluid was being lost her skin was dry and indicated dehydration.
Microscopic examination of the patient’s stool reveals the presence of a large number of Vibrio cholera bacteria. Increase Cl- secretion > increase Na+ secretion > Water loss
Losing fluid from ECF. (less ECF > less plasma > less blood flow > less BP > increased HR)
She has Secretory Diarrhoea
Treated with ORT

Question 18

ORT

Answer 18

Oral Rehydration Therapy
Reduced mortality by 60%. 500 million ORS sachets per year.
• glucose, bicarbonates, ions.
Cholera only impacts the Cl- channels, not the Na+/glucose co-transporters.
Na+ and glucose moved into the cell, Cl- follows into the cell also. Effectively nutrients lost are brought back in.
•Bicarbonates are to counteract the acidotic effect of diarrhea, maintaining pH
o To correct the loss of electrolytes from the body
o To restore fluid loss from the body
o To restore Na+ balance across the brush border to maintain the transport mechanism
o To aid osmotic reabsorption in the lumen