C2 - Functions of the respiratory system

• breathing or ‘pulmonary ventilation’ is the process of air being transported into and out of the lungs

• inspiration (active) • expiration (passive)

• external intercostal muscles contract, lifting the ribs upwards and outwards • partial pressure drop inside the lungs to below atmospheric pressure • air particles move from an area of high concentration to an area of low concentration • diaphragm contracts an is forced downwards

• internal intercostal muscles contract, drawing the ribs downwards and inwards • partial pressure increases inside the lungs to above atmospheric pressure • air particles move from an area of high concentration to an area of low concentration • diaphragm relaxes and moves upwards

• occurs at the alveoli and working muscles • through the process of diffusion (high to low) • alveoli and capillary walls create a respiratory membrane which has gas on one side and blood on the other • oxygen is transferred through simple diffusion from high within the alveoli to low in the red blood cells • oxygen diffuses through the alveolar walls, the capillary wall through the red blood cell membrane and attaches to the haemoglobin in the red blood cell

• having a very high surface area • having a million of alveoli in each lung • having a very good blood supply