Lecture 7.A. - Water and Electrolyte Absorption Flashcards
Electrolyte and water absorption is mainly under _____ control –> the immediate environment regulates these processes.
Local
How do Paracellular permeability and Trancellular permeability change moving from the Small intestine to the large intestine?
Paracellular is highest in the proximal small intestine and decreases moving to the large intestine.
The opposite is true for Transcellular.
In the duodenum, the contents of the lumen are usually ______ (hypo-, hyper-, or isotonic?). What does this mean for net fluid flow?
Hypertonic
This means net fluid flow from the body into the Lumen of the duodenum.
Patients who have undergone gastric bypass surgery are at risk for ______ syndrome, which is caused by highly hypertonic fluid flowing into the duodenum very quickly (being that the patient has only a small stomach pouch left after the surgery) –> fluid floods into the lumen from the body, causing duodenal swelling. Look for patients to exhibit elevated ____ ____, sweating, nausea, and vomiting/diarrhea.
Dumping Syndrome
elevated Heart Rate
The HCO3-/Cl- Exchanger on the Apical side of Duodenal Villus cells is called either _____ (Downregulated in _______) or _____ (Congenital _____ _____). Remember that H+ is transported across the basolateral side of these cells via the _____ exchanger.
DRA (Downregulated in Adenoma)
CLD (Congenital Chloride Diarrhea)
Na+/H+ Exchanger (NHE1)
How do NHE transporters differ in the Jejunum + Ileum vs in the Duodenum?
In the Jejunum and Ileum they are located on the Apical side, bringing Na+ into the cytosol and moving H+ into the Lumen. In the Duodenum, this exchange occurs on the Basolateral side of the cell.
Bc the Jejunum and Ileum generate a Positive ion gradient on the Basolateral side via the _______, Cl- is absorbed via _______ transport.
Na+/K+ ATPase
Paracellular
The process of WATER absorption in the Jejunum, Ileum, Gallbladder, and the Colon is the same. How does it work?
Ions are transported into the cells on the Apical side, pumped into spaces between the cells creating a hypertonic environment between the cells –> this draws water from the Apical side into the hypertonic environment between the cells –> an Osmotic pressure gradient builds –> Water moves across the Basolateral side and is absorbed by capillaries.
The colon has NO mechanisms for _____ and _____ _____ absorption, BUT is DOES have similar ion transport to the Jejunum and Ileum.
That said, it has 2 unique mechs for ion transport.
- It absorbs Na+ in the same way the DCT of the nephron does with action by ______ (which hormone?). How does this occur?
- _____ leak channels allow _____ to flow out of the cell into the lumen.
Sugar
Amino Acid
- Aldosterone
Aldosterone causes upregulation of ENaC on the Apical surface.
- K+
K+
In patients with a defect in _____/_____, a high concentration of Cl- is present in the stool, meaning there is high retention of _____ (which would otherwise be exchanged with Cl-) –> this leads to metabolic ______.
Keep in mind that chronic diarrhea results in _______, as this ion is secreted to a greater extent.
DRA/CLD
HCO3-
Metabolic Alkalosis
Hypokalemia
While villus cells of the Small and Large intestine absorb ions and water, cells in the _____ secrete Cl- (and thus water) via activation of ______ channels via neurotransmitters and hormones. Normally, villus absorption is much greater than _____ secretion.
Infection with E. coli or Cholera cause over-activation of the _____ channel via increased cAMP –> excess Cl- secreted –> Secretory diarrhea. This same mechanism occurs when the _____ is infected with Cholera bc it increases _____ in the plasma –> elevates cAMP in crypt cells –> so on…
Crypts
CFTR
Crypt
CFTR
Pancreas
VIP
How long does secretory diarrhea from Cholera typically last, and why?
It typically lasts 5-6 days. This is because Crypt cells are typically turned over every 5-6 days.
