HOW THE SMALL INTESTINE ABSORBS WATER AND SALTS ?

Only water is governed by physical laws that control the flow of fluids, but ions and organisms are not.

Electrolytes need active transfer, but water does not.

1-Intestinal Absorption.

Due to the functional physiognomy of the intestinal mucosa (selective permeability due to the conjunction of physical forces and energy-dispensing respiratory processes). Its absorption of water and salts involves two different transport mechanisms:

- The former is active, linked to cellular metabolism. They result from electrolytic dissociation, and the quality of transport system.

-The second, on the other hand, is passive, governed solely by the laws of hydraulics and osmosis of which water is naturally the subject.

2-Experiments And Observations.

To prove that some substances like water and mineral salt do not require the osmotic law, experiments are carried out on intestinal loops in place or in vitro and the use of radioactive atoms :

1-With deuterium oxide and radioactive sodium, we see that for water, as for the sodium ion, exchanges take place in both directions, from the intestine to the blood and vice versa, one prevailing over the other depending on the case: water resorption is faster with hypotonic or isotonic solutions and the absorption of salts occurs more easily near isotonicity.

2-A hypertonic solution of sodium chloride, introduced into the intestine, absorbs only sodium and chloride ions. While water is neglected.

3-The solutions of mineral salts are absorbed into different speeds depending on the nature of the dissolved bodies. Cations enter the blood quickly and successively potassium, sodium, lithium, others slowly like calcium and magnesium. The anions are classified in the order: chlorine, bromine, iodine, nitrate, sulphide trioxide. Citrate ions pass only slowly and incompletely, oxalates and fluorides not at all.

4-Most of the calcium salts are transformed in the stomach into chloride and acid phosphate. Their absorption or not depends on the acidity or alkalinity of the pH, that is to say, depending on the environment of the intestinal chyme. If these are soluble and therefore dissociated; their residence is naturally in…