Osmoregulation and excretion are important physiological processes. Osmoregulation regulates solute concentrations and balances water gain and loss. Aquatic animals like marine fish and freshwater fish have different osmoregulatory challenges and adaptations. For example, marine fish drink seawater and excrete salts to balance gaining salt from their environment, while freshwater fish excrete dilute urine to avoid salt gain. Animals excrete different nitrogenous wastes depending on their habitat and phylogeny, such as ammonia, urea, or uric acid. Invertebrates like planarians, earthworms, and insects have tubular structures like flame cells, nephridia, and Malpighian

1. EXCRETION
AND
OSMOREGULATION

2. 1. OSMOREGULATION
AND EXCRETION
• Relative concentrations of water and solutes
must be maintained within fairly narrow
limits
• Osmoregulation regulates solute
concentrations and balances the gain and
loss of water.
• Freshwater animals show adaptations that
reduce water uptake and conserve solutes

3. OSMOREGULATION AND
EXCRETION
• Desert and marine animals face desiccating
environments that can quickly deplete body
water.
• Excretion gets rid of nitrogenous
metabolites and other waste products.

4. OSMOREGULATION OF
MARINE BONY FISH
• Marine bony fishes are hypoosmotic (have
less solutes/salt than) to sea water.
• They loose water by osmosis and gain salt
by diffusion and from food.
• They balance water loss by drinking
seawater and excreting salts

5. OSMOREGULATION OF
MARINE BONY FISH

6. OSMOREGULATION OF
FRESH WATER FISH
 Freshwater animals constantly take in
water by osmosis from their
hypoosmotic environment
 They lose salts by diffusion and
maintain water balance by excreting
large amounts of dilute urine
 Salts lost by diffusion are replaced in
foods and by uptake across the gills

7. OSMOREGULATION OF
FRESH WATER FISH

8. 2. WASTE PRODUCTS
 UREA
 AMMONIA
 URIC ACID
 The kinds of nitrogenous wastes
excreted depend on an animal’s
evolutionary history and habitat
 The amount of nitrogenous waste is
coupled to the animal’s energy budget

9. AMMONIA
 Form when an amino group (NH2) adds a
third hydrogen ion. = NH3.
 Ammonia is rather toxic.
 If enough water is available to wash it from
the body it can be a nitrogenous excretory
product.
 Do not require a lot of energy for
production.
 Ammonia is excreted by most fish whose
gills and skin are in direct contact with the
water of the environment.

10. UREA
 Requires a lot of energy for production of Urea.
 Carrier molecules take up carbon dioxide and 2
molecules of ammonia to form and excrete urea.
 Urea is less toxic than ammonia.
 Can be excreted as a concentrated solution. –
Important allows terrestrial animals to conserve
water.
 Sharks, frogs and mammals excrete urea as their
main nitrogenous waste.

11. URIC ACID
 Requires an extreme amount of ATP (energy) for
the production of Uric acid.
 Uric acid is not very toxic and do not dissolve in
water readily, therefore is excreted very
concentrated – to conserve water in the body.
 Uric acid is routinely excreted by insects, reptiles
and birds.

12. 3. EXCRETORY ORGANS
AMONG INVERTEBRATES
 Most animals have tubular excretory organs that
regulate the water-salt balance of the body and
excrete metabolic wastes into the environment.
 3 examples amongst invertebrates:
Planarians – use Flame cells.
Earthworms – use Nephridia.
Insects – use Malpighian tubules.
 On occasion, excretion also involves other organs,
such as the rectum in the earthworm and the gills
in crayfish.

13. PLANARIANS
(FLATWORMS)with flame cells
 Flatworms use flame cells (bud-like
outgrowths in a branched tubular excretion
system) with cilia to filter out waste and get
rid of excess water.

14. Earthworm with nephridia
Earthworms have nephridia with a ciliated
opening, called the nephridiostome, that leads
to a coiled tubule surrounded by blood
capillaries. Waste move through the tubules
and is excreted through the nephridiopore.

15. Insects with Malpighian tubules
Insects use thin tubules called Malpighian
tubules attached to the gut for excretion

16. 4. HUMAN EXCRETORY
ORGANS
 Humans use several excretory organs:
 Lungs – Carbon dioxide (waste product from
cellular respiration)
 Kidneys and bladder - Ammonia, uric acid,
excess water, excess salt and urea (Waste
products in deamination and food)
 Liver - Colorants, alcohol, poisons(Waste
products from food and drink)
 Alimentary canal - Feaces (undigested
food), cellulose.
 Skin - Excess water and salt, ammonia.

17. 5. HUMAN URINARY SYSTEM
 Consist of paired kidneys, renal artery, renal
vein, ureter, bladder and urethra.
 Each kidney is supplied with blood by a
renal artery (impure, oxygenated blood)
and drained by a renal vein (pure,
deoxygenated blood).
 Urine exits each kidney through a duct
called the urether.
 Both urethers drain into a common urinary
bladder, and urine is expelled through a
urethra.

18. HUMAN URINARY SYSTEM

19. STRUCTURE OF A KIDNEY
The mammalian kidney has two distinct regions: an
outer renal cortex and an inner renal medulla

20. STRUCTURE OF A KIDNEY

21.  REFERENCES
Biopharmaceutics and Pharmacokinetics , II edition 2005, Birla Publication
Pvt.Ltd,
https://www.slideshare.net/PinkeshPatel1/excretion-10212619, accessed in
November 2011