PHSIO RESPIPRATORY

• Functions of the respiratory system

  • Gas Exchange
  • Breathing
  • Sound Production
  • Olfactory Assistance
  • Protection
• Divisions of the respiratory system

  • Upper Respiratory Tract
  • Lower Respiratory Tract
• Parts of the Lower Respiratory Tract

  • Trachea
  • Right primary bronchus
  • Superior lobe
  • Middle lobe
  • Inferior lobe
  • Diaphragm
  • Left primary
  • Alveoli
  • Bronchioles
• Pulmonary ventilation is the inhalation (inflow) and exhalation (outflow) of air
• Inhalation or Inspiration

  1. Air pressure inside the alveoli must become lower than the atmospheric pressure

  2. Achieved by increasing the size of the lungs to increase lung volume and decrease pressure in the lungs to below atmospheric pressure
• Mammals inhale by moving the diaphragm to lower the air pressure in the chest cavity and pull air into the lungs
• The human chest cavity is always at a lower pressure than the outside environment (usually 760mmHg at sea level)
• Exhalation or Expiration

  1. Pressure in the lungs must be greater than the pressure of the atmosphere

  2. Exhalation starts when the inspiratory muscles relax

  3. Diaphragm relaxes and moves superiorly

  4. External intercostals relax and ribs are depressed

  5. These movements decrease the thoracic cavity volume, increasing alveolar pressure

  6. Air flows from higher pressure in alveoli to lower pressure in atmosphere
• Respiratory control centers

  • Medullary respiratory center
  • Pontine respiratory group
• Medullary respiratory center

  Made up of dorsal respiratory group (DRG) and ventral respiratory group (VRG)
• Dorsal respiratory group (DRG)

  • Generates impulses in bursts to diaphragm and external intercostals to cause inhalation
  • Becomes inactive after 2 seconds, allowing passive recoil of lungs and thoracic wall for exhalation
• Ventral respiratory group (VRG)

  • Contains pre-Bötzinger complex that may generate respiratory rhythm
  • Activated during forceful breathing to send impulses to accessory muscles of inhalation
• Pontine respiratory group

  • Contains apneustic center that sends signals for long, deep breaths
  • Contains pneumotaxic center that sends signals to inhibit inspiration and control respiratory rate
• Cerebral cortex allows voluntary alteration of breathing pattern
• Factors affecting rate of airflow

  • Effort needed for breathing
  • Alveolar surface tension
  • Compliance of the lungs
  • Airway resistance
• Alveolar surface tension

  Surface tension tends to collapse alveoli, but is countered by surfactant that reduces surface tension
• DRG neurons send nerve impulses
• Nerve impulses from the DRG neurons resume breathing, whether the person wants it to or not
• Voluntary control of breathing

  Protective because it enables us to prevent water or irritating gases from entering the lungs
• It is impossible for small children to kill themselves by voluntarily holding their breath, even though many have tried in order to get their way
• If breath is held long enough to cause fainting, breathing resumes when consciousness is lost
• Nerve impulses from the hypothalamus and limbic system also stimulate the respiratory center, allowing emotional stimuli to alter breathing as, for example, in laughing and crying
• Factors affecting rate of airflow

  • Amount of effort needed for breathing
  • Alveolar surface tension
  • Compliance of the lungs
  • Airway resistance
• Alveolar surface tension

  Surface tension tends to collapse the alveoli, but this is countered by surfactant which reduces the surface tension of water, keeping the alveoli open so that we can breathe easily
• Lung compliance

  The extent to which the lungs will expand (change in volume of lungs) for each unit increase in the trans-pulmonary pressure (when enough time is allowed for the system to reach equilibrium)
• Airway resistance

  The resistance of the respiratory tract to airflow during inhalation and exhalation, calculated as the pressure difference between the mouth and alveoli of the lung, divided by airflow
• Lung volumes are measured by spirometry, which is the most common type of pulmonary function or breathing test
• Flow-oriented incentive spirometer

  A standard flow-oriented incentive spirometer consists of three chambers in a row, with each chamber containing a ball that has printed on the outside the least amount of flow needed to raise the ball
• Factors affecting lung volumes and capacity

  • Larger in males, taller individuals, and younger adults
  • Smaller in females, shorter individuals, and the elderly
• Tidal Volume (TV)

  The amount of air inspired during normal, relaxed breathing, about 500 mL
• Inspiratory reserve volume (IRV)

  The additional air that can be forcibly inhaled after the inspiration of a normal tidal volume, about 3100 mL in an average adult male and 1900 mL in an average adult female
• Expiratory reserve volume (ERV)

  The additional air that can be forcibly exhaled after the expiration of a normal tidal volume, 1200 mL in males and 700 mL in females
• Residual Volume (RV)

  The volume of air still remaining in the lungs after the expiratory reserve volume is exhaled, about 1200 mL in males and 1100 mL in females
• Inspiratory Capacity

  The sum of tidal volume and inspiratory reserve volume, 3600 mL in males and 2400 mL in females
• Functional Residual Capacity

  The sum of residual volume and expiratory reserve volume, 2400 mL in males and 1800 mL in females
• Vital Capacity

  The sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume, 4800 mL in males and 3100 mL in females
• Tidal Volume (TV)

  Normal, quiet breathing involves inspiration and expiration of TV, which is ~500 mL
• Inspiratory Reserve Volume (IRV)

  The additional volume of gas that can be inspired above TV on maximal inspiration, ~3,000 mL
• Expiratory Reserve Volume (ERV)

  The additional volume of gas that can be expired below TV on maximal expiration, ~1,200 mL
• Residual Volume (RV)

  The volume of gas that remains in lungs following maximal expiration, ~1,200 mL