Osmoregulation & Excretion PDF

Osmoregulation & Excretion Life in the Balance Regulation of Fluids facing denydration salt to...

Osmoregulation & Excretion Life in the Balance Regulation of Fluids facing denydration salt to Fresh water #20 ; flows hypotonic into ↑ in body Homeostasis is critical for life; C temperature, pH, heart rate, & much more may be regulated to stay within acceptable ranges Regulation of fluids in animals, specifically solutes & water balance = osmoregulation Different environments present different challenges to osmoregulation Saltwater vs freshwater vs land all impact water balance via osmosis Removal of waste materials (excretion) is (terrestrial : losing #20 universal, but mechanisms vary (descation ( Osmoregulation Purpose: control chemical composition of body fluids Open circulatory system = hemolymph Closed circulatory system = interstitial tissue, blood Concentration gradients can work - unit of osmosis for or against regulation Reminder: osmosis = passive transport of water across semipermeable membrane due to differences of ① concentration; can be deadly I goes to lower 2 particles) Same osmolarity = isosmotic Higher concentration = hyperosmotic - sucking towards #20 Lower concentration = hypoosmotic (whereHo sucked from Osmoregulation Con’t Osmoconformers simply attempt to be isoosmotic energy demands lower ex. mussels Exclusively found in marine animals; associated with stable conditions Osmoregulators differ from their suitable environments & thus require regulatory envir · not ↓ mechanisms must adapt Freshwater & terrestrial animals + some marine Hypoosmotic environments (freshwater) = effectively remove excess water Hyperosmotic environments (saltwater) = effectively replace lost water  osmoconformer # Stenohaline Osmoregulators Con’t cannot handle change - of tolerance narrow range Stenohaline animals cannot handle much osmolarity change (regardless of osmoconformer/ osmoregulator status) Expected in stable environments (ex: open ocean) Euryhaline animals can handle large shifts in osmolarity Expected in variable environments ( (ex: estuaries) can handle change either osmo conformers/osmo regulator Osmoregulation in Marine Environments Marine invertebrates = osmoconformers, but may regulate solutes via active transport to modify hemolymph Marine vertebrates Bony fish osmoregulate by drinking large volumes of seawater to compensate for loss to hyperosmotic seawater while removing excess salt via gills and kidneys pump out salt pee or out salt Cartilaginous fish keep body tissues slightly hyperosmotic with high levels of urea (a nitrogenous waste product); normally damaging, but TMAO protects ( proteins ↳ compound denaturing proteins that from protects Note: they are hypotonic for salt and must remove excess salt that diffuses in, but overall they are hyperosmotic, leading to small water gains (gaining to due wrea to very strong in pulling H20 Osmoregulation in Freshwater Environments only osmoregulators T Cannot osmoconform; body fluids must be hyperosmotic otic always om Solutions: Secrete excess water via urine, minimal Hyperi drinking; gain salts via diet and gill diffusion Switching between salt and freshwater environments is challenging but possible Some freshwater sources periodically dry out; a select few animals can withstand extreme desiccation via anhydrobiosis "NO HeO life" Gaimon Sull sharr C + r1 [urea] · gills > - remove salt) He · pee out #20 as waste  rats Kangaroo does not drink #zo all over · rubs oil oil gland, from gets 120 · nocturnal diet cooler/more humid burrow is Osmoregulation on Land desiccation > - #I problem Unlike most aqueous animals, terrestrial animals most serious osmoregulation risk is dehydration, so most adaptations are to minimize water loss to the drier environment Conserve water via hydrophobic coatings, behavioral adaptations, minimal evaporative surfaces Lose water via urine/feces, skin and respiratory surfaces sucked H20 out Generally replenish lost water via diet (directly or via metabolic processes) L min. pee dry poo 1. waxy barrier insect exoskeletion oily secretion  concentrated 10W 1420 ( urine changes ; blood is stable most ured impact blood stable urine is regulated to keep Energetic Concerns Regulation requires energy Osmoregulation is more costly than osmoconformity Generally, the more extreme the conditions, the more expensive the solution So, even osmoregulators try to match their environments to some degree Mechanisms of Osmoregulation How osmoregulation is achieved varies, but tends to be indirect (not controlling cell concentrations, but extracellular fluids Open circulatory systems regulate hemolymph Closed circulatory systems regulate interstitial fluid In humans, regulation is largely achieved via kidneys Generally osmoregulation and metabolic wastes are managed by the same systems (most wastes are dissolved in water for excretion), and exchanged with environments via transport epithelia (tissue specialized for movement of specific solutes) Most are tubular, extensive, and close to/connected to external surfaces More surface area = more capacity to seccrete Wastes Nitrogenous wastes are a common metabolic waste product that must be excreted following the catabolism of proteins and nucleic acids, producing ammonia (NH3), which is toxic Most animals do not excrete ammonia directly, instead converting it to something less toxic (and less water-reliant): urea or uric acid Options: Ammonia: efficient but toxic; can