Anatomy 1

• Changes in thoracic wall movements during respiration are due to:

  • Type & angles of articulations
  • Movement of sternum
  • Elasticity of costal cartilages
• Changes are classified into:

  • Changes in vertical diameter (SUP - INF)
  • Changes in ANT - POST diameter (pump handle motion)
  • Changes in transverse / LAT - LAT diameter (Bucket handle motion)
• Changes in vertical diameter are mainly due to excursion in the diaphragm:

  • During inspiration, the diaphragm contracts, increasing the vertical diameter of the thorax
  • During expiration, the diaphragm relaxes, decreasing the vertical diameter
• Changes in A - P diameter are mainly due to motion at upper ribs:

  • Upper ribs elevation pushes the sternum anteriorly & superiorly, increasing the A - P diameter
• Changes in transverse (LAT - LAT) diameter are mainly due to motion at lower ribs:

  • Lower ribs elevate, increasing the transverse diameter
  • Motion is more in the lateral part of ribs due to angled shape & indirect attachment of ribs
• Bronchial tree components:

  • Tracheobronchial tree / lower respiratory pathway allows passage of air into the lungs for gas exchange
  • Components include trachea, bronchi, and bronchioles
• Trachea:

  • Starts at cricoid cartilage @ C6
  • Bifurcates into 2 primary bronchi
  • Relations include the esophagus (post), thyroid & thymus (ant), and neurovascular structures (lat)
• Trachea's essential function is maintained by:

  • 15-20 c-shaped cartilages
  • Smooth muscle (trachealis m) closing gaps at the back
  • High content of elastic fibers in submucosa for elastic recoil during respiration
  • Mucus traps particles and cilia beat upwards to clear debris
• Bronchi:

  • Bifurcate from the trachea into 2 primary bronchi
  • Right primary bronchus leads to 3 secondary bronchi, while the left leads to 2 secondary bronchi (lobar bronchi)
  • Each lobar bronchus further divides into segmental/tertiary bronchi to supply bronchopulmonary segments
• Bronchopulmonary segments:

  • 10 per lung, pyramidal in shape
  • Each segment has its own connective tissue continuous with visceral pleura
  • Segmental branch of pulmonary artery supplies each segment
• Lungs:

  • Located within the pleural cavity, separated by the mediastinum
  • Surrounded by 2 layers of pleura (visceral and parietal)
• Pleura:

  • Serous membrane with visceral pleura adhering to lung surface and parietal pleura covering internal thoracic cavity surfaces
  • Pleural space/cavity between layers contains pleural fluid and is important for negative pressure within the cavity
• Neurovascular supply of pleura:

  • Visceral pleura is not sensitive to pain, temperature, or touch, only stretch
  • Receives autonomic innervation from pulmonary plexus and blood supply from bronchial arteries
  • Parietal pleura is sensitive to pressure, pain, and temperature, with innervation from specific nerves based on region
• Pleural recesses:

  • Costodiaphragmatic recess between costal and diaphragmatic pleurae
  • Costomediastinal recess posterior to the sternum
  • Inferior part of the lung expands into the costodiaphragmatic recess
• Pleural reflection:

  • Location where pleura changes direction
  • Pleural layers touch at reflection lines, creating pleural recesses for fluid accumulation and lung expansion during deep inspiration
• Lungs are located on either side of the mediastinum, each in its own thoracic cavity
• Lungs are surrounded by visceral pleura
• Each lung has:

  • Apex
  • Base (diaphragmatic surface)
  • 3 borders: Anterior (overlying pericardium), Inferior (base & costal), Posterior (costal & mediastinal)
  • 2 surfaces: Costal, Mediastinal
• Right lung:

  • 2 fissures (oblique & horizontal)
  • 3 lobes (superior, middle & inferior)
  • Ep-arterial/superior lobar bronchus to supply superior lobe
  • Extra-pulmonary
  • Most superior in root
• Left lung:

  • 1 fissure (oblique); 2 lobes (superior & inferior)
  • Anterior border: Cardiac notch
  • @ lower end → lingula
• Hilum of the LEFT lung:

  • Impressions (medial): Heart, Aorta, Arch, Descending/thoracic aorta, Trachea, Oesophagus
  • Superior lobe: Left subclavian vessels
  • Behind 3rd-4th costal cartilages
  • In relation to: T5-T7
• Hilum of the RIGHT lung:

  • Impressions (medial): Heart, Inferior vena cava, Superior vena cava, Azygos vein, Arch, Trachea, Oesophagus
  • Superior lobe: Right subclavian vessels
  • Behind 3rd-4th costal cartilages
  • In relation to: T5-T7
• Lungs have a double blood supply:

  • Pulmonary circulation for function
  • Bronchial arteries to supply lung cells with oxygen
  • Bronchial veins drain into Azygos vein (R), Accessory hemi-azygous vein (L), Pulmonary veins or RA
• Innervation:

  • Pulmonary nerve plexus
  • Formed by branches from the sympathetic trunk (T1-5/6) for broncho-dilators and vaso-constrictors
  • Parasympathetic fibres from vagus nerve (CN X) for broncho-constrictors and vaso-dilators
• Lymphatic drainage:

  • 2 lymphatic plexuses: Superficial (subpleural) and Deep
  • Drain into bronchopulmonary lymph nodes @ hilum
  • Bronchopulmonary nodes drain into tracheobronchial/carinal lymph nodes
  • 3 groups: 2 x Superior tracheobronchial lymph nodes, 1 x inferior/subcarinal tracheobronchial lymph nodes
• Mechanics of respiration:

  Quiet inspiration:

  • Diaphragm contracts inferiorly
  • External intercostal muscles contract
  • Muscles involved: Diaphragm, External intercostal muscles
• Forced inspiration:

  • Anterior and middle scalene, Sternocleidomastoid, Serratus anterior, Pectoralis minor
  • Muscles involved: Scalene muscles, SCM, Serratus anterior, Pectoralis minor, Pectoralis major
• Quiet expiration:

  • Passive process
  • Internal & innermost intercostal muscles move ribs inferiorly
  • Muscles involved: Internal and innermost intercostal muscles
• Forced expiration:

  • Active process
  • Anterior abdominal wall, Quadratus lumborum, Latissimus dorsi
  • Muscles involved: Anterior abdominal muscles, Quadratus lumborum, Latissimus dorsi