Osmoregulation and Excretion

Damnjanović Ivana

Osmoregulation Osmoregulation balances the uptake

and loss of water and solutes

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

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 foodand by drinkingseawater

Osmotic water lossthrough gills and other partsof body surface

Excretion ofsalt ionsfrom gills

Excretion of salt ionsand small amountsof water in scantyurine from kidneys

Osmoregulation in a saltwater fish

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 ofwater and someions in food

Osmotic water gainthrough gills and other partsof body surface

Uptake ofsalt ions by gills

Excretion oflarge amounts ofwater in dilute urine from kidneys

Osmoregulation in a freshwater fish

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Body Fluid Regulation in Bony FishesCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

drinks seawater

a. Marine bony fish

does not drink

scanty amountof isotonicurine containssome salts

passive lossof waterthroughgills

salts actively

excreted by gills

passive gain ofwater through gills

large amounts of hypotonicurine contain few saltssalts actively

taken up by gills

Land Animals Land animals manage their water budgets

By drinking and eating moist foods and by using metabolic water

Waterbalance in a human

Waterbalance in akangaroo 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

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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 preventsevaporative loss ofwater at skin

Exhaled air iscooled and driedin long convolutedair passages

Oxidation offood results inmetabolic water.

Urine is themost hypertonicknown amonganimals

Fecal pelletsare dry

Excretion Gets rid of metabolic wastes Regulate solute movement between

internal fluids and the external environment

• 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?

KIDNEYS

KIDNEYS

Your kidneys are composed of 1 million cells called

nephrons

Bowman’s capsule

CapillariesKidney tubule

CapillariesCollectingduct

The nephron, the functional unit of the vertebrate kidney

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

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.

CapillaryExcretorytubule

Filtrate

Uri

ne

1

2

3

4

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

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