Excretion in HumansCambridge IGCSE Biology: Flashcards
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Name the four main structures of the urinary system.
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- Name the four main structures of the urinary system.
- The kidneys, ureters, bladder and urethra.
- Which organ excretes carbon dioxide and how?
- The lungs excrete carbon dioxide through breathing (expiration).
- What are the two main roles of the kidneys?
- The kidneys excrete urea, excess water and excess ions in the form of urine.
- Name the two regions of the kidney visible in cross-section.
- The cortex (outer layer) and the medulla (inner layer).
- Define a nephron.
- A nephron is the functional filtering unit of the kidney responsible for urine formation.
- What substances are filtered out of the blood at the glomerulus?
- Water, glucose, urea and ions are filtered from the blood at the glomerulus.
- Which filtered substances are completely reabsorbed in the nephron?
- Glucose is completely reabsorbed in the nephron (in the proximal convoluted tubule).
- Which two substances are selectively reabsorbed in the nephron?
- Some ions and most water are selectively reabsorbed in the nephron.
- What are the three main components of urine?
- Urine contains urea, excess water and excess ions.
- Define deamination.
- Deamination is the removal of the nitrogen-containing amino group from amino acids to form urea.
- Where is urea produced and why?
- Urea is produced in the liver from excess amino acids that cannot be stored or used for energy.
- Explain the role of the liver in assimilating amino acids.
- The liver converts amino acids into proteins for use in the body (assimilation).
- Why is excretion of urea important?
- Excretion of urea is important because urea is toxic if it accumulates in the body.
- Name the tube that carries urine from the kidney to the bladder.
- The ureter carries urine from the kidney to the bladder.
- Name the tube through which urine is expelled from the body.
- The urethra carries urine from the bladder to be excreted from the body.