18 Intestinal Fluid and Electrolyte Secretion and Absorption Flashcards
These are semi-long cards, but it’s sheer memorization, and I spent a lot of time condensing/organizing the info for you :)
Each card will list gut location, then the key characteristics of each absorption method.
What are the 4 sodium absorption methods?
- Na/Glu symport (electrogenic)
- Na/H antiport
- Na/H with Cl/HCO3 antiport (electroneutral)
- Na electrogenic absorption
2 Characteristics of Na/H antiport?
- jejunum more than duodenum
- Stimulated by alkaline lumen (due to pancreatic HCO3 w/ meals)
4 Characteristics of Na/H, CL/HCO3 antiport (electroneutral)?
- ileum & proximal colon
- Primary Na absorption mech. between meals
- Regulated by intracellular pH
- Down due to cAMP, cGMP, Ca++
4 Characteristics of electrogenic Na absorption?
- Distal colon
- ENaC
- Up due to aldonsterone, mineralocorticoids
- Driven by Na/K ATPase
3 Characteristics of Na/Glu symport?
- jejunum more than ileum
- Driven by Na/K ATPase
- Primary mech. for Na absorption when glucose present.
What are the 4 Cl absorption/secretion methods?
- Cl passive (voltage dependent)
- CL/HCO3 electroneutral
- Na/H, CL/HCO3 electroneutral
- Cl secretion
1 Characteristic of Cl/HCO3 (electroneutral) absorption?
-ileum and colon
3 Characteristics of Cl passive (voltage-dependent) absorption?
- jejunum most, ileum & distal colon
- Follows Na (linked to electrogenic Na absorption)
- Can be para or transcellular
What’s special about Na/H, Cl/HCO3 electroneutral Cl absorption?
It’s the same as Electroneutral Na/H, Cl/HCO3 absorption!
4 Characteristics of Cl secretion?
- jejunum, ileum, colon
- Normally lower than absorption, but when massive->diarrhea
- Occurs in crypts
- Secretagogues stimulate this
What are the 4 K absorption/secretion methods?
- Paracellular solvent drag absorption
- Absorption by K/H ATPase
- Passive (electrogenic) secretion paracellularly
- Active K secretion
1 characteristic of paracellular K absorption?
duodenum, jejunum, ileum
3 characteristics of K/H ATPase K absorption?
- Distal colon
- Only occurs in K depleted state
- Dif than gastric H/K antiporter
3 Characteristics of passive K secretion (paracellular)?
- Distal colon
- Compensates for Na electrogenic absorption
- Primary mech. of colon K secretion
3 Characteristics of Active K secretion?
- colon
- Boosted by Na/K ATPase
- Induced by cAMP & aldosterone
What is the major secretagogue that drives Cl secretion?
ACh (acts on ENS)
Lamina propria immune cells make 3 secretagogues. What are they?
histamine (mast cells), prostaglandins (macrophages), eicosanoids (neutrophils, fibroblasts)
Exotoxin secretagogues are made by what 2 bacteria we should know?
E. coli, cholera
Laxatives are what?
secretagogues
What effect on ion transport do ALL secretagogues have?
inhibit NaCl absorption, increase Cl secretion
What are the 3 products that are upregulated as a mechanism
of secretagogue action?
-Up cAMP, Ca++, cGMP
What are the 3 absorptagogues?
mineralocorticoids, glucocorticoids, somatostatin
How do mineralocorticoids work on intestines?
Up Na absorption, K secretion in colon only
