Respiratory System at Rest

• Pulmomary ventilation is breathing air in and out of the lungs.
• Gas exchange consists of external respiration and internal respiration.
• External respiration is the exchange of 02 and C02 between the blood and lungs (alveoli).
• Internal respiration is the exchange of 02 and C02 between the blood and muscle cells.
• The two lungs lie in the thoracic cavity. The right lung has three lobes and the left lung has two lobes, to accomodate the heart. Each lung is further divided into lobules, which are completely seperate units.
• Lungs are made of very elastic tissue - not muscle, and the elastic tissue is important because it stretches and recoils during inspiration and expiration.
• The alveoli are minute air sacs. Each individual air sac is called an alveolus. This is the site of gas exchange. There are approximately 300 million alveoli in the lungs, providing a vast surface area similar to that of half a tennis court.
• The walls of the alveoli are extremely thin (single-cell layer of epithelial cells) and elastic and are surrounded by capillaries. They have the biggest capillary network of anywhere in the body, which provides a short diffusion path and moist lining of water helping to diffuse and exchange oxygen.
• Breathing frequency is the number of inspirations or expirations per minute.
• Tidal volume is the volume of air inspired or expired per breath.
• Minute ventilation is the volume of air inspired or expired per minute.
• Resting Values: Untrained

  Breathing Frequency: 15br/min

  Tidal Volume: 0.5l

  Minute Ventilation: 7.5l/min
• Resting Values: Trained

  Breathing Frequency: 12br/min

  Tidal Volume: 0.5l

  Minute Ventilation:6l/min
• Submaximal Values: Untrained

  Breathing Frequency: can plataeu due to O2 demand=O2 supply

  Tidal Volume: 3l

  Minute Ventilation: 70l/min
• Submaximal Values: Trained

  Breathing Frequency: can plateau due to O2 demand=O2 supply

  Tidal Volume: 3l

  Minute Ventilation: 70l/min
• Maximal Values: Untrained

  Breathing Frequency: 40br/min

  Tidal Volume: 2.5l

  Minute Ventilation: 100l/min
• Maximal Values: Trained

  Breathing Frequency: 60br/min

  Tidal Volume: 3.5l

  Minute Ventilation: 210l/min
• Inspiration at rest: external intercostals contract, ribs and sternum move up and out diaphragm contracts and flattens, thoracic cavity volume increases, lung air pressure decreases.
• Inspiration during exercise: external intercostals contract with more force, sternocleidomastoid and pectoralis minor contract, diaphragm contracts and flattens more ribs and sternum move up and out more, thoracic cavity volume increases more, lung air pressure decreases more.
• Expiration at rest: external intercostals relax, diaphragm relaxes and domes ribs and sternum move down and in, thoracic cavity volume decreases, lung air pressure increases.
• Expiration during exercise: internal intercostals contract, rectus abdominus contract, external intercostals relax, diaphragm relaxes and domes more, ribs and sternum move down and in more, thoracic cavity volume decreases more, lung air pressure increases more.