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The bladder

The bladder is a hollow, muscular sac that stores urine (wee or pee). It is located in the pelvis and is part of the urinary system.

The urinary system also includes two kidneys, two tubes called ureters that lead from the kidneys into the bladder, and another tube called the urethra that leads out of the bladder. In males, the urethra is a long tube that passes through the prostate and down the penis. In females, the urethra is shorter and opens in front of the vagina (birth canal).

The kidneys produce urine, which travels to the bladder through the ureters. The bladder is like a balloon and expands as it fills with urine. When you are ready to empty your bladder, the bladder muscle contracts, and urine passes through the urethra and out of the body.

Layers of the bladder wall

There are four main layers of tissue in the bladder.

urotheliumThe inner layer. It is lined with cells called urothelial cells that stop urine being absorbed into the body.
lamina propriaA layer of tissue and blood vessels surrounding the urothelium.
muscularis propriaThe thickest layer. It consists of muscle that contracts to empty the bladder.
perivesical tissueThe outer layer. Mostly made up of fatty tissue, it separates the bladder from nearby organs.

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This information is reviewed by

This information was last reviewed in February 2022 by the following expert content reviewers: Prof Dickon Hayne, Professor of Urology, UWA Medical School, The University of Western Australia, Chair of the Bladder, Urothelial and Penile Cancer Subcommittee, ANZUP Cancer Trials Group, and Head of Urology, South Metropolitan Health Service, WA; A/Prof Tom Shakespeare, Director, Radiation Oncology, Coffs Harbour, Port Macquarie and Lismore Public Hospitals, NSW; Helen Anderson, Genitourinary Cancer Nurse Navigator (CNS), Gold Coast University Hospital, QLD; BEAT Bladder Cancer Australia; Mark Jenkin, Consumer; Dr Ganessan Kichenadasse, Lead, SA Cancer Clinical Network, Commission of Excellence and Innovation in Health, and Medical Oncologist, Flinders Centre for Innovation in Cancer, SA; A/Prof James Lynam, Medical Oncology Staff Specialist, Calvary Mater Newcastle, NSW; Jack McDonald, Consumer; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Tara Redemski, Senior Physiotherapist – Cancer and Blood Disorders, Gold Coast University Hospital, QLD; Prof Shomik Sengupta, Consultant Urologist, Eastern Health and Professor of Surgery, Eastern Health Clinical School, Monash University, VIC.