Transporting substances around the body

Transporting substances around the body

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The circulatory system

  • The heart is a muscular organ that pumps blood around the body
  • At the lungs the blood picks up oxygen and loses carbon dioxide
  • Pumped by the heart to the rest of the body
  • Arteries take blood away from the heart
  • Veins take blood back to the heart
  • Capillaries are very small blood vessels (only one cell thick)
  • Carry blood through the organs and allow the exchange of substances with all living cells in the body
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Transport in the blood

  • Red blood cells transport oxygen round the body
  • Red blodd cells contain a red pigment called haemoglobin
  • In the lungs haemoglogin combines with oxygen to form oxyhaemoglobin
  • When the cells respire, the oxyhaemoglobin breaks back down releasing oxygen for respiration
  • Red blood cells have no nucleus so more haemoglobin can be packed in
  • The blood plasma transports carbon dioxide to the lungsand the products of digestion to all living cells in the body and urea made by the liver to the kidneys where it is excreted
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Effect of exercise on the body

  • When you exercise, your muscles need more energy to contract
  • To do this you need to increase the rate at which oxygen reaches the cells
  • Also need to remove the carbon dioxide more quickly
  • Heart rate increases and blood vessels supplying blood to the muscles dilate
  • This allows more blood containing oxygen to reach the muscles
  • Breathing rate and depth of each breath also increases, this allows a greater take up of oxygen and release of co2 at the lungs
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Anaerobic respiration

  • Muscles can become fatigued after a long period of activity
  • Because of this, cells start to respire anaerobically as they can't get enough oxygen
  • This is inefficient and produces lactic acid as a waste product
  • When exercise has finished, lactic acid must be completely broken down
  • Therefore you still need to take in a lot of oxygen to do this
  • This is known as oxygen debt
  • Oxygen oxidises lactic acid into co2 and water
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Human kidney

  • The kidneys filter the blood, excreting substances you do not need and keeping those that the body needs
  • Chemical reactions in the body produce substances that are toxic eg. urea
  • Kidneys first filter the toxic substances out of the blood, then reabsorb the substances that the body needs
  • All of the toxic substances are excreted in the urine
  • Sugar and dissolved ions maybe reabsorbed against the concentration gradient. If they are, the process in which this happens is called active transport and requires energy from respiration
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Dialysis & Transplants

  • When somebody has kidney failure, a dialysis machine is used to keep them alive
  • Carries out the same function as the kidneys, the blood flows between partially permeable membranes
  • Dialysis machine is used to keep patients alive until a successful kidney transplant is carried out
  • A diseased kidney can be replaced by a healthy kidney
  • The new kidney has to have a very good tissue match
  • Immune system has to be suppressed or it is likely to reject the new kidney
  • To stop this from happening, the patient's bone marrow is treated with radiation to stop white blood cells
  • Patient will continue to take drugs to suppress the immune system
  • After the operation, the patient must be kept in sterile conditions to prevent infection
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