Urinary Bladder – Tutorial
Please read Unit 11 – Introduction to Urinary System Tissues prior to completing the activities in this chapter.
Introduction to the Urinary Bladder
The urinary bladder is an expandable muscular organ in the hypogastric region of the lower abdominopelvic cavity that receives urine from the ureters and temporarily stores it until urination. The wall of the urinary bladder is able to greatly stretch as it fills with urine, so the size and shape of the urinary bladder varies greatly depending on the volume of urine it contains. When the bladder is empty, its mucosa exhibits distinct folds known as rugae that stretch and flatten allowing the lumen of the bladder to expand as it fills with urine.
The lumen of the bladder is lined with transitional epithelium. Transitional refers to the fact that the shape of superficial cells near the apical surface changes or transitions from large, plump, cuboidal-like cells when the lumen is empty to squamous-like when the lumen fills with urine and the walls distend (stretch) causing the superficial cells to flatten. Transitional epithelium is well adapted to lining the urinary tract as it can tolerate repeated cycles of stretching and recoiling (filling and emptying with urine) without damage. The superficial cells near the apical surface of transitional epithelium also protect deeper layers of the bladder wall from the harmful effects concentrated (hyperosmotic) urine.
The muscularis layer of the urinary bladder wall contains a middle circular layer of smooth muscle sandwiched between inner and outer longitudinal layers of smooth muscle. Collectively, these three layers of smooth muscle form the detrusor muscle of the bladder wall which contracts to help push urine out of the bladder and into the urethra during urination.
Tutorial: Use the image slider below to learn more about the structure and characteristics of the urinary bladder.
Microscopy: Use the image slider below to learn how to use a microscope to study the urinary bladder on a microscope slide.
Tutorial: Use the hotspot image below to learn more about the structure and function of the urinary bladder.
Tutorial: Use the hotspot image below to learn more about the characteristics of transitional epithelium lining the urinary bladder.
