Fluid & Electrolyte Q 107

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Disease of which of the following structures is most likely to affect electrolyte reabsorption?

  

    A. Glomerulus

    B. Renal tubules

    C. Bladder

    D. Renal pelvis

    

    

Correct Answer: B. Renal tubules

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The renal tubules are the site of electrolyte reabsorption. From the PCT, the non-reabsorbed filtrates move on to the nephron loop. The nephron loop functionally divides into a descending and an ascending limb. In the ascending limb, Na moves passively down its concentration gradient in the thin segment of the ascending limb, and also sodium, potassium, and chlorides get reabsorbed together through a symporter in the thick segment of the ascending limb.

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Option A: The glomerulus is the site of electrolyte filtration. Glomerular filtration is the initial process in urine production. It is a passive process in which hydrostatic pressure pushes fluid and solutes through a membrane with no energy requirement.

Option C: The bladder is where the urine is stored. The bladder is essentially a muscular sac with three layers. Its three layers are similar to the ureter except that the muscular layer has muscle fibers organized in inner and outer longitudinal layers and a middle circular layer.

Option D: The renal pelvis is where urine travels as it moves from the collecting ducts to the ureter. Once the production of urine is complete, it travels through a structure called ureter for urine storage in the bladder. There are two ureters in a human body; one on each side; left and right.

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