trachea - alveoli

• Branches of the tracheal bronchial tree


  • Trachea
  • Main bronchi
  • Lower bronchi
  • Segmental bronchi
  • Tertiary bronchi
  • Bronchioles
  • Terminal bronchioles
  • Respiratory bronchioles
  • Alveoli
• Bronchi


  Made up mainly of hyaline cartilage, non-collapsible
• Bronchioles


  Made up of connective tissue and smooth muscle, collapsible
• Bronchoconstriction


  Caused by contraction of smooth muscle in bronchioles, narrows airways
• Bronchoconstriction


  Occurs in severe asthma attacks and COPD
• Terminal bronchioles


  No gas exchange, just conducting air
• Respiratory bronchioles


  Gas exchange takes place
• Alveoli


  • Surrounded by pulmonary capillaries for gas exchange
  • Lined with alveolar fluid and surfactant to decrease surface tension
• Layers of respiratory membrane


  • Alveolar fluid with surfactant
  • Alveolar epithelium
  • Basement membrane of alveolar epithelium
  • Capillary endothelium
  • Basement membrane of capillary endothelium
  • Interstitial space
• Thickness of respiratory membrane affects gas diffusion
• Fluid accumulation in interstitial space


  Impairs gas exchange across respiratory membrane
• Ventilation


  The process of air movement in and out of the lungs
• Factors that affect membrane


  • Thickness of the membrane
  • Permeability of the membrane
• Fluid accumulation in the interstitial space


  Occurs in severe pneumonia
• In cases of pulmonary edema, there is a tendency for fluid to accumulate in the interstitial space
• Fluid accumulation in the interstitial space


  Significantly affects the gas exchange and diffusion of oxygen and carbon dioxide through the respiratory membrane
• Remember the six layers of the respiratory membrane and the order through which oxygen and carbon dioxide pass
• Ventilation


  The process of the movement of air into and out of the lungs during breathing
• Phases of ventilation

  • Inspiration
  • Expiration
• Principal muscles for respiration


  • Diaphragm
  • External intercostals
• During normal quiet breathing, no muscles are used for expiration</b>
• Accessory muscles for inspiration


  • Sternocleidomastoid
  • Scalenes
  • Pectoralis minor
• Accessory muscles for inspiration are only used during labored breathing or in COPD patients
• Contraction of external intercostals and diaphragm

  Causes the thoracic cavity to expand during inspiration
• Expiration is a passive process due to the elastic recoil of the thoracic cage and lungs
• Muscles used for forceful expiration


  • Abdominal muscles
  • Internal intercostals
• Polio victims suffer from respiratory failure due to paralysis of the respiratory muscles
• Cyclic changes in thoracic cavity volume


  Result in cyclic movement of air into and out of the lungs
• Boyle's Law


  Pressure is inversely proportional to volume of a gas
• Increase in thoracic cavity volume during inspiration


  Decreases the intrapulmonary/alveolar pressure
• Decreased intrapulmonary/alveolar pressure during inspiration


  Causes air to move from higher atmospheric pressure to lower pressure inside the lungs
• Decrease in thoracic cavity volume during expiration


  Increases the intrapulmonary/alveolar pressure
• Increased intrapulmonary/alveolar pressure during expiration


  Causes air to move from higher pressure inside the lungs to lower atmospheric pressure
• diffusion of oxygen


  from alveolus to red blood cells
• diffusion of CO2


  from red blood cell to alveolus
• where does the diffusion of O2 and CO2 happens?

  across the respiratory membrane of the lungs
• 2 sides of respiratory membrane

  alveolus and capillary
• 3 layers of alveolus

  alveolar fluid

  alveolar epithelium

  basement membrane of alveolar epithelium
• 2 layers of capillary (respiratory membrane)

  capillary endothelium

  basement membrane of capillary endothelium
• 6th layer of respiratory membrane

  interstitial space