part_of starts_at ends_at outer layer of primitive bladder adventitia of primitive bladder The adventitia of primitive bladder (apbl) (TS:20-TS:21). The outermost layer of the bladder is comprised of either a serosa or an adventitia. The adventitia refers to the outer part of the primitive bladder that is not exposed to the peritoneal cavity but is a connective tissue layer that binds it to the adventitia of the adjacent organs. Most of the bladder will be covered by serosa, but early when the primitive bladder is not developed and later in some regions (i.e. closer toward the urethra) there will instead be an adventitia. As the organs develop, more of the bladder is covered by serosa and less by an adventitia. EMAPA:36095 anatomical_structure TS20 TS21