During micturition, the urinary bladder________and the urethral sphincter __________.

Answer

To answer the question, "During micturition, the urinary bladder________and the urethral sphincter __________," we can break it down step by step:

### Step 1: Understanding Micturition
Micturition is the process of expelling urine from the urinary bladder. It involves a series of coordinated actions between the bladder and the urethral sphincter.

### Step 2: Role of the Urinary Bladder
The urinary bladder is a muscular sac that stores urine. When the bladder fills with urine, its walls stretch. This stretching triggers receptors in the bladder wall, which send signals to the nervous system indicating that the bladder is full.

### Step 3: Contraction of the Urinary Bladder
During micturition, the smooth muscles lining the bladder contract. This contraction helps to push the urine out of the bladder and into the urethra.

### Step 4: Role of the Urethral Sphincter
The urethral sphincter is a muscle that surrounds the urethra. It controls the release of urine from the bladder. For urine to be expelled, the urethral sphincter must relax.

### Step 5: Conclusion
Putting it all together, during micturition:
- The urinary bladder **contracts** to expel urine.
- The urethral sphincter **relaxes** to allow urine to flow out.

### Final Answer:
During micturition, the urinary bladder **contracts** and the urethral sphincter **relaxes**.

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