The body system that collects wastes produced by cells and removes(excretes) the wastes from the body

The Kidneys… Major organs of Excretory System Eliminate urea, excess water, & other waste Urea: chemical that comes from the breakdown of proteins Act as filters as blood flows through Wastes are eliminated in urine, a watery fluid produced by the kidneys human-hormone.com

Excretion of urine… Urine flows from kidneys through two narrow tubes, called ureters, into the urinary bladder. In this saclike muscular organ, urine is stored until the need to urinate. Urine then flows from the body through a small tube, called the urethra.

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The Filtering Process… Nephrons: tiny filtering structures that remove wastes from blood and produce urine About one million in each kidney Stages of Urine: Wastes & needed material like glucose are removed from the blood Much of the needed material is returned to the blood

Filtering out Waste… Blood flows through smaller & smaller arteries Capillary clusters in a nephron Urea, glucose, other chemicals, & some water move from the blood into a hollow capsule Blood cells and most protein molecules remain in capillary clusters

Formation of Urine… Filtered waste in capsules pass through a long tube Needed material is reabsorbed into the blood Urea & other wastes remain in the tube = urine

Analyzing Urine… Normally urine contains almost no glucose or protein Glucose = diabetes Protein = kidneys are not functioning properly

Water Balance… Kidneys maintain homeostasis by regulating water Hot/warm days – more water is reabsorbed producing less urine Cold/cool days – less water is reabsorbed producing more urine

Other Organs & Excretion… Not all wastes are removed by the kidneys Lungs: exhale carbon dioxide & some water vapor Skin: perspiration Liver: produces urea and bile