When you exhale on a cold day, what waste product can you see? What excretory organ

is at work?

Organs of Excretion

Excretion The process by which the body collects and removes wastes.

Includes the following organs:› Liver, Lungs, skin, and kidneys

Liver

Converts impurities and poisons in the body to less harmful substances.

Forms Urea from a harmful waste product of protein breakdown.› Urea can be safely transported to the

kidneys via blood.

Lungs and Skin

Lungs remove carbon dioxide and water when you exhale.

Sweat glands in the skin also serve an excretory function because water and urea are excreted in perspiration.

Kidneys

Diagram on Pg. 255 Filter urea and other wastes from the

blood Major organs in the excretory system Size of a fist Wastes are eliminated in urine

Kidneys

Main organ involved in water balance Hormones sent from the brain signal

the kidneys to release more or less water in urine depending on the amount of water in the body.

Your body will produce less urine on a hot day when you have sweat a lot.

Filtration of Wastes

Each kidney contains about a million Nephrons, tiny filtering units that remove wastes and produce urine.› 1st needed materials and wastes are

filtered from the blood.› Needed materials are returned to the

blood, and the wastes are eliminated from the body.

› Pg. 256 Figure 8

Filtering out Wastes

Blood enters the kidneys Blood enters a glomerulus, cluster of

tiny blood vessels in a nephron. Urea, salts, glucose, and some water

are filtered from the glomerulus into a thin-walled capsule.

Formation of Urine

The capsule around the glomerulus is connected to a long, twisting tube.

The tube is surrounded by tiny blood vessels.

As filtered material flows through the tube, the glucose, most of the water, and other needed materials pass from the tube back into the blood.

Filtration of Urine

Urea and other wastes, such as excess vitamins and harmful substances, stay in the tube.

The fluid that remains in the tube is urine.

Eventually, the urine drains into a larger tube called a ureter, which carries it from a kidney to the bladder.