Why does pee come out in a stream?

Pee comes out in a stream due to the coordinated contraction of the bladder muscles, specifically the detrusor muscle, which pushes urine through the urethra. The urethra acts as a conduit, and the flow is directed by the relaxation of the sphincter muscles. This combination of muscle contractions and the urethra's structure facilitates a steady stream of urine during urination.