EXCRETORY SYSTEM

The Excretory System 1. Components and Function a. Kidneys

1.Filter the blood to remove chemicals 2. Generates about 160 gallons of filtrate per day 3. Treat the filtrate to recover valuable chemicals and water 4. Composed of subunits that have complex filtering and conditioning functions: nephrons 5. Also important in regulating blood pressure. B. Ureters: connect kidneys to bladder C. Urinary bladder: reservoir for urine 1. Lining of bladder exposed to toxins in urine D. Urethra: conduit from bladder to environment E. Nephrons 1. Tubular structures 2. Blood is filtered at one end, is treated along the way and emerges as urine 4 Filtration occurs at the glomerulus, which is a cup shaped structure, which holds a ball of capillaries. The pressure inside the capillaries generates the filtrate. 4. The filtrate passes down the tube, which is lined by tubule cells. At various points along the tube, valuable chemicals are removed and recycled for the body (glucose, amino acids), water is removed and some chemical are added to adjust the acid-base balance of the body. 5. Almost all the water in the filtrate is recovered (99%) 2. Toxic effects on the kidneys a. Tubule cells 1. Are exposed to chemicals in the circulation and in the filtrate. 2. If damaged, are unable to recycle valuable chemicals, which begin to appear in the urine. 3. Tubules dysfunction can be temporary and kidney function can recover. 4. Subtle evidence of tubular dysfunction is the appearance of proteins in the urine, which are not usually present. They may come form abnormal filtration or from damage to the tubular cells. 3. If sustained or more severe, nephrons can be lost reducing the filtration capacity. The body’s ability to excrete waste products is compromised (renal insufficiency).