gas exchange 1

• Gas exchange


  The 'swapping' of gasses - absorbing oxygen into the blood and removing carbon dioxide from the blood
• Diffusion


  The overall movement of particles of gas or liquid from an area of higher to lower concentration
• Breathing/Ventilation


  The physical process which moves air into and out of the lungs
• Respiration


  The chemical process which occurs in all cells to release energy from glucose
• Gas exchange system


  • Allows oxygen to travel into cells for respiration
  • Removes carbon dioxide, a waste substance made by respiration
• Parts of the gas exchange system


  • Trachea
  • Bronchus
  • Bronchiole
  • Alveoli
  • Intercostal muscles
  • Diaphragm
• Trachea


  Also called the windpipe, it runs from the mouth down towards the lungs and is lined with rings of cartilage to keep it open
• Bronchus


  The trachea splits into a left and right bronchus, each leading to a lung
• Bronchiole


  Each bronchus splits again and again into thousands of smaller tubes that take air deeper into the lungs
• Alveoli


  Tiny air sacs at the ends of bronchioles where oxygen moves into the blood and carbon dioxide moves out
• Intercostal muscles


  Muscles that run between the ribs and form the chest wall, contracting and relaxing with the diaphragm during breathing
• Diaphragm


  A dome-shaped, flat sheet of muscle under the lungs that contracts and relaxes with the intercostal muscles during breathing
• How oxygen travels into blood


  1. Air is breathed into the lungs through the trachea

  2. The trachea divides into bronchi

  3. The bronchi divide into bronchioles

  4. The bronchioles end in alveoli

  5. Alveoli are surrounded by capillaries, allowing oxygen and carbon dioxide exchange
• Alveoli


  • Provide an efficient exchange surface adapted for gas exchange
  • Absorb oxygen needed for respiration into the blood
  • Transfer carbon dioxide produced by respiration from the blood into the lungs and air
• Adaptations of alveoli


  • Very large surface area
  • Only one cell thick for short diffusion distance
  • Lots of blood capillaries for good blood supply
  • Moist surfaces for gases to dissolve and pass through cell membrane
• Ventilation


  1. Diaphragm contracts and moves downwards during inhalation

  2. Diaphragm relaxes and moves upwards during exhalation

  3. Intercostal muscles contract, moving ribs upwards and outwards during inhalation

  4. Intercostal muscles relax, letting ribs move downwards and inwards during exhalation

  5. Volume of ribcage increases during inhalation, decreases during exhalation

  6. Pressure inside chest decreases below atmospheric during inhalation, increases above atmospheric during exhalation

  7. Air moves into lungs during inhalation, out of lungs during exhalation
• Types of respiration


  • Aerobic respiration
  • Anaerobic respiration
• Respiration


  A chemical reaction which occurs in all living cells, releasing energy from glucose
• Respiration is not the same as breathing or ventilation
• Aerobic respiration


  Glucose + oxygen → carbon dioxide + water
• Aerobic respiration


  • Occurs with oxygen
  • Releases more energy but more slowly
• Anaerobic respiration


  Glucose → lactic acid
• Anaerobic respiration


  • Occurs without oxygen
  • Releases less energy but more quickly
• During vigorous exercise


  Anaerobic respiration occurs as cells may not have enough oxygen for aerobic respiration
• Anaerobic respiration produces lactic acid which causes pain and tiredness, leading to cramps
• After vigorous exercise, people continue to breathe deeply and quickly for a short period to replenish oxygen and convert lactic acid to carbon dioxide and water
• This is called excess post-exercise oxygen consumption (EPOC), previously known as 'oxygen debt'