The Excretory System

Excretion = The process by which wastes and excess substances are removed from an organism Organs of excretion are: Lungs Kidneys Liver Skin

Liver Liver – removes harmful substances from the blood such as bacteria, certain drugs, and hormones The liver breaks down excess amino acids to form urea Too much alcohol can lead to cirrhosis of the liver Bile is considered an excretory product of the liver

A healthy liver and the liver of a person with cirrhosis

Kidneys – filter urea from the blood to make urine The Urinary System The urinary system is included in the excretory system. Kidneys – filter urea from the blood to make urine Ureter – tube through which urine passes from each kidney to the urinary bladder Urinary Bladder – where urine is stored Urethra – the tube that carries urine from the bladder to the outside of the body

Kidneys Organs of the excretory system that act like filters. The two kidneys are located near the spine in the middle of the back. They are protected by lower ribs and covered by layers of fat. Without the kidneys, it would not take long before the body’s system would be poisoned. It is possible to function with only one kidney.

Urine Waste drains out of the kidneys in the form of urine. Urine is about 95% water and 5% urea (protein from protein breakdown). Fresh urine has no bacteria in it.

Lungs An organ of the excretory system that rids the body of carbon dioxide and water (water vapor).

Skin An organ in the excretory system which removes excess heat. When the body becomes too warm, extra heat is lost Evaporation of sweat removes heat and cools the body

The skin is the largest organ in the body It contains sweat glands through which sweat is released Sweat is made up of: 98% water 2% salt Small amounts of urea

Excretory Disorders Kidney stones - result when urine becomes too concentrated and substances in the urine crystallize to form stones Risk factors: -Family or personal history -Being an adult (40+) -Being a man -Dehydration -Diets high in protein, sodium, and sugar -Obesity -Digestive diseases and surgery -Other medical conditions

Excretory Disorders Renal Failure – results when the kidneys fail to function correctly which leads to abnormal levels of fluids in the body Kidney dialysis averages 4 hours per session, 3 times per week.

Ways to Protect Your Kidneys Eat a diet low in fat and salt Exercise most days of the week Drink water (~8 glasses/day) Avoid tobacco Limit alcohol