Excretory system

The excretory system is a passive biological system that removes extra, unwanted materials from the body fluids of an organism. It helps keep the body’s balance and prevents harm. This system gets rid of waste from metabolism, which is made when cells create energy.

In humans and other amniotes like mammals, birds, and reptiles, most of this waste leaves the body as urine. We also get rid of some waste when we breathe out and, for mammals, through sweating. The main organs for this are part of the urinary system.

Since all healthy organs make waste, the whole body relies on the excretory system to work right. If it stops working, it can cause serious health problems, like kidney failure. Learning about this system shows how our bodies stay balanced and healthy.

Systems

Main article: Urinary system

The urinary system helps remove waste from our bodies. The kidneys are two bean-shaped organs that filter blood. They take out wastes and extra water to make urine. They use tiny filters called nephrons to separate what the body needs from what it doesn’t. The cleaned blood leaves through the renal vein, while urine travels through tubes called ureters to the urinary bladder, which stores it until we urinate.

Main article: Respiratory system

Our lungs also help remove waste. When we breathe out, they release gases like carbon dioxide from the blood.

Main article: Gastrointestinal tract

The large intestine moves food through the body and pushes out solid waste. It also takes in any remaining water before waste leaves the body.

Main article: Biliary system

The liver helps clean the blood by breaking down harmful substances. It changes poisons like ammonia into less harmful materials, which the kidneys then remove as urine.

Main article: Integumentary system

Our skin can also help remove waste. Sweat glands release sweat, which helps control body temperature and remove small amounts of waste. Sweat is mostly water and helps keep the body cool.

Substances

Main article: Bile
Main article: Urine
Main article: Faeces
Main article: Sweat
Main article: Breath

The excretory system helps remove waste from our bodies. Bile is made in the liver and stored in the gallbladder. It helps break down fats in our food. Urine is formed in the kidneys. It removes waste and extra water from our blood and leaves the body through the bladder. Other wastes leave our bodies as faeces, sweat, and breath.

Clinical significance

Kidney stones

Main article: Kidney stone disease

Kidney stones are hard bits that can form inside the kidneys. They are made from things like calcium and uric acid. Sometimes these stones are small enough to pass out of the body with urine, but larger stones can get stuck and cause pain. Doctors can help break up big stones using special waves or tools.

Pyelonephritis

Main article: Pyelonephritis

Pyelonephritis is an infection in the kidneys that happens when bacteria get into the urinary system. This can make a person sick with fever and pain. Doctors treat it with medicines called antibiotics to kill the bacteria. Most people get better with treatment.