Osmoregulation = keeping water and salt balanced in the body

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Osmoregulation keeping water and salt balanced
in the body

• Question 1 why is this important
• Come up with three reasons
• Question 2 What water and salt problems do the
  following organisms face?
• Freshwater fish
• Marine fish
• Marine birds
• Marine mammals
• Question 3 How might each group solve those
  problems?

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Definitions

• Solute
• Solvent
• Osmosis
• Osmotic Pressure
• Osmolarity
• Hyperosmotic
• Hypoosmotic
• Osmoconformer
• Osmoregulator

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Solutes are dissolved particles in solution (any
type)

• Osmotic pressure depends on the number of
  solutes/unit volume (rather than chemical nature
  of solutes)

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Solutes are dissolved particles in solution (any
type)
isosmotic
(osmotic pressure is equal)
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Solutes are dissolved particles in solution (any
type)
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Water always moves from an area of low osmotic
pressure to an area of high osmotic pressure
osmotic pressure the pressure of water to enter,
given the solute concentration
Osmosis movement of water from an Area with
lower osmotic pressure to Higher osmotic pressure
Hyperosmotic (higher osmotic pressure)
Hyposmotic (lower osmotic pressure)
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Osmotic pressures are generally described in
osmolar units
Osmolarity concentration of solutes in a
solution
Osmolarity vs. Molarity
150 mMol sucrose
150 mOsm sucrose
150 mMol NaCl
300 mOsm NaCl
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Definitions

• Solute
• Solvent
• Osmosis
• Osmotic Pressure
• Osmolarity
• Hyperosmotic
• Hypoosmotic
• Osmoconformer
• Osmoregulator

Dissolved particles in a solution
What the particles are dissolved in
movement of water from an area with lower osmotic
pressure to higher osmotic pressure
the pressure of water to enter, given the solute
concentration
Concentration of solutes in a solution
Higher osmotic pressure
Lower osmotic pressure
Body fluid isoosmotic with envir.
Body fluid osmolarity regulated in opposition to
environment
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Freshwater teleosts Osmoregulators
Hyperosmotic to environment
Problems?

• water gain
• salt loss

Solutions?

• Lots of dilute urine

The gills have specialized cells CHLORIDE
CELLS they result in the active uptake of ions
across the gills

• move salt into blood

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Amphibians osmoregulators
Hyperosmotic to environment
Main osmoregulatory organ skin
Solutions?

• dilute urine

Problems?

• pump salt into body

• Gaining water

but no gills, so no chloride cells

• Losing salt

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Active transport of salts via skin

• Cl- follows passively (electric gradient)

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Marine Strategies
Cl-
Na
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Marine teleosts
Osmoregulators
(hyposmotic to environment)
Problems?

• water loss

• salt gain

Solutions?

• gain water (food, drink)

• produce little urine (isosmotic to plasma)

Chloride Cells in the gills! Actively pump ions
OUT
How?

• excrete salt

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Marine reptiles and birds
Osmoregulators Blood is hyposmotic to seawater
Cant concentrate urine
Can concentrate urine (a little bit!)
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Marine reptiles and birds
How do they get rid of huge salt load?
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Salt glands
Na mOsm
seawater 470
sea snake 620
sea turtle 690
Marine Iguana 1000-1400
gull 600-900
cormorant 500-600
petrel 900-1100
salt is excreted from the gland to outside the
body more concentrated than sea water!
mechanism is same in marine reptiles -but salt
gland is in different places
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Marine Mammals
Live in seawaterbut no chloride cells, no salt
glands?
The Mammalian Kidney
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How do mammals make concentrated urine?
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mammalian nephron
Loop of Henle

• Na is pumped out of the filtrate
• Results in osmotic gradient in the kidney ECF
• Why does this matter?

Cortex
Outer Medulla
Inner Medulla
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As filtrate passes through the collecting duct,
it loses water to the ECF
Loop of Henle
How concentrated can the filtrate become in this
organism?
300
300
Cortex
Outer Medulla
600
600
900
900
Inner Medulla
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Final urine is hyperosmoticto plasma

• up to 4X in regular terrestrial mammals
• up to 6X in marine mammals
• up to 30X in desert mammals!

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Marine Mammals
Several Adaptations
Live in seawaterbut no chloride cells, no salt
glands?
1. Long loop of henle in the kidney --concentrated
urine --less water lost with waste 2.
Diet --carnivores, eating mostly
vertebrates --vertebrates have lower
osmolarity 3. Absence of sweat glands
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TERRESTRIAL VERTEBRATES
Total Water gain and loss 2.2 0.3
1.6 0.9
In humans

• Water Loss
• Excretion
• Fecal
• Urinary
• Evaporative Water Loss
• Cutaneous
• Respiratory
• Reproduction

• Water Gain
• Food/water intake
• Metabolic water

2.2 L/day
- 1.6 L/day
0.3 L/day
- 0.9 L/day
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Nitrogenous Wastes affect Water Balance

• Water soluble
• Very toxic
• Excreted w/lots of water

• Not water soluble
• Low toxicity
• Excreted w/little water

• Water soluble
• Low toxicity
• Excreted w/less water

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Excretion
Tortoises and Turtles
of urinary nitrogen of urinary nitrogen of urinary nitrogen
Species Habitat Ammonia Urea Uric Acid Uric Acid Uric Acid
Red-eared slider Freshwater 79 17 4 4 4
Forest hinge-back tortoise Moist Terrestrial 6 61 4 4 4
Mediterranean spur-thighed tortoise Dry terrestrial 4 22 52 52 52
Texas tortoise Desert 4 3 93 93 93

• ammonia
• urea
• uric acid

Teleost fish
Amphibians
reptiles
chondrichthyes
mammals
Teleost fish
Amphibians
reptiles
Birds and reptiles
Amphibians
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Mammals

• most drink, eat foods high in water
• very concentrated urine

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How do Kangaroo Rats Cope?

• dont pant
• few sweat glands
• LONG loop of henle
• Human urine 1200 mOsm
• Kangaroo rat 5500 mOsm
• eat dry food
• dont drink!
• dont tolerate dehydration!

How?
Metabolic water
1 g glucose
0.6 g water
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35 g
54 mL oxidation water 6 mL absorbed water
16.1 mL urine, feces 43.9 mL evaporation
60 mL water
60 mL water
Urine 9x higher osmolarity than sea water!!
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Terrestrial summary

• Water in
• Food and drink
• Metabolic water
• Water out
• excretion
• Evaporative water loss
• Adaptations in the desert?
• Extended loop of henle
• Reduced evaporative water loss
• (gain in camel nose)
• High dehydration tolerance