MICROANATOMY

Detailed explanation-1: -Definition. The internal urethral orifice is placed at the apex of the trigonum vesicæ, in the most dependent part of the bladder, and is usually somewhat crescentic in form; the mucous membrane immediately behind it presents a slight elevation, the uvula vesicæ, caused by the middle lobe of the prostate.

Detailed explanation-2: -The fundus is the base of the bladder, which is formed by the posterior wall and contains the trigone of the bladder, and is lymphatically drained by the external iliac lymph nodes.

Detailed explanation-3: -The internal urethral sphincter regulates involuntary control of urine flow from the bladder to the urethra, and the external urethral sphincter provides voluntary control of urine flow from the bladder to the urethra.