Intestine knowledge
Intestines
Food and liquid that has been ingested through the mouth passes through the small and large intestine organs of the gastrointestinal tract, which extract the solids that has been broken up by the stomach. Water absorption is primarily facilitated by the large intestine. What is secreted or not absorbed moves towards the anus.
Pictures
Fig. 1. The small intestine, surrounded by the large intestine
| Abbreviation | Name |
|---|---|
| C | Colon |
| DC | Descending Colon |
| Duod | Duodenum |
| Jej | Jejunum |
| PC | Proximal Colon |
| SI | Small Intestine |
Solute transport
The following list contains the known membrane transporters along the small and large intestines.
| Abbrev | Channel name | Location | Membrane | Direction |
|---|---|---|---|---|
| AE2 | Anion Exchanger 2 | throughout | B | Cl- in/HCO3- out |
| bAE3 | Anion Exchanger 3 (brain subtype) | ileum/colon | B | Cl- in/HCO3- out |
| Ca-ATPase | Calcium ATPase | Duod/early Jej | B | Ca out |
| CaT1 | epithelial calcium channel (ECaC) | Duod/early Jej | A | Ca in |
| CFTR | Cyastic Fibrosis Transmembrane Regulator | throughout | A | Cl- out |
| ClC2 | Chloride channel (isoform 2) | throughout | B | ? |
| ClC4 | Chloride channel (isoform 4) | throughout | A | Cl- out |
| DRA | downregulated in adenoma | Duod/ileum/C | A | Cl- in/HCO3- out |
| ENaC | Epithelial sodium channel | DC | A | Na+ in |
| GLUT2 | Glucose transporter (isoform 2) | SI | B | glu fru out |
| GLUT5 | Glucose transporter (isoform 5) | SI | A | fru in |
| H-K-ATPase | Hydrogen/potassium ATPase | DC | A | K+ in/H+ out |
| K | Unknown potassium channel(s) | throughout | B | K+ out |
| NBC | Sodium bicarbonate cotransporter | Duod/PC | B | NaHCO3- out |
| NHE (Cl- dep) | Sodium hydrogen exchanger (chloride-dependent) | DC | A | Na+ in/H + out |
| NHE1 | Sodium hydrogen exchanger (isoform 1) | throughout | B | Na+ in/H+ out |
| NHE2 | Sodium hydrogen exchanger (isoform 2) | SI/DC | A | Na+ in/H+ out |
| NHE3 | Sodium hydrogen exchanger (isoform 3) | SI/DC | A | Na+ in/H+ out |
| NKA | Sodium/potassium ATPase | throughout | B | 3 Na+ out/2 K+ in |
| NKCC1 | Sodium/potassium/chloride cotransporter (isoform 1) | throughout | B | Na+ out/K+ out/Cl- out |
| NaPi-IIb | Sodium-dependent phosphate cotransporter (Npt2b) | SI | A | 3 Na+/PO43- in |
| PAT1 | Putative anion transporter (isoform 1) | Duod/ileum/C | A | Cl- in/HCO3- out |
| SGLT1 | Sodium-glucose cotransporter (isoform 1) | SI | A | 2 Na+ in/glu in |
| ? | ileum/colon | A/P | Mg2+ in | |
| ? | throughout | P | PO43- in |
Solutes: Sodium Na+, chloride Cl-, potassium K+, hydrogen H+, bicarbonate HCO3-, phosphate PO43-, magnesium Mg2+, glu Glucose, fru Fructose. Membrane: A apical (to lumen), B basolateral (to blood), P paracellular (to interstitial space). Direction: movement of solute under normal physiological conditions.
Literature
| Title | Author |
|---|---|
| Physiology of Intestinal Absorption and Secretion | Kiela and Ghishan |
| Intestinal ion transport and the pathophysiology of diarrhea | Field |
