reabsorption of sodium and chloride ions occurs in the proximal tubule.
where does reabsorption of sodium and chloride ions occur?
the proximal tubule
normally, chloride reabsorption begins in the proximal tubule and nearly 60% of chloride is filtered here. in a person with hyperchloremia, the absorption of chloride into the interstitial fluid and subsequently into the blood capillaries is increased. this means the concentration of chloride in the filtrate is decreased, therefore, a decreased amount of chloride is being excreted as waste in the urine. in the proximal tubule chloride reabsorption occurs in two parts. in the 1st phase, organic solutes (such as phosphates, amino acids, glucose and anions), sodium ions, and hydronium ions are reabsorbed from the filtrate fluid into the interstitial fluid. this is an important step because this creates the concentration gradient in which chloride concentration in the lumen will increased in comparison to the chloride concentration in the interstitial fluid. in phase 2, chloride will diffuse along the concentration gradient, which means chloride ions will travel from areas of high concentration to areas of low concentration.
hyperchloremia
ions cross the cell membrane under two influences: diffusion and electric fields. a simple example wherein two solutions—a and b—are separated by a porous barrier illustrates that diffusion will ensure that they will eventually mix into equal solutions. this mixing occurs because of the difference in their concentrations. the region with high concentration will diffuse out toward the region with low concentration. to extend the example, let solution a have 30 sodium ions and 30 chloride ions. also, let solution b have only 20 sodium ions and 20 chloride ions. assuming the barrier allows both types of ions to travel through it, then a steady state will be reached whereby both solutions have 25 sodium ions and 25 chloride ions. if, however, the porous barrier is selective to which ions are let through, then diffusion alone will not determine the resulting solution. returning to the previous example, let's now construct a barrier that is permeable only to sodium ions. now, only sodium is allowed to diffuse cross the barrier from its higher concentration in solution a to the lower concentration in solution b. this will result in a greater accumulation of sodium ions than chloride ions in solution b and a lesser number of sodium ions than chloride ions in solution a.
membrane potential