Lungs

• Inspiration 


  External IC muscles contract

  Rib cage goes up and out

  Diaphragm is contracted and flattens

  chest volume increases

  Chest pressure decreases
• Expiration 


  External IC muscles relax

  Ribcage goes down and in

  Diaphragm is relaxed and curved

  Chest volume decreases

  Chest pressure increases
• alveoli


  high concentration gradient- constant blood flow in capillary network and ventilating the lungs

  short diffusion distance- alveoli and capillary are 1 cell thick

  large SA- millions of alveoli

  moist-helps gases dissolve and diffuse across faster
• IB drawing 


  Alveoli

  
• pneumocytes type 1


  very long bit thin cell. this gives a very short diffusion distance. they are squamous. they also make up the majority of the alveoli's surface area
• pneumocytes type 2


  produce pulmonary surfactant
• pulmonary surfactant 


  reduces cohesive forces and surface tension in alveoli. it ensures alveoli inflate at a constant rate to avoid lungs collapsing
• emphysema 


  a lung condition whereby the walls of the alveoli lose there elasticity due to damage to the alveolar walls caused by smoking
• what is the mechanism by which elasticity and lung tissue is damaged?

  damage to lung tissue leads to the recruitment of phagocytes to the region which produces an enzyme called elastase. this is released as part of an inflammatory response and breaks down the elastic fibres in the alveoli
• treatments of emphysema

  bronchodilator- used to relax the bronchiolar muscle to improve airflow

  corticosteroids- reduce inflammatory response that will break down the elastic fibres

  elastase activity can be blocked by an enzyme inhibitor provided elastase concentration is not too high
• symptoms of emphysema


  chronic cough- trying to cough up dead tissue

  feeling tired

  shortness of breath
• Tidal volume 


  The amount of air which enters and leaves the lungs during a normal breath at rest
• expiratory reserves volume

  the amount of extra air exhaled during a forceful breath out
• vital capacity 


  the most amount of air you can exhale after the deepest breath you can in
• residual volume 


  amount of air left in the lungs following maximum exhalation to avoid lungs collapsing
• inspiratory reserve volume 


  the amount of extra air breathed in during a deep breath