Question

Assertion :During micturition, urine is prevented from flowing back into the ureters.
Reason: Urethral sphincters relax during micturition.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion

The act of voiding the urine is called micturition. Besides functioning as a temporary reservoir of urine, the urinary bladder also evacuates the urine by the process of micturition at suitable intervals. When enough urine has accumulated in the bladder to distend the bladder and raise its pressure sufficiently, a spontaneous nervous activity (reflex) is initiated; this causes the smooth muscles on the bladder wall to contract and the urethral sphincters, which guard the urethra, to relax. Urine consequently flows from the bladder through the urethra to the exterior. But it is prevented from flowing back into the ureters, because the terminal part of each ureter passes obliquely through the bladder wall and is consequently closed due to compression by the contracting bladder muscles.

So, the correct answer is 'Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion'.