All are true about urinary bladder except -

Ans. is 'b' i.e., Trigone mucosa is thrown into rugaeInterior of bladder and wall of bladdero Linining epithelium of bladder mucosa is transitional epithelium. When empty mucosa is thrown into rugae except in trigone, where mucosa is smooth and firmly adherent.o Ureters open at the lateral angles of the trigone and internal urethral orifice lies at the apex. Interureteric ridge (Mercier's bar) forms the base of trigone (line joining two ureteric orifices). Distance between ureteric orifices is 2.5 cm when empty and 5 cm when bladder is distended.o In males, there is a bulging immediately posterior to the urethral orifice produced by median lobe of prostate, is called the vulva vesicae.o Just beneath the mucosa of trigone there is layer of smooth muscle, Trigonal muscle of Bell which replaces the submucous coat in trigone area.Coronal section through the bladder and prostate to show the interior of the bladder.o Deep to the mucosa, there is submucosa (submucosal coat) except in the region of trigone, where submucosal coat is replaced by, smooth muscle layer (trigonal muscle of Bell).o Deep to submucosal coat, there is muscular coat, called detrusor muscle. In the region of trigone, muscular coat (detrusor muscle) is separated from trigonal muscle of Bell by fascia of waldeyer.