Chapter 44

OSMOREGULATION: Regulates solute concentrations and balances the gain and loss of water. Based largely on controlled movement of solutes between internal fluids and the external environment
EXCRETION is the disposal of nitrogen metabolites and metabolic wastes.
Define osmoregulation and excretion.
OSMOLARITY: the solute concentration of a solution, determines the movement of water across a selectively permeable membrane
ISOOSMOTIC: Of or having the same or equal osmotic pressure
HYPOOSMOTIC: A condition in which the total amount of solutes (both permeable and impermeable) in a solution is lower than that of another solution
HYPEROSMOTIC: A condition in which the total amount of solutes (both permeable and impermeable) in a solution is greater than that of another solution.
Define osmolarity and distinguish among isoosmotic, hyperosmotic, and hypoosmotic solutions.
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●Marine invertebrates.
●isoosmotic with their surroundings
●expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
Distinguish between osmoregulators and osmoconformers
STENOHALINE: they cannot tolerate substantial changes in external osmolarity
EURYHALINE: animals can survive large fluctuations in external osmolarity
Distinguish between stenohaline and euryhaline animals
Some fishes such as cod drink large amounts of sea water and use both their gills and kidneys to rid themselves of salt. Sharks use salt, urea, TMAO, and other compunds maintained in the body fluids of the shark result in an osmolarity very close to that of sea water
Discuss the osmoregulatory strategies of marine animals.
The body fluids of freshwater animals must be hyperosmotic because animal cells cannot tolerate salt concentrations as low as those of lake or river water.
Explain how the osmoregulatory problems of freshwater animals differ from those of marine animals.
ANHYDROBIOSIS: Some aquatic invertebrates in temporary ponds lose almost all their body water and survive in a dormant state
Describe anhydrobiosis as an adaptation that helps tardigrades and nematodes to survive periods of dehydration
●land animals maintain water balance by drinking and eating moist foods and by producting water metabolically through cellular respiration
●Desert animals get major water savings from simple anatomical features and behaviors such as a nocturnal life style
●Waxy cuticle protects plants
●The body covering of most terrestrial animals helps prevent dehydration.
Describe some adaptations that reduce water loss in terrestrial animals
Osmoregulation has an energy cost because they need to control the water uptake and loss in a hypoosmotic or hyperosmotic environment.
Explain why osmoregulation has an energy cost. Describe some of the factors that affect this cost.
TRANSPORT EPITHELIA are specialized epithelial cells that regulate solute movement
●They are arranged in complex tubular networks
●Example: salt glands of marine birds, which remove excess sodium chloride from the blood
Explain the role of transport epithelia in osmoregulation and excretion
When nucleic acids and proteins are broken apart for energy or converted to carbohydrates or fats, enzymes remove the nitrogen in the form of ammonia. Many aquatic species have ammonia because it can easly pass through membranes and are readily lost by dissusion to the surrounding water.
Describe the production and elimination of ammonia. Explain why ammonia excretion is most common in aquatic species.
●Aquatic animals excrete ammonia across the body surface or epithelia into the surrounding
●The liver of of mammals and most adult amphibians convert ammonia to less toxic urea, which is carried to the kidneys, concentrated, and excreted with a minimal loss of water. Urea is at a very low toxicity.(mammals adult amphibians sharks some bony fish and turtle)
●Uric acid is eliminated as a semisolid paste with very little water loss. This is a great advantage for animals with little access to water(snails, insects, birds and reptiles)
Compare the strategies to eliminate waste as ammonia, urea, or uric acid. Note which animal groups are associated with each process
FILTRATION: pressure-filtering of body fluids
REABSORPTION: reclaiming valuable solutes
SECRETION: adding toxins and other solutes from the body fluids to the filtrate
EXCRETION: removing the filtrate from the system
Describe the key steps in the process of urine production
●found in flatworms (no circulatory system/coelom)
●simple, tubular excretory system
●PROTONEPHRIDIUM: network of closed tubules lacking internal openings that branch throughout body–smallest branches capped by cellular flame bulb
●interstitial fluid passes through flame bulb & is propelled by tuft of cilia along branched system of tubules
●urine from system empties into external environment through numerous openings called nephridiopores
●transport epithelia lining tubules absorb salts before fluid exits body
●also found in rotifers, some annelids, larvae of mollusks, and lancelets
Describe how a flame-bulb (protonephridial) excretory system functions
1. Internal opening.
2. Collecting tubule.
3. Bladder.
4. External opening.
Flame bulb cell on the ends of the tubules have cilia and a cap cell. Interstitial fluid filters through membrane where cap cell and tubule all interlock.
Explain how the metanephridial excretory tubule of annelids functions. Compare the structure to the protonephridial system.
Salt, water, and nitrogenous wastes leave through the malpighian tubules. Hemolymph also filters through the tubules. Feces and urine leave through the rectum where there is reabsorption of water ions and valuable organic molecules.
Describe the Malpighian tubule excretory system of insects
Using a diagram, identify and state the function of each structure in the mammalian excretory system
Figure 44.14 a-c
The Loop of Henle in CORTICAL Nephrons only extends into the Renal Cortex.
The Loop of Henle in JUXTAMEDULLARY Nephrons extends into the Renal Medulla
Distinguish between cortical and juxtamedullary nephrons
Using a diagram, identify and describe the function of each region of the nephron
● blood pressure forces fluid (water, salts, urea, & other small molecules) from glomerulus into lumen of Bowman’s capsule
● porous capillaries and podocytes (specialized cells of the capsule) nonselectively filter out blood cells and large molecules
● any molecules small enough to be forced through capillary wall enters nephron tubule
● filtrate at this point contains mixture of glucose, salts, vitamins, nitrogenous wastes, & small molecules in is similar to blood plasma
● filtrate passes through proximal tubule, loop of Henle, distal tubule, and empties into collecting duct
● filtrate joined by some substances transported across the tubule epithelium from surrounding interstitial fluid as it moves through nephron tubule–adds plasma solutes to filtrate
● proximal & distal tubules most common sites of secretion
● secretion very selective process involving both passive and active transport–EXAMPLE: controlled secretion of H+ helps maintain constant body fluid pH
● is selective transport of filtrate substances across excretory tubule epithelium from filtrate back to interstitial fluid
● reclaims small molecules essential to body
● occurs in proximal tubule, distal tubule, loop of Henle, and collecting duct
● nearly all sugar, vitamins, organic nutrients are reabsorbed
● in mammals and birds, water is also reabsorbed
Describe and explain the relationships among the processes of filtration, reabsorption, and secretion in the mammalian kidney.
Reabsorption of water continues as the filtrate moves into the descending limb of the water of henle. Here numeroue was channels formed by aquaporin proteins make the transport epithelium freely permeable to water
Explain how the loop of Henle enhances water conservation by the kidney by functioning as a countercurrent multiplier system.
● Beaver has a very short loop
● Human has a medium loop
● Kangaroo rat has a very long loop
● Birds have shorter loops of Henle but conserve water by excreting uric acid instead of urea
● Reptiles have only cortical nephrons but also excrete nitrogenous waste as uric acid
Mammals that inhabit dry environments have long loops of Henle, while those in fresh water have relatively short loops
Describe variations in nephron structure and function that equip the kidneys of different vertebrates for osmoregulation in various habitats.
Explain the significance of the juxtamedullary nephrons of birds and mammals

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