What is the distal convoluted tubule associated with?

What is the distal convoluted tubule associated with?

• A. Promotes sodium reabsorption; water will follow; concentrates urine.
• B. Primary site of filtration.
• C. Reabsorbs most of the water.
• D. Is impermeable to solutes.

Answer: (A)

The distal convoluted tubule mainly handles fine-tuning of salt balance by reabsorbing sodium under hormonal control. Aldosterone increases the activity of sodium transport mechanisms in this region, so more sodium is reabsorbed back into the blood. As sodium leaves the filtrate, water tends to follow by osmosis, which reduces sodium loss in urine and helps regulate blood volume and pressure. The final concentration of urine is mainly determined later in the collecting duct where water permeability is controlled by ADH, but the DCT’s sodium reabsorption with water following is the key idea behind this option. In contrast, filtration occurs in the glomerulus, most water reabsorption happens earlier in the nephron (especially the proximal tubule), and the distal tubule does transport and reabsorb solutes rather than being impermeable to them.

The distal convoluted tubule mainly handles fine-tuning of salt balance by reabsorbing sodium under hormonal control. Aldosterone increases the activity of sodium transport mechanisms in this region, so more sodium is reabsorbed back into the blood. As sodium leaves the filtrate, water tends to follow by osmosis, which reduces sodium loss in urine and helps regulate blood volume and pressure. The final concentration of urine is mainly determined later in the collecting duct where water permeability is controlled by ADH, but the DCT’s sodium reabsorption with water following is the key idea behind this option. In contrast, filtration occurs in the glomerulus, most water reabsorption happens earlier in the nephron (especially the proximal tubule), and the distal tubule does transport and reabsorb solutes rather than being impermeable to them.