Copyright © 2009 Pearson Education, Inc.  The urinary system regulates many aspects of homeostasis including the volume, pH, pressure, and composition of the blood  The urinary system eliminates nitrogenous wastes, water, salts and excess ions in the urine  The kidneys are the primary organs of the urinary system

Copyright © 2009 Pearson Education, Inc. Organs Eliminate Waste  Kidneys are responsible for excreting urine  Nitrogen-containing wastes  Water  Carbon dioxide (as HCO 3- )  Inorganic salts and hydrogen ions  Urine travels from the kidneys down the ureters to the urinary bladder, where it is temporarily stored until it is excreted through the urethra

Copyright © 2009 Pearson Education, Inc. By Producing Urine, the Kidneys Maintain Homeostasis  Each kidney has three regions 1.Renal cortex 2.Renal medulla 3.Renal pelvis (where urine collects before leaving the kidney)  The nephron is the functional unit of the kidney responsible for the formation of urine

Copyright © 2009 Pearson Education, Inc. The Nephron  The nephron performs three functions 1.Glomerular filtration 2.Tubular reabsorption 3.Tubular secretion

Copyright © 2009 Pearson Education, Inc. The Kidneys  The kidneys help regulate the pH of the blood by  Reabsorbing bicarbonate ions and returning them to the blood  Removing excess hydrogen ions from the blood

Copyright © 2009 Pearson Education, Inc. The Kidneys  The nephrons that extend into the renal medulla are responsible for conserving water  They regulate the concentration of the filtrate as it passes through the tubules

Copyright © 2009 Pearson Education, Inc. Kidney Function and Hormones  Antidiuretic hormone (ADH)  Regulates the amount of water reabsorbed by the distal convoluted tubules and collecting ducts of the nephrons  Aldosterone  Increases reabsorption of sodium by the distal convoluted tubules and collecting ducts in response to blood pressure

Copyright © 2009 Pearson Education, Inc. Kidney Function and Hormones  Atrial natriuretic peptide (ANP)  Released from the heart in response to increased blood volume and pressure  Relieves both of these conditions with increased urine output and by inhibiting ADH and rennin

Copyright © 2009 Pearson Education, Inc. Kidney Function and Hormones  The kidneys have two homeostatic functions not related to the urinary system  They release erythropoietin  A hormone that stimulates the production of red blood cells  They transform vitamin D into its active form  Promotes the absorption and use of calcium and phosphorus by the body

Copyright © 2009 Pearson Education, Inc. Dialysis and Transplant Surgery Help When Kidneys Fail  Renal failure  Can be acute or chronic  Results in irreversible decline in the rate of glomerular filtration  Kidney transplants provide the recipient with a healthy kidney  Hemodialysis  Use of artificial devices to cleanse the blood

Copyright © 2009 Pearson Education, Inc. Bacteria Can Cause Urinary Tract Infections  Microorganisms can enter the urethra from the rectum or as STDs and cause urinary tract infections (UTIs)  The most common cause of UTIs in women is E. coli

Copyright © 2009 Pearson Education, Inc. Bacteria Can Cause Urinary Tract Infections  UTIs include  Urethritis  Infection of the urethra  Cystitis  Infection of the bladder  Pyelonephritis  Infection of the kidneys  Each is serious and should be treated immediately