Excretory System

What is the excretory system? The organs that remove metabolic wastes from the body Skin Lungs Liver Kidneys

Skin The skin secretes excess salt, water and a small amount of urea Urea is a toxic compound that is produced by the breakdown of amino acids to produce energy.

Lungs The lungs rid the body of excess carbon dioxide.

Liver The liver converts excess nitrogen-containing compounds into urea. Urea is easily excreted by the kidneys.

Kidneys Kidneys remove wastes from the blood while regulating the amount of salt and water in the blood. One functional kidney is required for life.

Gross Anatomy of Kidneys Located next to the spinal column in the lower back Acts as a pressure based blood filter. Ureter Tube that connects the kidneys to the bladder

Gross Anatomy of the Kidneys Bladder A saclike organ that stores urine before being excreted. Urethra Tube that connects bladder to the outside of the body

Microscopic Anatomy of the Kidney Nephron – the functional, filtering units of the kidney Glomerulus Small network of capillaries Bowman’s Capsule Hollow, cup-shaped structure surrounding the glomerulus Parts of a nephron

Filtration of the blood Blood is forced under pressure through the glomerulus. Water, salt, sugars, amino acids and urea are forced out of the blood into the Bowman’s capsule. These materials are called the filtrate.

Reabsorption The filtrate moves through the Loop of Henle – a thin tube that connects the Bowman’s Capsule to the collecting duct which is surrounded by capillaries. Most of the water and nutrients are captured by capillaries.

Urine Formation Useful materials are returned to the blood. Waste materials flow to the collecting duct where they are shunted to the ureter, forming urine.

Urine Testing Most drugs are excreted by the kidneys. Tests on urine can show what drugs a patient has taken. Urine tests can also be used to detect health problems like diabetes.