Urinary System Structures and Functions

Urinary System Structures and Functions

Urinary System Structures and FunctionsThe urinary system include the two kidneys, two ureters, the urinary bladder (or simply, bladder), two sphincter muscles, and the urethra. Illustration of the urinary tractThese structures, including the nerves that control them, work in different ways. But generally, the urinary system works to form urine, store it, and carry it outside the body.

The different structures of the urinary system and their functions:

The Kidneys

The kidneys are two bean-shaped organs located near the middle of the back just below the rib cage. Each kidney is about the size of your fist.

The kidneys help to remove urea from the body. Urea is a waste product that forms when foods that contain protein are broken down in the body. Proteins are found in meat, poultry, and some vegetables. Urea, along with other waste products formed by cells is transported through the bloodstream to the kidneys.

Within the kidneys are tiny filtering structures called nephrons. The nephrons help eliminate urea, other waste products, and excess water from the body. The combination of waste products and excess water constitutes urine.


Once urine is formed in the kidneys, it flows into two thin, tube-like organs called ureters. Each ureter connects each kidney to the bladder.

urinary system


The bladder, also called urinary bladder, is a hollow muscular organ that sits in the pelvis and held in place by structures attached to other organs and the pelvic bone.

The bladder receives the urine coming from the kidneys that passes through the ureters. It normally helps to store urine until you empty it during urination.

If you do not have problems with your urinary system, your bladder can hold up to 16 ounces, or 2 cups, of urine comfortably for up to 5 hours.


To prevent leaking of urine, sphincter muscles in the opening of the bladder normally contract.


Urine flows to the urethra when sphincter muscles surrounding the tube just below the bladder relax. Urine exits the body through the opening of the urethra, called external urethral orifice.


Nerves play a vital role in “telling” the bladder when it is time to empty it, or urinate.

Normally, you may notice a feeling that you need to urinate as the bladder is filled with urine. This sensation grows stronger as the bladder continues to be filled. When it reaches its limit, nerves from the bladder inform the brain that the bladder is full. During this time, your urge to empty your bladder intensifies.


Urination occurs when the brain signals the muscles in the bladder to tighten. As a result, urine is squeezed out of the bladder. The brain also signals the sphincter muscles to relax allowing urine to pass and flow through the urethra.