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Universal needs
All cells need aqueous environment
Problems:
Balance water and solutes= osmoregulation
Nitrogenous waste (from proteins) very toxic
Osmolarity: blood: 300 milliosmoles/L
• Seawater: 1,000 milliosmoles/L
Bioenergetics
Osmoconformers: must live in stable environment
Osmoregulators: use energy to maintain homeostasis
Adaptations
Ocean fish:
Gills get rid of NaCl. Active pump Cl- Na+ follows
Kidneys get rid of other solutes (very little water)
Shark:
keeps high concentration of urea.
Will actually take on water and have to urinate
Must soak shark meat in fresh water before eat it
Adaptations
Fresh water animals:
Constantly gain water and lose salts
Make large amounts of dilute urine
Gills actively transport Cl
Anhydrobiosis: life without water: some critters do this in times of dehydration: go into dormant state
Adaptations
Land animals
shell or fur or skin: waxy coat to decrease water loss by evaporation
Eat and drink water
Circulation
Insects and others: open circulation. Hemolymph baths all cells
Closed circulation: cells bathed in interstitial fluid: controlled indirectly by composition of blood.
Transport epithelium
May face the outside environment directly
OR may line channels and tubes.
Control movement of solutes.
Nitrogenous waste
Ammonia: aquatic animals… flush it away
Very soluble
Very toxic
Urea: land animals, sharks, some fish
100,000 times less toxic
Produced in LIVER from ammonia, requires energy
Uric acid: insects, snails, birds
Paste, insoluble in water
Most energy to produce
Taxonomy
Flatworms: flame bulb system: protonephridia: tubules throughout body (filtration happens at the ends)
Earthworms (annelids): metanephredia: have 2: have osmoregulation and excretory functions
Mammalian kidney
Liver: makes urea, from ammonia
Kidney – ureter - bladder – urethra
Kidney: filters blood, excretes solutes, reabsorb water
Creates hyperosmotic urine
The Sodium-Potassium pump represents a common
mechanism in maintenance of water and electrolyte
balance
Shark Rectal Gland and NaCl
SecretionOsmoregulatory Activity in Marine and
Freshwater Fish Gill
Mammalian Kidney Function
The ability to form a concentrated urine is critical to the success of animals in terrestrial habitats
The countercurrent multiplier activity of the loop of Henle in the mammalian nephron creates an osmotic gradient for water reabsorption and production of a concentrated urine
.Regulation of water and electrolyte balance is energetically demanding.
Water Conservation
Terrestrial animals must always be concerned with conserving water
The skin is one of the primary water conservation organs - it keeps the water in and prevents evaporation
The kidney, however, also prevents water loss while still filtering the blood
Regulation of Blood Volume and Concentration
The total volume of blood plasma and interstitial fluid is regulated by the degree of filtration and reabsorption in the kidney
The solute concentration and many nutrient levels are also regulated by the excretory system
The loop of Henle has three distinct regions
Descending limb: thin wall the thin-walled: highly permeable to water. Impermeable to solutes As the filtrate travels down the descending loop, water will flow from the loop into the surrounding medium via osmosis. When the filtrate reaches the hairpin turn
Lower portion of the ascending limb: highly permeable to NaCl
Ascending Limb As it travels up into the less-concentrated regions of the medulla, Na+ and Cl- will passively diffuse across the membrane. As the filtrate continues up the thick portion of the loop of Henle, Na+ and Cl- are actively pumped out of the filtrate into the surrounding medium. This requires energy, but helps to maintain the osmotic concentration gradient in the medulla.1200 mosm/L)
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