Osmoregulation and excretion

1. Osmoregulation and Excretion
Damnjanović Ivana

2. Osmoregulation
Osmoregulation balances the uptake
and loss of water and solutes

3. A balancing act
Physiological systems operate within a fluid environment
Water and solutes must be maintained within narrow limits –
despite strong challenges from an animal’s external environment
Osmoregulation:
Freshwater animals =>
dilution of body fluids
Desert and marine animals
=> desiccation
Excretion:
Protein metabolism =>
toxic ammonia Albatross can drink seawater with no ill
effects

4. 
Marine bony fishes are hypoosmotic to
sea water
− And lose water by osmosis and gain salt
by both diffusion and from food they eat

These fishes balance water loss
− By drinking seawater
Gain of water and
salt ions from food
and by drinking
seawater
Osmotic water loss
through gills and other parts
of body surface
Excretion of
salt ions
from gills
Excretion of salt ions
and small amounts
of water in scanty
urine from kidneys
Osmoregulation in a saltwater fish

5. 
Freshwater animals maintain water balance
− By excreting large amounts of dilute urine

Salts lost by diffusion
− Are replaced by foods and uptake across the
gills
Uptake of
water and some
ions in food
Osmotic water gain
through gills and other parts
of body surface
Uptake of
salt ions
by gills
Excretion of
large amounts of
water in dilute
urine from kidneys
Osmoregulation in a freshwater fish

6. 6
Body Fluid Regulation in Bony Fishes
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
drinks seawater
a. Marine bony fish
does not drink
scanty amount
of isotonic
urine contains
some salts
passive loss
of water
through
gills
salts actively
excreted by gills
passive gain of
water through gills
large amounts of hypotonic
urine contain few salts
salts actively
taken up by gills

7. Land Animals

Land animals manage their water budgets
− By drinking and eating moist foods and by
using metabolic water Water
balance in
a human
Water
balance in a
kangaroo rat
Ingested
in food
Ingested
in food
Ingested
in liquid
Derived from
metabolism
Derived from
metabolism
Water
gain
Feces
Urine
Evaporation
Feces
Urine
Evaporation
Water
loss

8. 8
Adaptations of a Kangaroo Rat
to a Dry Environment
.
© Bob Calhoun/Bruce Coleman, Inc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Animal fur prevents
evaporative loss of
water at skin
Exhaled air is
cooled and dried
in long convoluted
air passages
Oxidation of
food results in
metabolic water.
Urine is the
most hypertonic
known among
animals
Fecal pellets
are dry

9. Excretion

Gets rid of metabolic wastes

Regulate solute movement between
internal fluids and the external
environment

10. • The most important waste products are CO2,
nitrogen compounds, and salts.
• CO2 – produced during cellular respiration
(in addition to water)
• Nitrogen compounds – (ammonia, urea, and
uric acid) produced by the breakdown of amino
acids (protein digestion)
• Salts – produced by metabolism
What is Excretion?

11. KIDNEYS

12. KIDNEYS

Your kidneys are composed of
1 million cells called
nephrons

14. Bowman’s
capsule
Capillaries
Kidney
tubule
Capillaries
Collecting
duct
The nephron, the functional unit of the vertebrate kidney

15. Nephrons and associated blood vessels are the
functional units of the mammalian kidney
-Renal artery and vein – high blood supply (1,100 - 2,000 L
through a pair of kidneys/day)
-Urine exits through ureter to urinary bladder and urethra,
regulated urination
-Renal cortex, medulla, pelvis

16. Excretory Processes

Most excretory systems
− Produce urine by refining a filtrate derived
from body fluids
Filtration. The excretory tubule collects a filtrate from the blood.
Water and solutes are forced by blood pressure across the
selectively permeable membranes of a cluster of capillaries and
into the excretory tubule.
Reabsorption. The transport epithelium reclaims valuable
substances from the filtrate and returns them to the body fluids.
Secretion. Other substances, such as toxins and excess ions, are
extracted from body fluids and added to the contents of the excretory
tubule.
Excretion. The filtrate leaves the system and the body.
Capillary
Excretory
tubule
FiltrateUrine
1
2
3
4

17. 
Key functions of most excretory
systems are
− Filtration, pressure-filtering of body
fluids producing a filtrate
− Reabsorption, reclaiming valuable
solutes from the filtrate
− Secretion, addition of toxins and
other solutes from the body fluids to
the filtrate
− Excretion, the filtrate leaves the
system

18. What kinds of animals have
the most efficient kidneys?
• Desert animals must be
able to conserve
moisture
• Most terrestrial animals
must drink fresh water
often; however the
kangaroo rat does not
need to drink water very
often – its kidneys
absorb every little drop
of water