Problem 6 - Biology: The Dynamic Science

Question

Which of the following correctly describes a part of kidney function? a. Collecting ducts dilute urine because they are permeable to salt but not water. b. In the ascending loop of Henle, \(\mathrm{Na}^{+}\) and \(\mathrm{Cl}^{-}\) move into the tubules because the osmolarity of the filtrate is increased. c. The descending loop of Henle receives filtrate from the ascending loop. d. The distal convoluted tubule pumps water into the tubule by active transport. The renal pelvis receives urine from the collecting ducts and carries it to the ureters.

Step-by-Step Solution

Answer

The correct answer is: The renal pelvis receives urine from the collecting ducts and carries it to the ureters.

Step 1: Understand each part of the kidney

The kidney consists of many sections, each with its unique function. The collecting ducts, ascending loop of Henle, descending loop of Henle, distal convoluted tubule and renal pelvis are all parts of the nephron in the kidney, where urine production happens. The collecting ducts reabsorb water and concentrate urine. The ascending loop of Henle is permeable to ions but not water, and the descending loop of Henle is essentially the opposite\u2013it is permeable to water but not to ions. The distal convoluted tubule helps adjust the pH of urine and reabsorbs sodium ions. The renal pelvis collects urine from the nephrons and transfers it to the ureters.

Step 2: Evaluate each choice

Choice a: Collecting ducts do not dilute urine; instead, they concentrate the urine by reabsorbing more water. So, this statement is incorrect.Choice b: The ascending limb of the loop of Henle is not permeable to water, only to some ions such as \(\mathrm{Na}^{+}\) and \(\mathrm{Cl}^{-}\). Sodium and chloride ions move out of the ascending limb into the surrounding renal tissue to create an osmotic gradient, but not because the osmolarity of the filtrate is increased. So, this statement is partly right but not completely accurate.Choice c: Actually, the ascending loop of Henle sends filtrate to the distal convoluted tubule, not the descending loop of Henle. This statement is incorrect.Choice d: The distal convoluted tubule does not pump water into the tubule; instead, it adjusts the concentration of ions and pH of the urine. So, this statement is incorrect.Choice e: The last statement is correct. The renal pelvis does indeed receive urine from the collecting ducts and sends it to the ureters, which then transport the urine to the bladder for storage and eventual expulsion from the body.

Step 3: Choose the correct answer

After evaluating each choice, the only completely accurate statement is Choice e: 'The renal pelvis receives urine from the collecting ducts and carries it to the ureters.'