Which of the following substances is typically returned to the blood during reabsorption?

The substance that is typically returned to the blood during reabsorption is plasma proteins. In the kidney, the process of reabsorption occurs primarily in the renal tubules, where essential substances are reclaimed from the filtrate and returned to the bloodstream.

Plasma proteins, particularly albumin, are generally retained in the blood and not filtered through the glomerulus under normal conditions. When considering the role of reabsorption, the kidneys ensure that any small amounts of protein that may have been lost in the filtration process are reabsorbed back into the bloodstream to maintain proper protein levels and prevent proteinuria, which can be indicative of kidney damage.

The other substances mentioned, while relevant to kidney function, do not typically undergo reabsorption in the same manner. Urea is partially reabsorbed, but it is ultimately a waste product that the body aims to excrete. Creatinine, a waste product of muscle metabolism, is typically not reabsorbed and is excreted in urine. Excess water may be reabsorbed in certain conditions, but the primary focus in the context of reabsorption is on substances that are crucial for maintaining homeostasis, like plasma proteins.