What is the bladder?

The bladder is a hollow and muscular organ that collects and stores pee (urine). The bladder wall is made of the following 4 layers:

  • An inner lining made up of cells called urothelial or transitional cells. This is called the urothelium. It stops pee being absorbed back into the body.
  • A layer of connective tissue.
  • A layer of muscle, called the detrusor muscle.
  • An outer layer of fatty tissue.
The bladder
Image: The bladder
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Where is the bladder in the body?

The bladder is in the lower part of the tummy (abdomen), called the pelvis. This is the area between the hips. It is supported by a group of muscles called the pelvic floor muscles. These sit at the bottom of the pelvis.

The bladder in the body
Image: The bladder in the body


What does the bladder do?

The bladder collects and stores pee (urine). It can usually hold about 300 to 400mls of pee. Pee is made of water and waste products. It is made in the kidneys and moves from the kidneys to the bladder through long tubes called ureters.

As your bladder fills with pee it expands to store it. When it is full, it sends messages to the brain. These are called nerve signals. They make you feel like you need to pee (pass urine).

When you need to pee, the urine exits your bladder through a tube called the urethra. The urethra opens in front of the vagina, or at the tip of the penis.

The bladder and urethra are supported by the pelvic floor muscles. The muscle that wraps around the urethra is called the urethral sphincter. It works like a valve to keep the opening at the bottom of the bladder closed until you want to pee.

To empty your bladder, the pelvic floor muscles relax to open your urethral sphincter. At the same time, the bladder muscles tighten to push the pee out.

The lymphatic system and bladder cancer

The lymphatic system helps protect us from infection and disease. It is part of the body’s immune system. It is made up of fine tubes called lymphatic vessels. These vessels connect to groups of small lymph nodes throughout the body.

The lymphatic system drains lymph fluid from the tissues of the body before returning it to the blood. Lymph nodes are sometimes called lymph glands. They filter bacteria (germs) and disease from the lymph fluid. When you have an infection, some lymph nodes may swell as they fight the infection.

Sometimes, cancer can spread through the lymphatic system. If bladder cancer spreads in this way, it is most likely to affect the lymph nodes near the bladder. These are called pelvic lymph nodes.

Pelvic lymph nodes

Image: Pelvic lymph nodes

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr Ursula McGovern, Consultant Medical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 November 2022
Next review: 01 November 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

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