Gas Exchange

• Levels of organisation from smallest to largest

  • Cell
  • Tissue
  • Organ
  • Organ system
  • Multicellular organism
• Organ system

  • The respiratory system is responsible for oxygen diffusing into the body and carbon dioxide diffusing out. The circulatory system transports substances around the body in blood. The reproductive system is needed to create new organisms.
• Draw and label a diagram of an animal cell
• What gas do we need to breathe in?
• What gas do we need to breathe out?
• What organ does gas exchange take place in?
• What structure protects your lungs?
• In the lungs, gas exchange takes place at the alveoli
• Alveoli

  • Their wall is only 1 cell thick, so the gas only needs to diffuse a short distance
  • All the little air sacs increase the surface area where gas exchange can take place
• Gas exchange occurs in the

  1. lungs

  2. alveoli
• The alveoli are tiny air sacs with some special adaptations that make them good for gas exchange
• Firstly, they increase the surface area where gas exchange can take place
• They are also only one cell thick, so the distance for oxygen to diffuse into the bloodstream is really short
• Air flow from the mouth/nose to the alveoli

  1. Nose

  2. mouth

  3. trachea

  4. bronchus

  5. bronchiole

  6. alveolus

  7. blood
• What is contained within the thorax?
• The trachea connects the mouth to the lungs, also known as the windpipe
• Oxygen molecule travels as it moves through the lungs

  Breathed in through the mouth, travels down the trachea, into the bronchi to the bronchioles and finally the alveoli
• Alveoli

  • Large surface area, moist, thin walls and a good blood supply
• Sebastian says "we breathe in oxygen and we breathe out carbon dioxide." Is Sebastian correct? Explain why or why not.
• Why can you see your breathe on a cold mirror?