Final answer:
The base of the bladder is structurally pushed upward and forward during engagement such as in late pregnancy, affecting its capacity and possibly leading to more frequent urination.
Step-by-step explanation:
Structurally, the base of the bladder is pushed upward and forward when engagement occurs especially during late pregnancy. The trigone, a triangular area at the bladder base, maintains its location as the urethra begins inferiorly and centrally to the two ureteral openings. In females, the bladder lies anterior to the uterus and is compressed by the enlarging uterus during late pregnancy, which can lead to increased frequency of urination due to reduced bladder capacity. In males, the bladder is positioned above the prostate and is not affected in this way.
The urinary bladder is a highly distensible, retroperitoneal organ lined by transitional epithelium, which allows for substantial volume changes. Regular urinary bladder volumes in adults can range from nearly zero to 500-600 mL, but the bladder’s ability to distend superiorly and hold this volume of urine is impacted during engagement due to the compression exerted by the uterus.