Transitional epitheliumThe lining of the bladder, also called urothelium. Its cells change shape as the bladder fills.
Lamina propriaConnective tissue under the epithelium. It fills the core of each fold.
Detrusor muscleThe smooth muscle coat of the bladder. When it contracts, urine is pushed out.
Inner longitudinal layerThe innermost muscle layer. Its fibers run lengthwise, so they are drawn cut across.
Middle circular layerThe middle muscle layer. Its fibers run around the bladder.
Outer longitudinal layerThe outermost muscle layer. Its fibers run lengthwise again.
AdventitiaThe outer coat of connective tissue. Over the top of the bladder a serosa of peritoneum covers the wall instead.
Ruga (fold)A fold of the lining of an empty bladder. The folds flatten out as the bladder fills.
LumenThe space inside the bladder. The lining faces it.
The lining 4
Umbrella cellsLarge surface cells that face the lumen. They are dome-shaped in an empty bladder and flat in a full one.
Intermediate cellsThe cell layers between the umbrella cells and the basal cells.
Basal cellsSmall cells of the deepest layer. Each one rests on the basement membrane.
Basement membraneA thin sheet under the basal cells. It separates the epithelium from the lamina propria.
How this list was compiled: Every name read on 2026-10-03 and kept only where two independent sources give it. (1) Henry Gray, Anatomy of the Human Body (1918, public domain), The Urinary Bladder, structure, https://www.theodora.com/anatomy/the_urinary_bladder.html : the folds of the empty bladder, the transitional epithelium and the muscular coat in three layers, outer longitudinal, middle circular and inner longitudinal. (2) Wikipedia, text only: Bladder, Transitional epithelium and Detrusor muscle, https://en.wikipedia.org/wiki/Bladder and https://en.wikipedia.org/wiki/Transitional_epithelium . (3) U.S. National Cancer Institute, SEER Training Modules, Urinary Bladder, https://training.seer.cancer.gov/anatomy/urinary/components/bladder.html : transitional epithelium, rugae, the detrusor muscle and the outer coat. (4) Winder and others, Signalling molecules in the urothelium, BioMed Research International (2014), open access, https://europepmc.org/article/PMC/PMC4142380 : umbrella, intermediate and basal cells, the basal lamina and the lamina propria. (5) A color atlas of histology (2006), read by full-text search on archive.org, https://archive.org/details/coloratlasofhist0004gart : an adventitia or serosa around the bladder, and dome-shaped surface cells in the empty bladder that flatten when it is distended. The drawing is our own. Licence: own work
The drawing: Drawn for this site on 2026-10-03 from plain geometry. Own original drawing; nothing traced or copied. Not to scale. Licence: own work
How it works
This is a drawing of a bladder slide, not a photo. The first view cuts through the wall of an empty bladder, with the lumen at the top. The second enlarges the lining, empty above and stretched below.
Read the full guide
The wall
Read down from the lumen. The folded lining is transitional epithelium on a core of lamina propria, and one fold is a ruga. Under it lie the three layers of the detrusor muscle: inner longitudinal, middle circular and outer longitudinal. The adventitia is the outer coat.
The lining
The upper block is the lining of an empty bladder: dome-shaped umbrella cells on top, intermediate cells under them and small basal cells on the basement membrane. The lower block shows the same layers stretched thin in a full bladder.
Dome-shaped surface cells mean the bladder was empty when the slide was made.
Questions and answers
What are the layers of the bladder wall?
From the lumen outward: transitional epithelium, lamina propria, the detrusor muscle with its inner longitudinal, middle circular and outer longitudinal layers, and an outer adventitia. Over the top of the bladder a serosa of peritoneum covers the wall instead.
What type of epithelium lines the urinary bladder?
Transitional epithelium, also called urothelium. It is several cells thick, and its surface cells change from dome-shaped to flat as the bladder fills, which lets the lining stretch.
What are umbrella cells?
The large cells on the surface of transitional epithelium, facing the lumen. They are dome-shaped in an empty bladder and flattened in a full one. Intermediate cells and basal cells lie under them.
How does an empty bladder differ from a full one on a slide?
In an empty bladder the lining is thrown into folds called rugae and the surface cells are dome-shaped. In a full bladder the folds are flattened out and the surface cells are stretched flat.