Summary
Kidneys, ureters, bladder and urethra remove metabolic waste and balance water.
In depth
Kidneys filter around 180 litres of blood per day to produce 1 to 2 litres of urine. The bladder stores urine. Other excretory organs: lungs (CO2), skin (sweat) and liver (bile pigments).
Kidneys also regulate blood pressure, pH and red cell production via erythropoietin. Urine composition reflects needs.
Example: kidney stones form from crystallised minerals.
The urinary system consists of two kidneys, ureters, a bladder and urethra. Kidneys contain about a million nephrons each and receive about 20 to 25 percent of cardiac output. Besides excretion they regulate blood volume, pressure, pH, electrolytes, produce erythropoietin and renin, and activate vitamin D. Urine contains water, urea, salts and creatinine, with a pale yellow colour from urochrome.
Problems include kidney stones, infections, and chronic kidney disease (often from diabetes and hypertension), treated by dialysis or transplant. Other excretory organs are the lungs (CO2), skin (sweat) and liver (bile pigments). Urine tests detect glucose, protein, ketones and pregnancy hormones.
Example: a healthy adult produces about 1 to 2 litres of urine a day, depending on fluid intake.
Frequently asked questions
What is Excretory System?
Kidneys, ureters, bladder and urethra remove metabolic waste and balance water.
Which area of biology covers Excretory System, and how advanced is it?
Excretory System is one of the 51 topics in Human Physiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Circulatory System, Blood Components, Nephron Function.
Can you give an example of Excretory System?
Dialysis replaces kidney function.
What should I learn before Excretory System?
Excretory System is a Beginner topic, so no earlier topic is required. Other Beginner topics in Human Physiology that pair well with it include Homeostasis, Tissues and Organs, Skeletal System.
What topics are related to Excretory System?
The closest topics to Excretory System are Circulatory System, Blood Components, Nephron Function, Digestive System. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Excretory System?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Excretory System. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Excretory System different from Circulatory System?
Excretory System: Kidneys, ureters, bladder and urethra remove metabolic waste and balance water. Circulatory System: The heart, blood vessels and blood that transport materials around the body. Read both side by side and note what each one explains.
How should I study Excretory System step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Circulatory System and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.