Breathing and Gas exchange

• A constant supply of oxygen is needed to respire to produce energy
• The waste products of respiration are carbon dioxide and water (vapour)
• Inspiration allows us to bring oxygen into the body and expiration allows us to remove waste (carbon dioxide and water vapour) from the body
• Breathing - when muscles change the size of the lungs, allowing us to inhale and exhale
• Ventilation - movement of air into and out of the lungs
• Gas exchange - where the oxygen diffuses into the blood and carbon dioxide diffuses out
• Structure of the Thorax ( 10 )

  • Trachea
  • Bronchus (plural Bronchi )
  • Alveoli
  • Bronchioles
  • Pleural Membranes
  • Rib
  • Diaphragm
  • Intercostal muscles
  • Pleural cavity filled with pleural fluid
  • nasal cavity
• Trachea


  Brings air from the outside into the lungs
• Cartilage in the trachea and bronchi


  Prevents the airways from collapsing but their C shape lets them be flexible
• Diaphragm 


  Involved in breathing . It also separates the lungs from the digestive organs
• Rib


  Protects the lungs
• Intercostal muscles

  Moves the ribs
• Alveoli


  Site of gaseous exchange
• Pleural membranes


  makes the lungs airtight
• Pleural cavity filled with pleural fluid


  Lubricates the chest so the pleural membranes don’t become stuck to the chest wall
• Capillaries are types of blood vessels that surround air sacs
• red blood cells become bright red when transporting a lot of oxygen
• red blood cells come from the pulmonary artery to the alveoli
• How are alveoli adapted for efficient gas exchange

  • There are many alveoli which therefore means a large surface area for gas exchange ( 60m^2 )
  • Only one cell thick allowing for a short pathway
  • Well ventilated and lots of blood capillaries to allow a good blood supply to maintain a steep concentration gradient
  • moist surfaces for gases to dissolve so they can diffuse quickly
• goblet cells make mucus
• Mucus traps bacteria and unwanted particles which prevents them from entering the lungs. Ciliated cells waft mucus and trapped particles up towards the mouth
• Inhalation

  • The rib cage moves up and out
  • the external intercostal muscles contract
  • The diaphragm contracts and moves down ( flattens )
  • The volume increases
  • the pressure decreases
  • as there is less pressure inside the lungs, air moves in via the trachea
• Exhalation

  • The rib cage moves down and in
  • the external intercostal muscles relax
  • The diaphragm relaxes and moves up ( dome )
  • The volume of the lungs and chest cavity decreases
  • the pressure increases
  • the increase in pressure forces the air out
• There are over 4000 chemicals in a single cigarette
• Smokers are 20 times more likely to die from lung cancers than non-smokers
• Nicotine

  • Stimulant that affects the central nervous system
  • nicotine causes people to become addicted to cigarettes
  • Raises heart rate and narrows blood vessels leading to high blood pressure
  • this can lead to heart disease
• Tar

  • Carcinogen which means it causes cancer
  • A quarter of smokers die from a cancer
  • Is deposited in the lungs and coats the surface of the cilia
  • This ends up paralysing them
  • this means smokers cough more to move the mucus
  • Smokers are also more likely to get bronchitis due to trapped bacteria
• Carbon Monoxide

  • Poisonous gas reduces the amount of oxygen that red blood cells carry around the body
  • reduces the amount of oxygen that red blood cells carry around the body
  • Combines with the the haemoglobin in red blood cells
  • this prevents oxygen from combining with the red blood cells
  • This prevents blood from carrying oxygen around your body properly and forces the heart to work harder than it should, leading to a faster heart rate
  • this can lead to heart disease
  • If pregnant women smoke, it can reduce the birth mass of the baby
• Carcinogen 


  Causes cancer
• How can people give up smoking

  Hypnosis, Nicotine patches , gum , spray
• Smoking is hard to give up as the nicotine is a stimulant and addictive
• 90 % of lung cancer is caused by smoking
• tar paralyses the cilia by coating their surfaces, making chest infections more likely
• Emphysema


  A disease where the alveoli break down or burst which reduces the surface area for gas exchange in the lungs. This means more oxygen is needed so smokers have to breathe faster