Respiratory Examination – Relevant Anatomy and Physiology

1. Division of Airway:

  • Extrathoracic (Upper) airway: Nose to Upper trachea
  • Intrathoracic (Lower) airway: Lower trachea to Alveoli and lungs

Note: Vocal fold is also regarded as the demarcating line between upper and lower respiratory tract

2. Angle of Louis: Junction of body of sternum to manubrium (2nd costal cartilage anteriorly and T4/5 sternal angleposteriorly)

  • 2nd rib joins manubrium (Start counting ribs)
  • Bifurcation of trachea
  • Beginning and end of arch of aorta
  • Division of pulmonary trunk
  • Division of mediastinum into superior and inferior
  • Thoracic duct crosses from left to right

3. Bronchi and bronchioles: About 25 divisions of which last 16 are bronchioles (no cartilage, less goblet cells and less musculature)

4. Lungs and pleura:

a. Base

At Mid-clavicular line (Midpoint between tip of acromion and suprasternal notch)

  • Lungs: 6th rib
  • Pleura: 8th rib

At Mid-axillary line (Midpoint between anterior and posterior axillary line)

  • Lungs: 8th rib
  • Pleura: 10th rib

At Vertebral line (Vertical line over spinous process midline)

  • Lungs: 10th rib
  • Pleura: 12th rib

b. Apex: 1 inch above the clavicle in midclavicular line

c. Medial border: Touches parasternal line at Angle of Louis

  • Right lung: Passes vertically downwards to reach base
  • Left lung: Follows outer margin of heart to reach base

d. Interlobar fissures:

  • Oblique/Major fissure: 6th rib in MCL – 5th rib MAL – medial border of scapula with hyperabducted arm – T2 spine
  • Horizontal/Minor fissure (Only on right): Sternum at level of 4th costal cartilage – first line of oblique fissure

Anteriorly: Most upper lobe and whole middle lobe; Posteriorly: Most lower lobe

surface lungs

5. Ribs: 1-7 attach to sternum by cartilage; 8-10 attach to eachother by cartilage; 11-12 floating ribs

6. Topographical division of chest:

a. Anteriorly:

  • Supraclavicular region
  • Infraclavicular region
  • Mammary region: Upper border of 3rd rib to Upper border of 6th rib (sternum to anterior axillary fold)
  • Infra-mammary region: Upper margin of 6th rib to lower margin of thorax

b. Laterally: between axillary folds

  • Axillary region: Upto upper margin of 6th rib
  • Infra-axillary region: Upper margin of 6th rib to lower edge of thorax

c. Posteriorly:

  • Suprascapular: Above spine of scapula
  • Scapular: Body of scapula below spine
  • Infrascapular: Below angle of scapula (7th rib)
  • Interscapular: Between posterior edge of scapula

PHYSIOLOGY

respiratory muscles

a. Inspiration:

  • Primary muscle: Diaphragm (Phrenic nerve – C3,4,5), External intercostal
  • Accessory muscle: Scalene, Sternocleidomastoid, Alae nasi, Serratus anterior, Others
    • Lift and expand chest wall up creating more negative intrathoracic pressure and thus more air enters lung

b. Expiration:

  • Primarily: Elastic recoil
  • Secondarily: Internal intercostal, Anterior abdominal wall muscles

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