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David.Rascon44-45.pdf - Coggle Diagram

- - - - Definition: Balance of water and solutes in the body.
      - Driven by concentration gradients across plasma membranes.
      - Occurs via controlled movement of water and solutes.
      - Key Process: Osmosis (water moves from hypoosmotic
      - Osmolarity: moles of solute / liter of solution
        
        Human blood ≈ 300 mOsm/L
        Seawater ≈ 1,000 mOsm/L
    - - Stenohaline: tolerate only narrow salinity ranges.
        Euryhaline: survive broad salinity changes
    - - Marine Animals
        
        Marine invertebrates – osmoconformers, active ion transport.
        
        Marine bony fishes – lose water → drink seawater → excrete salts via gills/kidneys.
        
        Sharks/chondrichthyans – retain urea + TMAO → slightly hyperosmotic → gain water osmotically.
      - Freshwater Animals
        
        Gain water by osmosis → excrete large volumes of dilute urine.
        
        Replenish salts via food and active uptake through gills.
        
        Salmon: switch between freshwater and marine regulation via hormone cortisol
      - Terrestrial Animals
        
        Water loss → urine, feces, evaporation.
        Adaptations: waxy cuticle, keratinized skin, nocturnal habits, metabolic water.
      - Anhydrobiosis
        
        “Life without water.”
        
        Tardigrades – can dehydrate > 95%, survive for years.
        
        Trehalose sugar protects membranes.
        
        Modern use: dry storage of biological materials.
  - - - Excretion = removal of nitrogenous & other metabolic wastes.
      - Linked to osmoregulation because waste must dissolve in water.
      - Impacts an animal’s water balance and energy budget.
    - - Ammonia
        
        Highly toxic, interferes with oxidative phosphorylation.
        
        Requires lots of water for dilution.
        
        Common in aquatic species (bony fish, many invertebrates).
        
        Diffuses easily across membranes.
        
        Energy cost: very low.
      - Urea
        
        Produced by combining ammonia + CO₂ in the liver (urea cycle).
        
        Low toxicity, high solubility.
        
        Requires some water for excretion.
        
        Common in mammals, amphibians, sharks, some bony fish.
        
        Energy cost: moderate (requires ATP).
      - Uric Acid
        
        Least toxic, insoluble in water → excreted as semisolid paste.
        
        Very energy-intensive to produce (highest ATP cost).
        
        Found in birds, reptiles, insects, land snails.
        
        Advantage: conserves water; useful in dry habitats.
    - - Natural selection shapes waste type based on habitat water availability
        
        Aquatic turtles: ammonia + urea
        
        Terrestrial turtles: uric acid
        
        Birds/reptiles: uric acid in shelled eggs (non-leaky → solid waste prevents poisoning).
        
        Mammalian embryos: wastes removed by mother’s blood.
      - Endotherms vs. Ectotherms
        
        Endotherms → higher metabolism → more nitrogen waste.
      - Diet impact
        
        Carnivores/predators: more protein → more nitrogen waste.
        Herbivores: less nitrogenous output.
  - - - Excretory systems across species all rely on tubular networks.
      - Tubules provide large surface area for exchange of solutes & water.
      - Each system represents an evolutionary adaptation of the same core design.
    - - Protonephridia – Flatworms
        
        Structure: Network of dead-end tubules with flame bulbs (cap cell + tubule cell).
        
        Function: Cilia draw interstitial fluid → filter it → release dilute urine through body openings.
        
        Main Role: Osmoregulation (especially in freshwater flatworms).
      - Metanephridia – Earthworms
        
        Structure: One pair per segment; open-ended funnel (nephrostome) → tubule → bladder → external pore.
        
        Fluid Source: Collects coelomic fluid from adjacent segment.
        
        Function:
        
        Reabsorbs solutes into capillaries.
        Produces dilute urine to offset water gained osmotically.
      - Malpighian Tubules – Insects & Terrestrial Arthropods
        
        Structure: Outpocketings of the digestive tract; no pressure filtration.
        
        Process:
        
        tubules secrete solutes & nitrogenous wastes from hemolymph into tubule lumen.
        
        Water follows osmotically.
        
        In the rectum → solutes & water reabsorbed, uric acid excreted as dry paste.
      - Kidneys – Vertebrates & Some Chordates
        
        Function: Central organ for osmoregulation & excretion.
        
        Structure: Highly organized tubule networks + capillaries.
        
        Associated Structures: Ducts → ureter → bladder → urethra
  - - - Proximal Tubule (Cortex)
        
        Reclaims:
        
        NaCl (salt) → active transport out.
        
        Water → follows salt by osmosis.
        
        Glucose, amino acids, K⁺, bicarbonate (HCO₃⁻), vitamins → reabsorbed.
        
        Secretes into filtrate:
        
        H⁺ (acid)
        
        Drugs / toxins from blood (active secretion).
        
        Ammonia (NH₃) is made and released to neutralize excess H⁺ → helps pH balance.
      - Descending Limb of Loop of Henle
        
        Permeable to water ONLY (lots of aquaporins).
        
        Not permeable to salt.
        
        Surrounding medulla is very salty
      - Ascending Limb of Loop of Henle
        
        Permeable to salt, NOT water.
        
        Thin segment: salt (NaCl) diffuses out passively.
        
        Thick segment: salt (NaCl) pumped out actively using ATP.
        
        Result: filtrate becomes more dilute as it rises because salt leaves but water can’t follow.
        
        This salt export is what helps build the salty gradient in the medulla.
      - 4.Distal Tubule (Cortex)
        
        Fine-tunes ion balance and pH.
        
        Reabsorbs: NaCl, bicarbonate (HCO₃⁻), water.
        
        Secretes: K⁺ and H⁺ into the filtrate.
        
        Helps control blood acidity and salt levels.
      - Collecting Duct (Cortex → Deep Medulla)
        
        Under hormonal control:
        
        Can insert aquaporins to reabsorb more water if body needs to conserve it.
        
        Outer regions:
        
        Water leaves filtrate (osmosis).
        Some salt actively pumped out.
        
        Inner medulla:
        
        Becomes permeable to urea, which diffuses out and helps keep the inner medulla extremely hyperosmotic.
        
        Result when conserving water
        
        Urine becomes very concentrated (hyperosmotic) to body fluids.
  - - - Trigger: high osmolarity (too salty blood / not enough water)
      - Fix: reabsorb WATER
      - Effect: ↓ urine volume, ↑ urine concentration
    - - Trigger: low blood pressure / low blood volume
      - Fix: reabsorb SALT + water, constrict vessels
      - Effect: ↑ blood volume, ↑ blood pressure
    - - Trigger: high blood pressure / stretched atria
      - Fix: excrete SALT + water, block RAAS
      - Effect: ↓ blood volume, ↓ blood pressure