Lungs

• Sequence for breathing in:

  1. Inspiration (breathing in)
  2. external intercostal muscles contract
  3. diaphragm contracts & flattens
  4. lung volume increases
  5. pressure in lungs decreases
  6. air flows in
• Sequence for breathing out:

  1. expiration (breathing out)
  2. external intercostal muscles relax: sternum & ribs move down & in
  3. diaphragm relaxes
  4. volume of thorax decreases
  5. pressure in lungs increases
  6. air flows out
• Parts of the lungs:

  • trachea
  • bronchi
  • bronchioles
  • alveoli
  • ribs
  • intercostal muscles (internal & external)
  • diaphragm
• The trachea needs cartilage to prevent it from collapsing as air pressure increases
• Cilia cells line the bronchi to move pathogens out of the lungs
• goblet cells produce mucus
• collagen & elastic fibres allow passive exhalation as they move back to their original shape without muscle movement needed
• tidal volume is the volume of air that is inhaled or exhaled in a single breath
• inspiratory reserve volume is the amount of air that can be inspired after the normal tidal volume
• residual volume is the volume of air left in the lungs to prevent them collapsing
• pulmonary ventilation rate (dm^3min^-1) = tidal volume (dm^3) X breathing rate (min^-1)
• peak flow monitor tests for & monitors asthma
• forced expiratory volume is the volume of air that can be exhaled after a forced exhalation
• forced expiratory volume measures lung volume (tests for bacteria or a collapsed lung)
• VO2 max looks at the efficiency of respiration
• Features of alveoli:

  • thin, partially permeable, large SA
  • covered in capillaries
  • rbc flattened against capillary wall to reduce diffusion distance
  • constant movement of internal and external media
• inspiration is active
• expiration is passive
• the recoil of elastic tissue in alveoli is responsible for forcing air out in resting breathing
• forced expiration is an active movement and requires the contraction of intercostal muscles
• tuberculosis is caused by bacteria and leads to the death of lung tissue: less SA for gas exchange
• fibrosis is caused through infection or exposure to particulate substances
• fibrosis leads to scar tissue in the lungs which is thicker and less elastic meaning lung expansion is reduced and diffusion distance is increased
• asthma is the inflammation, irritation and narrowing of airways
• asthma attacks are often due to allergies or a production of mucus
• emphysema is the inflammation of the lungs, often due to smoking or air pollution
• emphysema causes the walls of the lungs to break down, reducing the SA
• Key phrase:

  stretch and recoil