Pleural diseases and extra-pulmonary disease

• Anatomy of the pleura:

  • Consists of a serous membrane with a layer of simple squamous cells supported by connective tissue
  • Simple squamous epithelial layer is known as the mesothelium
  • Divided into two parts: Visceral pleura (covers the lungs) and Parietal pleura (covers the internal surface of the thoracic cavity)
  • Continuous with each other at the hilum of each lung
  • Potential space between the viscera and parietal pleura known as the pleural cavity
• Neurovascular supply:

  • Parietal Pleura:
  • Sensitive to pressure, pain, and temperature
  • Innervated by the phrenic and intercostal nerves
  • Blood supply from the intercostal arteries
  • Visceral Pleura:
  • Not sensitive to pain, temperature, or touch
  • Receives autonomic innervation from the pulmonary plexus
  • Blood supply via the bronchial arteries
• Pleural cavity:

  • Potential space between the parietal and visceral pleura
  • Contains a small volume of serous fluid with two major functions:
  • Lubrication of the pleurae surfaces for smooth sliding
  • Production of surface tension to ensure lung expansion with thorax expansion
• Terminology:

  • Pleurisy: Inflammation of the pleura
  • Pleural effusion: Buildup of fluid in the pleural space
  • Chylothorax: Lymphatic fluid leaks into the pleura
  • Pneumothorax: Excess air or gas in the pleural space
  • Mesothelioma: Presence of a tumor in the pleural space
• Pleurisy:

  • Inflammation of the pleural membranes surrounding the lungs and chest cavity
  • Clinically presents with pleuritic chest pain
  • Symptoms include sharp chest pain on affected side, dry cough, pyrexia, dyspnea
  • Treatment involves addressing underlying cause and analgesia
• Pleural effusion:

  • Collection of excess fluid in the pleural space
  • Secreted from parietal cells and absorbed by visceral pleural microcirculation
  • Role in reducing friction between pleural layers for smooth lung expansion
  • Categorized as transudative or exudative based on fluid analysis
• Chylothorax:

  • Manifests from damage or dysfunction of thoracic duct and lymphatics
  • Appearance of fluid is usually milky
  • Rich in lymphocytes, predominantly T cells
  • pH of fluid is 7.4-7.8
  • Management involves addressing underlying cause
• Pneumothorax:

  • Occurs when air is present in the pleural space, causing lung collapse
  • Can be spontaneous (primary or secondary) or traumatic
  • Complications include tension pneumothorax, a clinical emergency
  • Management includes needle decompression and chest drain placement
• Mesothelioma:

  • Malignant growth of mesothelial cells, commonly affecting the pleural layer
  • Strongly associated with asbestos exposure
  • Professions at risk include shipbuilding, insulation work, mining, and auto parts manufacturing
  • Management involves surgical and oncological treatment
• Other extrapulmonary diseases impacting respiratory function:

  • Skeletal deformities affecting the thoracic cage
  • Obesity
  • Neuromuscular disorders such as muscular dystrophy and phrenic neuropathies