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Excreting wastes

Excreting wastes. 7.3. Introduction. Many products from metabolism harmful. Lungs eliminate CO2 Large intestine removes toxic waste digestive system Liver transforms toxins (alcohol & heavy metals) into soluble compounds that kidneys can deal with.

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Excreting wastes

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  1. Excreting wastes 7.3

  2. Introduction • Many products from metabolism harmful. • Lungs eliminate CO2 • Large intestine removes toxic waste digestive system • Liver transforms toxins (alcohol & heavy metals) into soluble compounds that kidneys can deal with. • Kidneys play crucial role in removing waste, balancing pH, and maintaining water balance.

  3. Protein metabolism • Average Canadian consumes more protein than needed. • Excess protein  carbohydrates • Nitrogen + 2H need to be removed from amino acids • Deamination: occurs in the liver. • Ammonia is a water-soluble gas: extremely toxic. • Build-up of 0.005 mg can kill a human. • Two ammonia + CO2 urea: 100 000 x less toxic

  4. Nucleic acid metabolism • Uric acid: formed by breakdown of nucleic acids. • Kidneys help in excretion

  5. Water balance • Maintained by kidneys • Humans lose approx. 2L of water a day: urine, perspiration, exhaled air. • Drop in fluid intake by 1% = thirst. 5% = pain and collapse. 10% = death.

  6. Excretion: simple • Unicellular & simple multicellular (sponge) • Every cell in contact with external environment • Wastes released directly from cell • Fluid regulation? • Ameoba & paramecium: hypertonic to freshwater: contractile vacuoles.

  7. Excretion: complex • Not every cell in contact with external environment. • Wastes need to be collected and temporarily stored. • Excretory system: cells work together to remove wastes from body or store waste until signalled to remove them.

  8. earthworm • Nephrostome: funnel-like structure: draws fluids from body cavity into tiny tubules. Collecting tubule: collects fluids from nephrostome. Bladder. Nephridiopore: small pores in which wastes are released.

  9. Grasshopper • Malpighiantububles: throughout body cavity: absorb wastes by diffusion. Wastes released into gut and eliminated as solid wastes from the anus.

  10. ..to more complex...

  11. summary

  12. Seatwork/homework • Page 345 # 1-4.

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