L10-12 respiratory system

• average respiratory rate 


  12 to 15 times a minute
• approximately 500ml of air per breath
• cellular respiration occurs within tissue and is 


  the breakdown of glucose to produce STP, requires oxygen and releases carbon dioxide
• structure of respiratory system


  labels

  A) upper

  B) lower

  
• right lung has 3 lobes
• left lung has 2 lobes
• branching of bronchial tree:


  trachea- main bronchi-lobular bronchi-segmental bonchi-bronchioles-terminal bronchioles
• function of nose in respiratory system:

  • smell
  • filtration of particles
  • air passage
  • humidify air
  • elimination of mucous
  • warming air
• function of pharynx in respiratory system:

  • food passage
  • air passage
  • elimination of mucous
  • warming air
• function of larynx in respiratory system:

  • vocalisation
  • food passage
• cilia move mucous, so are eliminating mucous from the lungs
• goblet cells produce mucin
• warming air is important because:


  keeps the tubes open to be able to breathe
• get bronchial spasm of cold air intake
• conducting zone


  transfer air into the lungs
• respiratory zone


  gas exchange between blood and air
• conducting zone includes:


  nasal cavity, pharynx, bronchi, bronchioles, terminal bronchioles
• respiratory zone includes:


  respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
• during normal quiet breathing, the diaphragm, internal and external intercostal are used
• during forceful breathing more muscles are used to force air into lungs
• air moves in response to changes or difference in pressure
• atmospheric pressure is 760 mmHg
• intrapleural pressure is always negative, to help the lungs to expand and stay inflated
• inhalation:

  1. diaphragm contract, external intercostal muscles contract
  2. chest cavity and lung volume expand
  3. alveolar pressure drops to 758 mmHg
  4. atmospheric pressure is now higher than the internal pressure
  5. air is drawn from high to low pressure
• exhalation:

  1. diaphragm and external intercostal muscles relax
  2. lungs spring back (recoil) and chest cavity contracts
  3. contraction increases alveolar pressure to 762 mmHg
  4. air flows out of lungs towards atmospheric pressure
• volume of gas varies inversely with pressure
• factors affecting efficiency of lungs:

  • compliance
  • surface tension
  • airway resistance
• compliance is how stretchy the lungs are
• surface tension


  surfactant reduces surface tension
• airway resistance, airflow calculated by


  (P alveoli- P atmosphere)/resistance
• resistance increases on exhalation as bronchiole diameter decreases
• chemoreceptors responding to levels of oxygen, carbon dioxide, pH
• what controls quiet breathing

  dorsal respiratory group
• what controls forceful breathing

  ventral respiratory group
• proprioceptors feed information from motor cortex related to level of effort involved in exercise (for respiratory control centre)
• anatomical dead space


  not all air reaches the alveoli, but ventilates the trachea (ie filling the conducting zone)
• tidal volume


  amount taken in and exhaled on normal breath
• inspiration reserve volume


  amount taken in in a deep breath
• expiratory reserve volume 


  amount exhaled in forced exhalation
• residual volume 


  air not exchange but stays in lungs to keep inflated