Correct option is C
Explanation:
Let's go through the options again:
A. P cells of the collecting duct are involved in Na+ reabsorption and vasopressin-stimulated water reabsorption.
This statement is correct.
P cells in the collecting duct are primarily involved in Na+ reabsorption and water reabsorption under the influence of vasopressin (ADH), which increases the permeability of the collecting duct to water. Hence, A is correct.
B. P cells of the collecting duct are concerned with acid secretion and HCO₃⁻ transport.
This statement is incorrect.
P cells are involved in Na+ reabsorption and water reabsorption, not in acid secretion or bicarbonate (HCO₃⁻) transport. These functions are carried out by I cells (intercalated cells) in the collecting duct. Therefore, B is false.
C. I cells of the collecting duct are concerned with acid secretion and HCO₃⁻ transport.
This statement is correct.
I cells (intercalated cells) are responsible for acid secretion and bicarbonate transport in the collecting duct. These cells help regulate the body's acid-base balance by secreting H⁺ ions and reabsorbing HCO₃⁻. Hence, C is correct.
D. The total length of the nephrons, including collecting ducts, ranges from 45 to 65 mm.
This statement is correct.
The total length of the nephrons, including the collecting ducts, typically ranges from 45 to 65 mm, depending on species and the size of the kidneys. Hence, D is correct.
Conclusion:
A: P cells are involved in Na+ reabsorption and vasopressin-stimulated water reabsorption.
C: I cells are involved in acid secretion and HCO₃⁻ transport.
D: The total length of the nephrons, including collecting ducts, ranges from 45 to 65 mm.
Thus, the correct answer is Option 3: A, C and D.
