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Histology of the bladder
Make it clearer
If you cut the wall of the bladder and look at it under the microscope, you do not see a uniform material, you see layers stacked one on top of another. From the inside out there are four: the lining epithelium, the inner surface in contact with urine; the lamina propria, the supporting tissue underneath; the muscularis propria, which is the detrusor muscle of the wall; and on the outside the serosa or the adventitia, the outer covering.
The layer that touches the urine has its own name: urothelium, a stratified epithelium, meaning several rows of cells, and a highly specialized one. Its trick is that its thickness is not fixed. With the bladder relaxed it looks thick, with many rows stacked up, and when the bladder fills and stretches, those same rows rearrange into fewer layers without tearing. It is what a knit sweater does when you stretch it: the fabric flattens and opens up, but it does not rip. Because of that ability to transition, it is also called transitional epithelium.
In brief
From the inside out, the bladder wall is organized into a lining epithelium, lamina propria, muscularis propria, and serosa or adventitia.
The lining is a specialized stratified epithelium, the urothelium, with three histologic layers; the lamina propria separates it from the muscularis propria, which is the detrusor muscle.
When the bladder is relaxed the urothelium is thick, and it reorganizes into fewer layers when the bladder is distended, without being damaged; that is why it is also called transitional epithelium.
Sources (2)
- National Center for Biotechnology InformationHistology, Bladder. StatPearls
- OpenStax, Rice UniversityAnatomy and Physiology 2e, 25.2 Gross Anatomy of Urine TransportPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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