Osmoregulation and Excretion Flashcards
Osmoregulation
Regulation of solute concentrations and balance of gains and losses of water
Excretion
Getting rid of nitrogenous metabolites and other waste products
Osmolarity
Solute concentration of a solution
Determines movement of water across a selectively permeable membrane
Osmoconformers
Some marine animals (mostly invertebrates)
Isoosmotic with surroundings and don’t regulate their osmolarity
Osmoregulators
Expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
Anhydrobiosis
Life without water
Tardigrades: organisms that can live without water for a long time
Stenohaline
Animals that cannot tolerate substantial changes in external osmolarity
Humans, insects, most fish, birds, mammals
Euryhaline
Animals that can survive having large fluctuations in external osmolarity
Barnacles: euryhaline osmoconformers
Salmon: euryhaline osmoregulators
Transport epithelia
Epithelial cells that are specialized for moving solutes in specific directions
Typically arranged in complex tubular networks
Example: nasal glands of marine birds, which remove excess NaCl from blood (salt is secreted through nose and runs down beak)
3 main waste products
Ammonia (NH3)
Urea
Uric acid
Ammonia as waste
Fish Excrete small amounts Need access to large amounts of water Low metabolic cost to produce Release this across whole body surface or through gills
Urea as waste
Mammals and most adult amphibians
Circulatory system carries this to the kidneys, where it is excreted
More energetically expensive than NH3, but requires less water
Uric acid as waste
Insects, land snails, many reptiles, birds
Nontoxic: doesn’t harm embryos in eggs
Isn’t readily water soluble
Can be excreted as paste with little water loss
More energetically expensive to produce than urea
Key functions of most excretory systems
Filtration: filtering of body fluids
Reabsorption: reclaiming valuable solutes
Secretion: adding nonessential solutes and wastes from the body fluids to the filtrate
Excretion: processed filtrate containing nitrogenous wastes is released from body
Protonephridia
Excretory system in flatworms
Network of dead-end tubules connected to external openings
Smallest branches of network are capped by cellular units called flame bulbs
Flame bulb contains cillia that direct fluid down tubules
Metanephridia
Excretory system in segmented worms
Each segment has pair of these
Consist of tubules that collect coleomic fluid and produce dilute urine for excretion
Malpighian tubules
Excretory system in terrestrial arthropods
Remove nitrogenous wastes from hemolymph and function in osmoregulation
Insects produce mainly uric acid: adaptation to terrestrial life
Excretory organs of humans
Renal artery and vein connect to kidney
Kidney -> ureter -> urinary bladder -> urethra
Flow of fluid through kidneys
Renal cortex (outermost layer) -> renal medulla (chambers between cortex and pelvis) -> renal pelvis (main chamber in middle) -> ureter (tube connecting pelvis with bladder)
Nephron types
Cortical nephron: mainly in renal cortex, but a bit in renal medulla
Juxtamedullary nephron: extend from renal cortex into renal medulla
Flow of fluid through nephron
Arteriole from renal artery -> Glomerulus -> Bowman’s capsule -> proximal tubule -> loop of Henle -> distal tubule -> collecting duct
Bowman’s capsule
Blood is filtered out of Glomerulus into here
Filtrate produced contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
Proximal tubule
Reabsorption of ions, water, and nutrients
As filtrate passes through, materials to be excreted become more concentrated
Molecules are transported actively and passively from filtrate to interstital fluid to capillaries
Loop of Henle
Descending: reabsorption of water into interstitial fluid through channels formed by aquaporin proteins; filtrate becomes increasingly concentrated
Ascending: salt diffuses from tubule into interstitial fluid; filtrate becomes increasingly dilute
Distal tubule
Regulates K+ and NaCl concentrations of body fluids
Controlled movement of ions contributes to pH regulation
Collecting duct
Carries filtrate through medulla to renal pelvis
Reabsorption of solutes and water to interstitial fluid
Some urea is pulled out, but most is excreted
Urine is hyperosmotic to body fluids
Antidiuretic hormone (ADH)
Makes collecting duct more permeable to water
Increase in osmolarity triggers release of this, which helps to conserve water
Osmolarity of urine is regulated by hormonal and nervous control
Temporarily increases number of aquaporins in membrane of collecting ducts
Diuretic
Inhibits the release of ADH: flush water out rather than reabsorb it
