What is the process called by which urine is expelled from the bladder?

• A. Filtration
• B. Absorption
• C. Micturition
• D. Excretion

Answer: (C)

The act of expelling urine from the bladder is called micturition. It is a coordinated process that begins when the bladder becomes full and stretch receptors trigger a reflex to contract the detrusor muscle, raising bladder pressure. At the same time, the internal urethral sphincter relaxes automatically, and the external sphincter relaxes under voluntary control to allow urine to pass through the urethra. This creates controlled voiding of urine from the bladder.

In contrast, filtration is the kidney’s initial step of filtering blood to form urine, and absorption is the movement of substances from the filtrate back into the blood. Excretion refers to the general elimination of wastes from the body, which includes urine, but it does not specifically describe the act of emptying the bladder itself.