Pathophysiology of pulmonary system

External structures

• Provide the external borders for the lungs
• Borders composed of:
  • Sternum
    • Provides anatomical landmarks for auscultation
  • Rib cage
    • 12 ribs and adjacent intercostal musculature assist with movement of air
    • Provide anatomical landmarks for auscultation
  • Vertebral column
    • Provides posterior border
  • Shoulder girdle
    • Provides attachment for accessory muscles to support in movement of air

Internal structures:

• Upper airways

  • Entry point for air
  • Comprised of nose, mouth, pharynx, and larynx

• Lower airways

  • Continue the conduction of air where gas exchange occurs
  • Comprised of trachea, bronchioles, alveolar ducts, and alveolar sacs

• Internal supporting structures

  • Each lung is divided into lobes and further subdivided into bronchopulmonary segments.
    • The right lung has three lobes—upper, middle, and lower—and a total of 10 bronchopulmonary segments:
      • Upper lobe: 3 segments- apical, posterior, anterior
      • Middle lobe: 2 segments- lateral, medial
      • Lower lobe: 5 segments- superior, medial basal, anterior basal, lateral basal, posterior basal
  • The left lung has two lobes—upper and lower—and typically 8 bronchopulmonary segments:
    • Upper lobe: 4 segments -apical, posterior, anterior, and lingular superior/inferior
    • Lower lobe: 4 segments- superior, anteriomedial basal, lateral basal, and posterior basal

• Pleura

  • Parietal pleura located on the outer surface and provides barrier to thoracic cage, diaphragm, and mediastinal border
  • Visceral pleura located on the inner surface and provides barrier to lung

Muscles and mechanics of ventilation

Primary muscles of inspiration

• Diaphragm
  • When contracted, muscle is pulled downward- inhalation
    • Leads to protruded abdominal cavity
  • When relaxed, muscle is in dome shape- exhalation
    • Takes the natural shape of lower rib cage
• Intercostals
  • Aid in movement of rib cage
• Accessory muscles
  • Scalenes
  • Sternocleidomastoid
  • Trapezius
  • Serratus anterior
  • Pectoralis muscles

Primary muscles for exhalation

• Passive recoil of activated inspiratory muscles
• Accessory muscles that can be utilized during disease state or exercise
  • Quadratus lumborum
  • Abdominal muscles
  • Sections of intercostals

Mechanism of breathing

• Inspiration
  • Activation of muscles to provide sufficient pressure gradient to allow for air to enter the lungs
  • Causes the movement of bony thorax outward
• Exhalation
  • Passive recoil of the activated muscle to allow air to leave the lungs
  • Causes the movement of bony thorax inward

Pulmonary function test - ventilation