part_of starts_at ends_at urinary system urogenital sinus bladder anatomical_structure The bladder (BL) (TS:22-TS:28) is comprised of urothelium of bladder (subdivided into layers and cell types), lamina propria of bladder (subdivided into layers), detrusor muscle of bladder and surrounded by an outer layer of bladder (subdivided into serosa of bladder or adventitia of bladder). Also includes vasculature of bladder and nerve of bladder. Derived from primitive bladder (TS:19-21). Bladder is also subdivided into regions; bladder fundus and bladder neck (subdivided into bladder trigone and ventral bladder neck). Part of the urogenital sinus and part of the urinary system. EMAPA:18321 lower urinary tract TS22 TS28