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2 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Sylvia S. Mader Immagini e concetti della biologia

3 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 C9 - Osmoregulation and excretion

4 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Metabolic waste The type of metabolic waste depends on the environment. Nitrogenous groups (-NH 2 ) are removed from amino acids and nucleic acids and converted into waste. Ammonia (NH 3 ) which requires water but no energy to be produced. Urea CO(NH 2 ) 2 requires energy but less water. Uric acid (C 5 H 4 N 4 O 3 ) requires the most energy.

5 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Metabolic waste

6 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Osmoregulation Osmoregulation is the maintenance of the organism's water-salt content and depends on the environment. Cartilaginous fish’s blood is isotonic (equal osmotic pressure) to sea water because it contains urea.

7 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Osmoregulation Sea water is hypertonic (larger concentration of minerals) to marine bony fish’s blood. Fish must offset osmotic loss of water by drinking water constantly and pumping salt out of the gills.

8 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Osmoregulation Fresh water is hypotonic (lesser concentration of minerals) to freshwater fish’s blood. Fish must adjust for osmotic gain of water, so they don’t drink water but pump in salt at the gills.

9 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Osmoregulation Terrestrial vertebrates variously maintain the water-salt balance. Kangaroo rats defend from dehydration through osmoregulation.

10 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Osmoregulation Seagulls, reptiles and mammals have salt excreting glands that pump out salt and are regulated by the nervous system.

11 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Kidneys are complex organs In mammals kidneys are bean-shaped organs and the main components of the urinary system. Other components are: ureters, urinary bladder and urethra.

12 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Kidneys have three anatomical and functional sectors The renal cortex is the outermost region. The renal medulla located below the cortex. The renal pelvis where urine accumulates before the urinary bladder.

13 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Nephrons Nephrons (or renal tubules) are kidneys’ functional units. A nephron is composed by: Glomerular capsule Proximal convoluted tubule Loop of the nephron Distal convoluted tubule Collecting duct

14 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Urine forms in three steps

15 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Urine analysis gives health information Urinalysis gives many information about the health of the organism. The urine of a diabetic is “sweet” and frothy due to the high concentration of glucose and proteins. Urine analysis is used for identification of drugs in doping cases or drug addiction.

16 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Kidneys and water-salt balance Kidneys concentrate urine to maintain water-salt balance in mammals. Concentration is due to a countercurrent multiplier mechanism in the loop of Henle. The loop gradually increases the osmolarity of interstitial fluids.

17 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Kidneys and water-salt balance Water increasingly leaves the descending limb and collecting duct. In the ascending limb the concentration of salts in the medulla increases and urea leaks passively from the collecting duct. In the collecting duct the urine becomes hypertonic.

18 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Hormones regulate water-salt balance The hypothalamus can stimulate release of AntiDiuretic Hormone (ADH), which increases the permeability to water of collecting duct membrane. Blood volume and pressure are controlled by salt absorption. Atrial Natriuretic Hormone (ANH) Increases the loss of Na +. Hence water decreases blood volume and pressure.

19 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Acid-base balance Blood proteins are sensitive to pH variations. Kidneys and lungs maintain acid-base balance in the blood. Lungs excrete CO 2 that makes the blood acid Kidneys excrete H + via formation of ammonium ions (NH 4 + ) and reabsorption of HCO 3 -. H + + HCO 3 - H 2 CO 3 H 2 O + CO 2

20 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Acid-base balance Changing in respiration speed's rate as well as alcoholism or diabetes can lead to a variation in the blood acidity. Acidosis is the increase of the acidity (i.e. increased H + concentration), blood pH below Alkalosis occurs when pH of the blood exceeds 7.45.

21 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Artificial kidneys The artificial kidneys machine cleans up the blood from urea and salt excess. Hemodialysis

22 Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012 Dehydration and water intoxication Dehydration is due to loss of water from the cells and is treated by intake of a low-sodium solution. Excessive sweating can lead to dehydration if not balanced. Over-hydration (or water intoxication) is due to gain in water by the cells and is treated by intravenous intake of a high-sodium solution. Water intoxication can occur after consuming too much water.