Osmoregulation and Excretion - PowerPoint

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					Osmoregulation and Excretion
          Ch. 44; pp. 922-931

 • Osmosis and Osmoregulation
 • Osmoregulation in bony fish

 • Nitrogenous wastes

 • Salt excreting glands

 • Excretory Systems
Osmosis




      Fig. 7.12
Body fluid osmotic concentrations




                      Fig. 44.1
                Osmoregulation
Advantages
  Osmoregulators can live in a wide variety of habitats:
  marine, estuaries, freshwater, land.


Disadvantages
  Osmoregulation is energetically costly, depending on
  how different the animal’s internal osmolarity is from
  the environment, how permeable the animal’s surfaces
  are to water and ion movement, and how costly it is to
  pump ions across membranes.
                                          Types of Osmoregulators
                      1600

                      1400
                                 Hyperosmotic regulator
Body Fluid, mOsm/Kg




                      1200
                                                                                       Shore Crab
                      1000                                                             Decorator crab
                                                                                       Isosmotic Line
                      800
                                                      Osmoconformer                    Freshwater Fish
                      600                                                              Marine Fish
                                                                                       Fiddler Crab
                      400
                                                     Hypo-osmotic regulator
                      200

                        0
                             0     200   400   600   800   1000   1200   1400   1600
                                         External Medium, mOsm/Kg
    Reptiles, Birds, Mammals
                    Amphibia
            Teleost Fish FW
            Teleost Fish SW
                  Sharks FW
                 Sharks SW
           Invertebrates FW
           Invertebrates SW
                               0   200   400   600   800 1000 1200
                                    Body Fluid, mOsm/Kg
                                     Ions      Urea & TMAO
• Freshwater animals must regulate their internal osmolality above
  ambient levels.
• Marine inverts are often osmoconformers since they experience little
  environmental change (they are isoosmotic to their environment).
    Reptiles, Birds, Mammals
                    Amphibia
            Teleost Fish FW
            Teleost Fish SW
                  Sharks FW
                 Sharks SW
           Invertebrates FW
           Invertebrates SW
                               0   200   400   600   800 1000 1200
                                    Body Fluid, mOsm/Kg
                                     Ions      Urea & TMAO
• Marine sharks are isoosmotic but not isoionic.
• Marine teleost fish are hypoosmotic and hypoionic compared to
  seawater.
 Osmoregulation in marine and freshwater fish
   Marine fish face two problems: they tend to lose
   water and gain ions.




Fig. 44.3
 Osmoregulation in marine and freshwater fish
   Freshwater fish face two problems: they tend to
   lose ions and gain water.




Fig. 44.3
Water balance: a comparison of two
       terrestrial mammals




    Fig. 44.16
Salt Excreting Glands
• Birds, although they have loops of
  Henle, cannot make a very
  concentrated urine - their loops
  are fairly short.

• Marine birds and reptiles (which
  cannot make a concentrated urine)
  have evolved extrarenal routes of
  salt excretion.

• Birds use nasal glands that release
  salt excretions into the nasal
  passages.

• Sea turtles have modified tear
  ducts that secrete salt into the
  orbit of the eye.
                                        Fig. 44.12
Nitrogenous Wastes
• Ammonia is quite toxic
  but can be easily excreted
  into water.

• Because of its low
  toxicity, urea is used by
  many terrestrial species.
  Less water is needed for
  its excretion.

• Uric acid is the least toxic.
  Because it has low water
  solubility, it is used by
  terrestrial animals that
  have more severe water
  conservation problems.
                                  Fig. 44.13
               Excretory Systems

Dispose of metabolic wastes and regulate body fluid
composition.

Rely on a system of tubes lined with transport epithelia.

Tubes are in close contact with the circulatory system.
                  Excretory Processes
Initial fluid collection
involves filtration across a
selectively permeable
membrane.

Valuable solutes are
selectively reabsorbed via
active transport.

Wastes can be actively
secreted into the filtrate.

The filtrate is excreted
                                        Fig. 44.9
from the body.
              Excretory Systems

Protonephridia in flatworms
Dead-end tubules that lead to
a opening in the body wall.




                        Fig. 44.10
               Excretory Systems

Metanephridia in earthworms
Long tubes surrounded by
capillaries in each segment.

The nephrostome is in one
segment and the tubes are in
the next segment.

The tubes lead to an opening
in the body wall.
                      Fig. 44.11
               Excretory Systems

Malpighian tubules in insects
Long tubes whose tips are in
hemolymph sinuses and that
open into the digestive tract.

Valuable solutes are
reabsorbed in the rectum.



                Fig. 44.12
      The Mammalian Kidney
• Mammals and birds are the only vertebrates that
  can make a urine more concentrated than their
  body fluids.

• Anatomical arrangement of the nephrons is a
  critical part of this capability.
Mammalian Kidney - Overview




               Fig. 44.13