be directly diffused out into large volumes of water Urea: requires far less water, low toxicity, but metabolically expensive to produce Uric acid: requires almost no water, low toxicity, metabolically the most expensive Some animals use more than one system, depending on their current environment to be as efficient as possible Excretory Systems Excretory systems osmoregulate & remove metabolic wastes by producing urine from body fluids for excretion, produced via: Filtration uses pressure to push things through the membrane; materials that can pass through (water and small solutes) for filtrate Reabsorption allows for the recovery of small but useful molecules from the filtrate using active transport Secretion allows for additional molecules to be added to filtrate via active transport Types of Excretory Systems ex flatworms Protonephridia: network of dead-. end tubes throughout the organism in animals lacking a body cavity (acoelomate) Use flame bulbs with cilia to draw in fluids for filtration May be used for both waste excretion and water balance, or primarily for osmoregulation in animals able to easily diffuse metabolic wastes across body surfaces Types of Excretory Systems Con’t Metanephridia: organs ex annolids directly collecting fluids · (earthworms from the body cavity (coelom) Use a ciliated funnel to - control what draw fluid in and capillary Waste is excreted network Used for both waste removal and osmoregulation Types of Excretory Systems Con’t Malpighian Tubules: dead end tubes continuous with the digestive tract; no filtration instead wastes are secreted into tubules and moved into digestive system for excretion; reabsorption allows for high levels of water conservation  Types of Excretory Systems Con’t mammalian // chordate Kidneys: organ containing tubules fed ( via capillaries from closed circulatory system; used for waste removal and sites where osmoregulation blood > - urine In vertebrates connect to bladder via ureters and bladder empties via urethra Kidney has outer cortex and inner medulla with different solute concentrations Functional unit of the kidney is the nephron: tubing system used to produce urine from blood  ↑ blood comes in nepuron) contactws Nephron Anatomy Glomerulus: capillary ‘filter’ where blood enters via pressure, into Bowman’s capsule Filtrate moves into proximal tubule (PT), loop of Henle, and distal tubule (DT) becoming urine that moves into shared collecting duct (CT) Afferent arterioles enter glomerulus, efferent arterioles leave; peritubular capillaries surround tubules, vasa recta surround loop of Henle  Nephron Physiology filter size purpose by : Glomerulus filters primarily by size; cells, large proteins remain in the vessel system Filtrate should contain water, salts, glucose, amino acids, vitamins, nitrogenous wastes, & misc. additional small molecules PT primarily re-absorbs ions, water, nutrients by mix of passive and active transport This is where most pH regulation by excretory system occurs (by moderating bicarbonate & H+ levels) Some materials like toxins are secreted into tubule via active transport  Nephron Physiology Con’t concentrate filtrate Loop of Henle: (more salt) Descending limb highly permeable to water but not salt [concentrates filtrate] dilute Ascending limb highly permeable to salt filtrate ; but but not water (helps make interstitial fluid maintains salt con. gradient hyperosmotic, drawing out water from descending (shallow) limb) [dilutes filtrate] Cortical nephrons do not penetrate deeply into medulla; shorter loops of Henle = less concentrated urine; desert-adapted more urea = Ho animals have more juxtamedullary (deep) follow nephrons with deep loops to produce very concentrated urine Depth of Lolt shows retainment Of H20  Nephron Physiology Con’t DT continues to reabsorb salt, bicarb and secretes K+ and H+ collecting duCt CD receives filtrate from nephrons, draining toward ureter; changes in permeability to H2O and urea allow for both concentration of urine AND maintenance of hyperosmotic medulla Anti-diuretic hormone (ADH) increases permeability to water in collecting duct, concentrating urine to reduce water loss S Released in response to increases in blood osmolarity (salt consumption, dehydration) Inhibited by excess water (including in coffee, tea), alcohol Renin-angiotensin-aldosterone system (RAAS) responds to drops in blood volume or pressure, causing vasoconstriction & reducing flow to kidneys and - increasing CD permeability to salt & water; atrial natriuretic peptide (ANP) works in opposition to RAAS response - highto blood pressure - concentrate urine abs H2o before excreted => prevent 120 loss  What based on sys - type of environ.? Comparative Renal Anatomy & Physiology In mammals, proportion of cortical : juxtamedullary nephrons indicates environment More cortical = abundant water available More juxtamedullary = dehydrate risk high In birds, some juxtamedullary nephrons, but shallow even in very dehydrating environments; instead conserve water by using uric acid to produce highly concentrated urine Reptiles only have cortical nephrons, but cloacal re-absorption of water & use of uric acid minimize water loss Freshwater fish & amphibians are hyperosmotic & must produce large volumes of dilute urine; focus more on reabsorption of salts in DT Marine fish produce very little urine; kidneys are primarily for removal of ions taken in with large volumes of saltwater they must drink [supported by salt secretion in gills]