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Presentazione di PowerPoint
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Sylvia S. Mader
Immagini e
concetti
della biologia
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
C9 Osmoregulation
and excretion
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
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.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Metabolic waste
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
Urine forms in three steps
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
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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
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.
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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.
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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.
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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.
H+ + HCO3-
H2CO3
H2O + CO2
Lungs excrete CO2 that makes the blood acid
Kidneys excrete H+ via formation of ammonium ions (NH4+)
and reabsorption of HCO3-.
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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 7.34.
Alkalosis occurs when pH of the blood exceeds 7.45.
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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
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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.
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Sylvia S. Mader Concepts of Biology © Zanichelli editore, 2012
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