Gas exchange in humans🧬

• Name the organs..

  Trachea, bronchus
• Explain the downward movement of the diaphragm that leads to air entering the lungs

  the diaphragm going downwards and flattening increases the thoracic volume and the air pressure decreases as the air enters the lungs
• Describe what happens to the diaphram between times p(in) and Q(out)


  the diaphragm flattens and the diaphragm muscle contracts
• Air moves between times p and a explain how the diaphragm causes this

  The diaphragm moves downwards and flattens so thoracic volume increases and decreases air pressure so the air moves down the pressure gradient from high to low
• Describe how oxygen in the air in the alveoli enters the blood in the capillaries

  By diffusion across the alveolar epithelium
• How does it show the person breathing in?

  Volume of air increases
• Describe what happens to the shape of the diaphragm between times a and b (breath in)

  The diaphragm flattens as the diaphragm muscle contreacts
• Describe how substances can cross a cell membrane(6)

  1.simple diffusion from a high to low concentration gradient

  2.small molecules pass through a phospholipid bilayer

  3.water moves across by osmosis from a high water potential to a low water potential down a concentration gradient

  4.facilitated diffusion which requires proteins

  5.active Transport from a low to high concentration against the concentration gradient
• Describe how the lungs are adapted for rapid gas exchange

  loads of alveoli which gives a large SA for fast diffusion

  Alveolar epithelium - one cell thick short diffusion pathway for fast diffusion

  Ventilation - maintains concentration gradient so Fast diffusion
• Movement of ribs when a person breathes 


  Ribs move upwards and outwards
• Passive means..

  Without energy
• Is breathing of crocs passive ?

  no because it requires energy for muscle contraction
• Explain how the movement of liver causes the air to enter the crocodiles lungs

  Liver is pulled back

  This increases thoracic volume which results in air entering

  Lower pressure in the lungs than the outside
• describe the difference in composition of gases in inhaled and exhaled air

  Inhaled

  • more oxygen
  • Less carbon dioxide
  • Less water vapour
  • oxygen enters blood by diffusion
  • Water vapour diffuses from moist surface
  • Exhaled
  • Less oxygen
  • More carbon dioxide
• Inspiration vs expiration

  Inspiration - less carbon dioxide

  Expiration - more carbon dioxide
• Describe the role of diffusion in creating a difference

  Carbon dioxide diffuses from a high concentration in the blood cappilary to a low concentration in the alveoli
• during inspiration

  Internal and external intercostal muscles contact

  Cause rib cage to move upwards and outwards

  Diaphragm flattens

  Thoracic volume increases so pressure decreases in the lungs than the outside
• During expiration

  Internal and external intercostal muscles relax
• Describe the pathway taken by an oxygen molecule from alveolus to the blood

  Oxygen moves across the alveolar epithelium and then the cappilary endothelium
• Explain how a feature of the alveolus helps for efficient gas exchange

  Alveolar epithelium one cell thick short diffusion pathway do faster diffusion
• Evaluate the politicians statements

  For: significantly higher concentrations of carbon monoxide compared to the no smoking with the window closed

  Any increase in carbon monoxide is dangerous as is lessens amount of oxygen carried

  Against : not a significant difference if the window is open

  No data on child breathing rate
• a large number of small alveoli is more efficient why?

  Large surface area with small alveoli so faster rate of diffusion
• Type of cells in layer b

  Epithelial cells
• Composition of air before a person starts to exhale

  More carbon dioxide

  Less oxygen
• What causes the difference in composition between air alveolus and trachea ?

  Gas exchange takes place in the alveoli not the trachea
• vessel to leave the blood and enter the heart

  Pulmonary artery
• Why may some of the blood may contain carbon dioxide when returning to the heart?

  Lung cells may respire which releases carbon dioxide
• explain the mechanism that causes forced expiration

  External and internal intercostal muscles contract

  Diaphragm relaxes

  Decrease in thoracic volume

  Air pushed down a concentration gradient