IGCSE Biology - Excretion in humans (13.1)

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The lungs, kidneys, and liver play crucial roles in excreting waste products and excess substances from the body, with each organ performing specific functions such as excreting carbon dioxide, urea, and assimilating amino acids. The structure of a kidney, including nephrons and glomerulus, facilitates the filtration and reabsorption of substances to form urine, while the liver synthesizes proteins, converts amino acids, and aids in the excretion of urea to maintain bodily balance.

Insights

  • The lungs excrete carbon dioxide, the kidneys excrete urea and excess substances, while the liver processes amino acids and eliminates waste through urea, collectively ensuring the removal of harmful substances from the body.
  • The kidney's complex structure, including nephrons with glomerulus and renal tubules, allows for filtration of blood to remove waste products while reabsorbing essential components, demonstrating a vital role in maintaining the body's internal balance through urine formation.

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Recent questions

  • What are the main organs involved in excretion?

    Lungs, kidneys, liver

  • What are the components of a kidney?

    Cortex, medulla, nephrons

  • How does the liver assist in excretion?

    Synthesizing proteins, deaminating amino acids

  • What is the function of the glomerulus in the kidney?

    Filtration of substances from blood

  • Why is urea excreted by the kidneys?

    Prevent accumulation and potential harm

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Summary

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Human Excretion: Lungs, Kidneys, Liver Functions

  • Excretion in humans involves the roles of the lungs, kidneys, and liver in removing waste products and excess substances from the body. The lungs excrete carbon dioxide, the kidneys excrete urea, excess water, and ions, while the liver plays a role in assimilating amino acids and deaminating them to form urea.
  • The structure of a kidney consists of the cortex, medulla, and nephrons, which include a glomerulus, renal capsule, renal tubule, and collecting duct. Filtration in the glomerulus removes substances like water, glucose, urea, and ions from the blood, with reabsorption of necessary components back into the blood, leading to the formation of urine.
  • The liver's role in assimilation involves synthesizing proteins from amino acids, converting excess amino acids to glucose or deaminating them to form urea. Urea is then excreted by the kidneys to prevent its accumulation, which can be harmful to the body.
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