IGSCE Biology - Exretion

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10 Terms

1
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What do the lungs excrete?

Carbon dioxide and water

2
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What does the skin excrete?

Water and salt by sweating

3
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What do the kidneys excrete?

Urea, water and ions from the blood. This is called urine.

4
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<p>Label this diagram</p>

Label this diagram

  1. Vena cava

  2. Left kidney

  3. Left ureter

  4. Urethra

  5. Bladder

  6. Right ureter

  7. Right kidney

  8. Aorta

    renal vein + vena cava = blue

    renal artery + aorta = red

<ol><li><p>Vena cava</p></li><li><p>Left kidney</p></li><li><p>Left ureter</p></li><li><p>Urethra</p></li><li><p>Bladder</p></li><li><p>Right ureter</p></li><li><p>Right kidney</p></li><li><p>Aorta</p><p>renal vein + vena cava = blue</p><p>renal artery + aorta = red</p></li></ol>
5
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How does the kidney carry our its role of excretion?

The kidneys filter the blood to get rid of harmful substances, particularly urea, which is produced in the liver from the breakdown of amino acids

6
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<p>Label this diagram</p>

Label this diagram

  1. Glomerulus

  2. Bowman’s capsule

  3. Proximal convoluted tubule

  4. Loop on Henle

  5. Distal convoluted tubule

  6. Collecting duct

<ol><li><p>Glomerulus </p></li><li><p>Bowman’s capsule</p></li><li><p>Proximal convoluted tubule</p></li><li><p>Loop on Henle </p></li><li><p>Distal convoluted tubule </p></li><li><p>Collecting duct</p></li></ol>
7
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Ultrafiltration

  • The blood arriving at each glomerulus is under high pressure.

  • Small molecules cross over into the kidney nephron whereas large molecules stay in the blood.

  • The fluid moves along the nephron, it is known as the glomerular filtrate

8
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Selective reabsorption

  • glucose (and other useful small molecules) mustn’t stay in the nephron and leave in the urine (it’s needed for respiration)

  • It is reabsorpted into the bloodstream from the proximal convoluted tubule

  • This happens via active transport - there are lots of mitochondria in the cells lining this part of the nephron.

9
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osmoregulation (reabsorption of water in the loop of henle)

  • the wall of the nephron is permeable to water

  • The surrounding are has low water potential and therefore the some water will leave via osmosis.

10
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Osmoregulation (hormonal control of water)

  • the body can control the water content of the blood using the kidney.

  • Special cells in the hypothalamus of the brain can detect the amount of water in the blood.

  • If you are dehydrated, the cells in the hypothalamus can cause the pituitary gland to release a hormone called the anti-diuretic hormone (ADH)

  • This then travels through the blood to the kidney where it make the walls of the nephron more permeable to water and therefore more water is reabsorpted into the blood.

  • This make the urine more concentrated (less water excreted.)

  • Opposite happen when there is a normal amount of water in the blood.