when sodium ions are reabsorbed through the wall

Sodium ions are reabsorbed throughout the nephron, the functional unit of the kidney, but the process is most active in the:

Proximal Convoluted Tubule (PCT): This is the first part of the nephron where a large portion of the filtered fluid, including sodium ions, is reabsorbed back into the bloodstream. Here, reabsorption happens through a combination of:

Active transport: Sodium-Potassium ATPase pumps actively transport sodium ions from the lumen (inner space) of the tubule into the blood across the basolateral membrane.

Passive transport: Other solutes like glucose and amino acids are co-transported with sodium, following its movement created by the pumps.