Chapter 44 Osmoregulation and Excretion Osmoregulation proccesses by which animals control colute concentrations and Excretion proccess that rids the body of toxic nitrogenous metabilites and other balance water gain loss metabolic wastes Osmoregulation balances Uptake nad Loss of Water and SOlutes Osmosis movement of water across a membrane Osmolarity osmotic pressure total solute concentration expresse as molarity o Milliosmoles liter mOsm L Isoosmotic 1 with greater concentration Hypoosmotic more dilute solution water flows in Osmotic challenges o 2 ways to maintain osmotic balance Osmoconformer isoosmotic with surroundings Marine animals Osmoregulator control internal osmolarity independent of that of its environment Can live in freshwater or trerestiral habitat Stenohaline cannot tolerate large changes in osmolarity Euryhaline can survive large osmolarity fluctuations o Marine animals Most osmoconformers osmolarity of seawater Must still use active transport for specific solutes Some many vertebrates and some invertebrates are osmoregulators Bony fish Drink lots of water then excrtete salts through kidnesy and gills Sharks and other chondrichthyes Actually have a lower osmolarity and don t drink water Osmoconromers high urea concentration and trimethalyne oxide protect proteins from damage by uresa o Freshwater Opposite problems net influx of water Drink nad pee a lot Salt replenished by food gills Salmon can do both live in ocean and the freshwater o Desiccation extreme dehydration Some aquatic invertebrates can survive by entering a dormant state anhydrosis Tardigrades water bear Must be able to keep cell membranes intact Large amount of sugar o Land animals Body coverings Insect exoskeletons Land snails have shells Keratinized skin Ways to lose water Feces and urine Across skin From surface of exchange organs Energetics of osmoregulation o 5 or more of resting metabolic rate of freshwater o 30 of resting metabolic rate of salty water organisms Transport epithelia in osmoregulation o Manage solute concentration in cells individually using an internal boyd fluid that o Transport epithelia 1 or more layers of epithelial cells specialliexed for moving particular solutes in controlled amounts in specific directions Albatross can drink salty water and drip excess salt out their beaks through bathes the cells nasal glands An animal s nitrogenous wates reflect its phylogeny and habitat Most metabolic wastes must be dissolved in water to be excrreteed Forms of nitrogenous wastes o Ammonia waste product of proteins and nucleic acid breakdown Aquatic organisms Fish0 across gill epithelia kidneys only a small amoutn Invertebrates gotten rid of across body surface o Urea nitrogenous waste made bey liver when ammonia is combined with CO2 Terrestiral and marine species Low toxicity can be safely transported stored Less water loss Takes a lot of energy to make o Uric acid nitrogenous waste excreted by insects land slnails and reptiles Nontoxic and insoluble so it is excreted as a paste with little water loss Energetically expensive Release nitrates o Gout probs with purine breakdown causing excess uric acid production Influence of evolution and environment on nitrogenous wastes o Habitat can the organism afford water loss o History o Eggs Shell less can use ammonia urea because it will diffuse out Sheleed use uric acid because it can precipitate out of solution o Diet predators eat more protein Diverse Excretory systems are variations on a tubular theme Excretory process o Urine fluid wates o Body fluid brought in contact with selectively permeable membrane o Filtration hydrostatic pressure pusehs water and small solutes thry the membrane forming a filtrate o Secretion other substances added to the filtrate by active transport water follows or leaves o Excretion the filtrate leaves the body as urine Different types of excretory systems o Protonephridia flatworms network of dead end tubules that branch thry the body Flame bulbs at the end made of a tubule cell cap cell and cilia Cilia draw water into the flame cell and into the tubule network and eventally secreted as urea High water content to maintain water homeostasis Also rotifers annelids moluscs and lancelets Function varies Freshwater flatworms used for osmoregulation as most wastes are removed through the gastrovascular cavity and mouth Parsitic flatworms isoosmotic and use it to remove nitrogenous wastes o Metaphridia excretory organs that collect fluid directly from the coelom Each worm segment has a pair immersed in the coelomic fluid and surrounded by a capillary network Cilia draw fluid into the tubule and storage bladder which opens to the outside Excretory and osmoregulatory Nitrogenous wastes remain even when the epitheliu reabsorbs most of the solutes Urine is dilute o Malpighian tubules extend from tips in the hemolyph to opening s in the digestive tract Excretory and osmoregulatory No filtration epithelium secretes wastes and solutes water follows and everything passes to the rectum where some solutes are reabsorbed and water returns to the hemolymph Uric acid is eliminated o kidneys Excretory and osmoregulatory Lots of tubules in a compact organ associated with a network of capillaries Ducts to carry urine form kidneyss Normally nonsegmented except hogfish Mammalian excretory system o Excretory organs Kidneys filtration site make urine Ureter urine leaves kidnes Urinary bladder stores urine Urethra tube for urination o Kidney Supplied with blood by renal artery and drained by renal vein Outer renal cortex Inner renal medula Renal pelvis collects urine and sends down urethra to bladder Nephron funcitonal units Cortical nephrons reach short distance into medula Juxtamedullary nephrons extend deep into medula o Critical in making hyperosmotic urine o Parts of the nephron Glomerulus ball of capillaries that are surrounded by bowman s capsule Blood pressure forcces filtrate out of the glomerulus into the bowman s capsule Processing as the fluid passes through the Proximal tubule Loop of henle ascending and descending limb Distal tubule Collecting duct transports urine to renal pelvis Afferent arteriole supplies glomerulus Efferent arteriole gets blood after glomerulus Peritubular capillaries surround the proximal and distal tubules Vasa recta hairpin shaped capillaries that serve the renal medula The nephron as a site for setpwise processing of blood filtrate Bowman s capsule is permeable to water and solt filtrate her
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