ANATOMY

Detailed explanation-1: -B: Approximately 180 L of filtrate enters the nephrons each day; of that volume, 65% is reabsorbed in the proximal tubule. In the proximal tubule, solute molecules move by active transport and cotransport from the lumen of the tubule into the interstitial fluid.

Detailed explanation-2: -Reabsorption of water and specific solutes occurs to varying degrees over the entire length of the renal tubule. Bulk reabsorption, which is not under hormonal control, occurs largely in the proximal tubule. Over 70% the filtrate is reabsorbed here.

Detailed explanation-3: -RE-ABSORPTION involves several structures in and around the nephrons. Approximately 178.5 L of the 180 L of filtrate produced every day is reabsorbed (99.2% of filtrate is reabsorbed).

Detailed explanation-4: -Proximal tubules are responsible for reabsorbing approximately 65% of filtered load and most, if not all, of filtered amino acids, glucose, solutes, and low molecular weight proteins. Proximal tubules also play a key role in regulating acid-base balance by reabsorbing approximately 80% of filtered bicarbonate.

Detailed explanation-5: -The brush border and the extensive length of the proximal tubule dramatically increase the surface area available for reabsorption of substances into the blood enabling around 80% of the glomerular filtrate to be reabsorbed in this segment.