Exchange surfaces

• What does heterotrophic mean?

  Organisms that obtain their energy by consuming other organisms.
• What does autotrophic mean?

  Organisms acquire nutrients differently e.g green plants
• What are factors affecting exchange surfaces?

  • size
  • surface area to volume ratio
  • level of activity
• How does size affect exchanging substances?

  Small or single celled organisms have a very short diffusion pathway from the membrane to the cell cytoplasm.
• What is inspiration?

  air moves into lungs
• What is expiration?

  air forced out of lungs
• Describe the trachea?

  it has C shaped pieces of cartilage. Has smooth muscle, goblet cells, elastic fibres and ciliated epithelium .
• What are precautions that must be taken while using a spirometer?

  • The subject should be healthy and in particular free from asthma.
  • The soda lime should be fresh and functioning.
  • There should be no air leaks in the apparatus as this would give an inaccurate or invalid result's.
  • The mouthpiece should be sterlised preventing disease transfer.
  • The water chamber must not be overfilled (or water may enter the air tubes).
• Goblet cells secrete mucus. The mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli.
• Smooth muscle in the walls of the trachea, bronchi, bronchioles allows their diameter to be controlled.
• Rings of cartilage in the walls of the trachea and bronchi provide support. It’s strjng but flexible and stops the trachea and bronchi collapsing when you breathe in and the pressure drops.
• Elastic fibres in the walls of the trachea, bronchi, bronchioles and alveoli help the process of breathing out. On breathing in, the lungs inflate and the elastic fibres are stretched. Then the fibres recoil to help push the air out when exhaling.
• Explain why a person using the spirometer to measure the vital capacity should wear a nose clip?

  ensure all air breathed comes from chamber or to prevent escape of air
• State two other precautions that should be taken when using a spirometer to measure its vital capacity?

  disinfect mouthpiece

  ensure there’s enough oxygen

  asthmatics can’t do it
• Explain why volume of air in the spirometer drop slowly over the first minute?

  • oxygen is used in respiration
  • carbon dioxide is released in respiration
  • CO2 is absorbed by soda lime
• Line shows vital capacity
• What chemicals absorb carbon dioxide?

  soda lime and sodium hydroxide
• Outline the mechanism of inspiration?

  diaphragm contracts and moves down. Ribs move upwards and outwards. Volume of thorax Increased. Pressure inside thorax falls to below atmospheric pressure so air enters lungs
• What is the function of the smooth muscle in the wall of the bronchus?


  Smooth muscle contracts, restricting the lumen of the bronchus to prevent harmful gases from entering the lungs.
• Describe the process of inspiration during ventilation?

  The external intercoastal muscles contract and move the ribcage upwards and outwards. The diaphragm contracts and becomes flatter. The volume of the thorax increases and the pressure in the thorax decreases.
• Explain why it is important to change the pressure inside the thorax during expiration?

  The pressure in the thorax increases during expiration, above atmospheric pressure. This forces air out of the lungs as air moves from high pressure to low pressure.
• What is the gill cover of a fish called?

  Operculum
• What does the operculum do?

  Protects the gills
• What features do the gills have which make them a good gas exchange?

  Large SA provided by the lamealle and gill filaments, good blood supply as supplied by capillaries.
• What are lamellae comparable to in the small intestines?

  Villi
• Describe the exhalation in mammal?

  Rib cage moves downwards and inwards. External intercostal muscles relax as diaphragm relaxes.
• Explain inspiration?

  • Diaphragm contracts to move down and become flatter. This displaces the digestive organs underneath.
  • The external intercostal muscles contract to raise ribs.
  • The volume of the chest cavity is increased
  • the pressure in the chest cavity drops below atmospheric pressure.
  • Air moves into the lungs.
• Explain expiration?

  • Diaphragm relaxes and is pushed up by the displaced organs underneath.
  • The external intercostal muscle relaxes and the ribs fall: the internal intercoastal muscle can contract to help push air out more forcefully- only during exercise.
  • Volume of chest cavity is decreased
  • the pressure in the chest cavity is raised abobe atmospheric pressure.
  • Air moves out of lungs.
• Why are the four types of stem cells?

  Totipotent, pluripotent, multipotent and unipotent
• What is a totipotent stem cell?

  Can divide and differentiate into any type of cell
• What is a pluripotent stem cell?

  Can self-renew and differentiate into any type of cell except the cells that make up the placenta.
• What is a multipotent stem cell?

  Can only differentiate and divide into a limited number of cell types
• What is a unipotent stem cell?

  Can only differentiate into a single type of cell e.g. cardiomyoblasts can only differentiate into cardiomyocytes.
• What is inspiration?

  external intercostal muscles contract,

  rib cage moves up & out,

  diaphragm contracts,

  volume of the thorax is increased,

  atmospheric pressure is greater than pulmonary pressure and air is forced into the lungs.
• What is expiration?

  internal intercostal muscles contract

  ribs move down and inwards

  diaphragm relaxes

  volume of the thorax is decreased,

  pulmonary pressure is greater than atmospheric pressure

  air is forced out of the lungs
• What is residual volume?

  is the volume of air left in the lungs after a forced expiration
• What is tidal volume?

  is the volume of air moved in and out of the lungs with a normal breath.
• What explains the absence of a transport system?

  it has a large surface area to volume ratio
• What is vital capacity?

  is the maximum amount of air that can be moved by the lungs in one breath
• Explain why tissue fluid does not contain erythrocytes?

  Erythrocytes are too large so cannot change shape to fit between endothelium cells.