lungs

• the gas exchange in humans is about the inhaling of oxygen and the exhaling of carbon dioxide
• aerobic respiration is a chemical reaction
• respiration occurs in organelles called mitochondria
• the gas exchange system:

  air is inhaled through the mouth

  air enters the trachea

  the trachea splits into two bronchi

  the left bronchus goes into the left lung and the right broncus goes into the right lung

  in each lung the broncus splits in up to 30000 broncioles

  alvioli are at the tips of bronchioles
• alveoli:

  alveoli are air sacks in the lungs

  alveoli are where gas exchange takes place

  oxygen enters the blood from the alveoli

  oxygen travels to the heart from alveoli

  the heart pumps blood with oxygen in it around the body

  carbon dioxide leaves the blood through the alveoli
• alveoli walls:

  to maximise gas exchange alveoli have very thin walls

  alveoli walls are only one cell thick

  the thin alveoli walls allow more efficient diffusion of oxygen and carbon dioxide

  alveoli walls are moist and permeable

  gases can dissolve and pass through the alveoli
• the diaphragm:

  the diaphragm is an important muscle for breathing

  when you inhale it contracts

  the contracted diaphragm creates more volume within the ribcage

  the increased volume allows more air into the lungs