A 65-year-old male with benign prostatic hyperplasia (BPH) is prescribed an alpha-1 adrenergic receptor antagonist. This drug primarily improves urinary flow by causing relaxation of which structure?

✓ Correct Answer: Option B

Alpha-1 adrenergic receptors are abundant in the smooth muscle of the prostate gland and bladder neck (including the internal urethral sphincter). Blocking these receptors causes relaxation, reducing outflow obstruction and improving urinary flow in BPH.