Comparative Vertebrate Physiology

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Comparative Vertebrate Physiology

• Osmoregulation in non-mammalian vertebrates

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Osmoregulation

• Strategies
• Osmoconformers (plasma gt 290 mOsm)

• Osmoregulators(plasma 290 mOsm)

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Osmoregulation
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Aquatic environment

• Euryhaline
• Estuarine, salt marshes
• Stenohaline
• Most other species

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Aquatic environment

• Freshwater problems
• High amount of water intake
• Loss of body salts

Problem
Solution
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Aquatic environment

• Saltwater problems
• Prone to losing water
• Build up of body salts

Problem
Solution
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Terrestrial environment

• Problem is dehydration
• Solutions in lectures to come
• Nasal countercurrent exchange
• Water from food
• Metabolic water
• Salt glands
• Concentrate urine

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Kidney/nephron structure
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Renal processes

• Filtration
• What is filtered?
• Water and solutes
• What isnt filtered?
• Protein
• Blood cells
• Basis for filtration
• Size and charge

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Renal processes

• Reabsorption
• 99 of water solutes
• Passive and active
• Proximal tubule (60-80)

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Renal processes

• Secretion
• Water and solutes (1)

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Vertebrates

• Functional unit is the nephron
• Components
• Glomerulus
• Proximal tubule
• Loop of Henle (birds, mammals)
• Distal tubule
• Collecting duct

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Teleosts

• Freshwater
• Large glomeruli
• Dilute, copious ultrafiltrate
• Ions reabsorbed
• Dilute, copious urine

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Teleosts

• Saltwater
• Small glomeruli
• Concentrated, little ultrafiltrate
• Ions secreted
• Isotonic, little urine

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Amphibians

• Function resembles that of a FW teleost
• Nephron structure
• Dilute, copious ultrafiltrate25 - 100 ml/Kg/hr
• Ions reabsorbed (99)
• Copious, dilute urine 10 - 25 ml/Kg/hr

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Amphibians

• Most solutes are reabsorbed distally

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Reptiles

• Only have 1 kidney that is bi-lobed

Vertebrae
Kidney
Caudal junction
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Reptiles

• Nephron structure
• Lower GFR than amphibians0.5 - 20 ml/Kg/hr
• Ion reabsorption (99)
• Isotonic, little urine

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Birds

• Tri-lobed kidneys
• Comprised of lobules
• Has cortex and medulla

Cortex
Medulla
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Birds

• Nephron structure

Bird Mammalian - Type
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Birds

• Little ultrafiltrate (1 - 4 ml/Kg/hr)
• Ion and water reabsorption (99)
• Slightly hyperosmotic urine

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Urine to plasma osmolarity