Download St. Francis Xavier University Osmoregulators

Biology 201
Dr. Edwin DeMont
Body Fluid Regulation
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Osmoregulation
Excretion of is usually associated with the
regulation of water and solute (ionic) balance
through a physiological process called
osmoregulation.
Osmosis is associated with the movement of
water down its concentration gradients.
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Osmosis
Demonstration
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Aquatic animals
Osmoregulation is an important concern for
aquatic animals – which are surrounded by water.
Large differences in the process for
marine or fresh water animals.
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Osmosis : Marine Animals
Water tends to move out of Fish
W
F
Sugar = ions
W
F
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Osmoregulators
Salt water fish
and Ammonia
Water tends to move out of Fish
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Osmosis : Fresh water Fish
Water tends to move into Fish
F
W
Sugar = ions
F
W
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Osmoregulators
Fresh water fish
and Ammonia
Water tends to move into Fish
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Invertebrate Excretory Systems
Water tends
to move into
animal.
Demonstration
Fresh water flatworm:
- Nitrogenous wastes diffuse across body surface
- Flame cells eliminate excess water
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Excretion
Excretion is the elimination of metabolic waste
products such as carbon dioxide, water,
nitrogen and ions.
Protein metabolism produces various nitrogenous wastes.
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Nitrogen Metabolism
Amino acid metabolism yields ammonia (NH3)
Ammonia alters acid-base balance as it binds to
protons and becomes ammonium ion (NH4+)
Ammonium ion can be toxic
Interferes with Na+/K+ ATPase transporters of cell
membranes by substituting for K+
1. Ammonia or ammonium ions must be highly diluted
and rapidly excreted;
2. or be converted to less toxic forms: urea or uric acid.
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Ammonia
Most aquatic animals – including most bony fishes and most
invertebrates rely on ammonia excretion, usually via gills.
This works because:
1. Water outside the animal is plentiful to dilute ammonia
2. Molecule is small and uncharged so readily penetrates most
membranes.
Most terrestrial animals do not have this option so
convert ammonia to urea or uric acid (usually in the liver)
and transport to the excretory organs.
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Urea
Urea is the primary nitrogenous waste of most adult
amphibians and mammals.
Urea is produced from two ammonium ions and a
bicarbonate ion using ATP.
Urea is 10 – 100 times less toxic than ammonia and
when it is removed takes two nitrogens per molecule.
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Uric Acid
In other terrestrial animals – insects, birds and
most reptiles uric acid is usually the primary
nitrogenous waste.
Production of uric acid is more metabolically
expensive to produce than urea but is less
toxic because it is highly insoluble, removes
four nitrogens per molecule and is excreted in
a semisolid form.
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Invertebrate Excretory Systems
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Invertebrate Excretory Systems
• Initiated by K+
secretion into lumen
• Fluid more +ve so Cl- attracted
• KCl makes tubule fluid concentrated so
water moves in via osmosis.
• Infusion of water generates a bulk
flow down the tubule
• Metabolic wastes such as uric acid secreted
and transported down system
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Urinary System
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Anatomy: Nephron
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Vertebrate Excretory Systems
Glomerulus – filtration apparatus
Walls of capillaries
contain small
perforations that as
as filters.
Blood pressure forces fluid through the slits.
The filtrate contains small molecules, ions and the primary
nitrogenous wastes either uric acid or urea.
Large proteins and blood cells do not get filtered.
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Physiology: Countercurrent
Overview
Osmosis
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