Human Anatomy: Lungs and Pleural Cavity

Parietal and Visceral Pleura

• Parietal pleura lines the chest wall
• Visceral pleura surrounds the lung
• The pleural cavity is between the two layers and contains a thin film of fluid for easy mobility of the lung

Lungs

• Each lung is a half-cone shape, taking the shape of the thoracic cavity
• Apex is the pointed upper end, projecting into the root of the neck through the thoracic inlet
• Base is the deeply concave surface, especially in the right lung due to the bulge of the liver
• Right lung is shorter and wider than the left lung

Borders of the Lungs

• Anterior border is thin and sharp
• Posterior border is rounded and blunt
• Inferior border is sharp all around the base except medially

Surfaces of the Lungs

• Costal surface is the lateral convex surface, related to the thoracic wall
• Mediastinal surface is the medial concave surface, related to the mediastinum
• Diaphragmatic surface (base) is deeply concave, especially in the right lung due to the bulge of the liver

Bronchi

• Each bronchus enters the hilum of the corresponding lung and divides into several generations of branching like a tree
• Differences between right and left bronchi:
  • Right bronchus is wider and shorter (2.5 cm), dividing before entering the lung
  • Left bronchus is narrower and longer (4.5 cm), dividing after entering the lung
  • Right bronchus forms a 25-degree angle with the vertical, while the left bronchus forms a 45-degree angle

Mediastinum

• A thick, massive median septum between the two lungs, kept in its median position by the equal intra-thoracic pressure on either side
• Contents: heart, big vessels, trachea, oesophagus, thoracic duct, and some important nerves
• Subdivisions:
  • Superior mediastinum, behind the manubrium
  • Inferior mediastinum, further subdivided into:
    • Middle mediastinum, containing the heart
    • Anterior mediastinum, in front of the heart
    • Posterior mediastinum, behind the heart

Respiratory System

• Parts of the respiratory system:
  • Nasal passages
  • Pharynx
  • Larynx
  • Trachea
  • Bronchi
  • Lungs
• Objectives of the lecture:
  • List the different parts of the respiratory system
  • Define the parts of nasal passages and walls of nasal cavity
  • Identify length, extension, and parts of the pharynx
  • Define the larynx and identify its length, extension, and structure
  • Identify the length, extension, and structure of the trachea
  • Differentiate between the right and left bronchi and define the branching of bronchi
  • Define the mediastinum, its subdivisions, and their contents
  • Define the pleura and its layers
  • Define the shape, borders, surfaces, lobes, fissures, and bronchopulmonary segments of the lungs
  • Differentiate between the right and left lungs