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

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

4. Metabolic waste
The type of metabolic waste depends on the environment.
Nitrogenous groups (-NH2) are removed from amino acids and nucleic acids and converted into waste.
Ammonia (NH3) which requires water but no energy to be produced.
Urea CO(NH2)2 requires energy but less water.
Uric acid (C5H4N4O3) requires the most energy.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

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

6. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

7. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

8. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

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

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

11. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

12. 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 accumulate before the urinary bladder.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

13. 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
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

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

15. Urine analysis give 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

16. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

17. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

18. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

19. Acid-base balance
Blood proteins are sensitive to pH variations. Kidneys and lungs maintain acid-base balance in the blood.
Lungs excrete CO2 that makes the blood acid
Kidneys excrete H+ via formation of ammonium ions (NH4+) and reabsorption of HCO3-.
H+ + HCO3-
H2CO3
H2O + CO2
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

20. 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 7,34.
Alkalosis occur when pH of the blood exceeds 7,45.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012

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

22. 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.
Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012