part_of starts_at ends_at bladder trigone EMAPA:35174 anatomical_structure The bladder trigone (syn: dorsal bladder neck) (TS:22-TS:28) is the triangular-shaped dorsal region of the bladder neck located between the ureters and the opening of the pelvic urethra. The ureter orifices form the base of the trigone and the urethra opening, the apex. The urothelium of bladder trigone has a smooth surface (as opposed to folded luminal surface of the urothelium of the bladder fundus). The morphology of the trigone changes from isosceles to equilateral triangle during development, as the distance between the ureters and pelvic urethra lengthens. Lineage analysis has shown that the urothelium derives from the urogenital sinus and the muscle derives from differentiates from the intersecting detrusor muscle and longitudinal urethral muscle fibres. Comprised of urothelium, lamina propria and detrusor muscle of bladder trigone, intercalated with ureteral smooth muscle of trigone. Also contains ureter junction of bladder trigone and urethra junction of bladder trigone. dorsal bladder neck bladder neck TS22 TS28