What takes place in the disal convoluted tubule?

if you think about it, the role of the loop of henle is to essentially get as high a concentration of salts in the collecting duct as possible to get concentrated urine because it's trying to get as much water water as possible reabsorbed back into the body.

now that we know this we can pretty much work from there. after the fluid has moved through the descending limb (which is water permeable meaning that it loses water through osmosis to the tissue fluid in the medulla) and the ascending limb (which is water impermeable meaning the opposite), the fluid is very high in concentration of salts because salts keep moving into the tubule after the top of the descenting limb.

therefore, by the time the fluid gets to the distal convoluted tubule, the urine is low in water potential already. sodium ions move out of the fluid and potassium ions move into the tubule. water also continues to diffuse out of the tubule and also later on in the collecting duct. depending on how hydrated the body is, more and more water is reabsorbed back into the tissue fluid in the medulla before being absorbed by the capillaries and carried away by the blood. this is all done to prevent dehydration.