Anatomy and physiology of the urinary system

Before treating bladder problems, it is useful for you to know the basic anatomy and physiology of the urinary system as it will make it easier for you to understand the treatment. The urinary system consists of organs whose main function is the formation and periodic excretion of urine.

The urinary system ensures the excretion of waste substances from the body through the fluid formed by the kidneys. The process of constant urine flow in the upper urinary tract and occasional excretion from the lower urinary tract also plays an important role in cleaning the entire system from microbes.

The urinary system consists of:

  • upper urinary tract — includes everything above the bladder level: kidneys and urethras (urinary tubes) that take the urine from the kidneys to the bladder;

  • lower urinary tract — everything from the urinary bladder to the top of the urethra (urinary tube).

The kidneys filter about 180 litres of blood throughout the day, of which one litre is excreted as urine. After the kidneys, urine is taken to the bladder through two urinary tracts (pipe-like organs). Ureters are 25-30 cm long and pass through the bladder wall, and the mucous membrane of the bladder next to the opening prevents the return of urine to the kidneys.

This is very important because if the urine returns to the kidneys, it can cause difficulties such as infections and kidney damage.


The bladder is a hollow and stretchable organ that relaxes when empty, and tightens when it is full. It consists of the detrusor (a smooth muscle) and collagen.


The bladder typically stores 400-500 ml of urine, but it can store more (up to 750 ml) when a person has a strong need to urinate.

Urethra and sphincters

Two sphincters, internal and external, control the excretion of urine from the bladder through the urethra. The internal sphincter prevents the leakage of urine until the pressure in the bladder increases to a certain level. In healthy people, the external sphincter is wilfully controlled. In men, the mechanism of the external sphincter is more complex than in women.

The urethra is the end of the urinary system, i.e. an ‘output’ channel of the bladder whose function is to excrete urine outside of the body. In men, it is on average 22.3 cm long, it passes partly through the prostate, and ends at the end of the penis, with an opening on the glans.

In women, the urethra is significantly shorter. It is only 3-5 cm long, extending from the bladder to the outer opening under the clitoris.


The urinary system consists of a complex network of nerves and organs working together with the brain and the spinal cord. Under normal conditions, the brain and the bladder “communicate” to successfully store and excrete urine.

In case this communication is disabled for some reason, e.g. in the case of a spinal cord injury, this will lead to difficulties.




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