Anatomy of the Lungs

Introduction

• Lungs: A pair of respiratory organs located in the thoracic cavity.
  • Right and left lungs are separated by the mediastinum.
  • Spongy texture, gray or brown in young individuals.
  • Right lung: ~700 grams, heavier than the left lung.
  • 10 bronchopulmonary segments in each lung.

Features of the Lungs

• Shape: Conical with an apex and base.
• Borders: Three - anterior, posterior, and inferior.
• Surfaces: Coastal (outer) and medial (inner).
  • Medial surface divided into vertebral and mediastinal parts.

Detailed Features

Apex

• Blunt, lies above the anterior end of the first rib.
• Extends ~2.5 cm above the medial third of the clavicle.

Base

• Semilunar, concave, rests on the diaphragm.
• Separates lungs from liver (right lobe) and stomach, spleen (left lobe).

Borders

• Anterior: Thin, shorter; left lung has a cardiac notch.
• Posterior: Thick, extends from 7th cervical to 10th thoracic spine.
• Inferior: Separates the base from other surfaces.

Coastal Surface

• Large, convex, contacts the coastal pleura and thoracic wall.

Medial Surface

• Divided into vertebral (posterior) and mediastinal (anterior) parts.
• Related to vertebral bodies, intervertebral discs, and nerves.

Fissures and Lobes

• Right Lung: 3 lobes (upper, middle, lower); separated by oblique and horizontal fissures.
• Left Lung: 2 lobes; separated by oblique fissure.

Surface Marking

• Oblique and horizontal fissures demarcated by specific anatomical points on the ribs and costal cartilage.

Root of the Lung

• Connects medial lung surface to mediastinum.
• Comprises bronchus, arteries, veins, nerves, lymphatics, and areolar tissue.

Arrangement of Structures in the Root

• Anterior to Posterior: Superior pulmonary vein, artery, bronchus.
• Superior to Inferior: Different arrangements on right and left sides.

Relations of the Root

• Anterior Relations: Phrenic nerve, pericardiophrenic vessels, pulmonary plexus.
• Posterior Relations: Vagus nerve, pulmonary plexus, descending thoracic aorta (left side).
• Superior/Inferior: Vena cava (right), aortic arch (left), pulmonary ligament.

Blood Supply and Venous Drainage

• Arterial Supply: Bronchial arteries supply bronchi and lung tissue.
  • Right: 1 artery from 3rd posterior intercostal.
  • Left: 2 arteries from descending thoracic aorta.
• Venous Drainage: Pulmonary veins and bronchial veins (azygos and hemiazygos systems).

Lymphatic Drainage

• Superficial vessels drain peripheral lung tissue.
• Deep lymphatics drain bronchial tree.

Nerve Supply

• Parasympathetic: Derived from vagus nerve.
• Sympathetic: Derived from 2nd to 5th sympathetic ganglia.

Bronchial Tree

• Trachea: Divides into two primary bronchi at 4th thoracic vertebra.
• Right Bronchus: Shorter, wider, more aligned with trachea.
• Left Bronchus: Longer, narrower, more oblique.
• Lobar and Segmental Bronchi: 3 right lobar, 2 left lobar; 10 segmental bronchi per lung.

Bronchopulmonary Segments

• Anatomical, functional, surgical lung sectors.
• Defined by segmental bronchi and arteries.
• Right Lung: Upper, middle, lower lobes with specific segments each.
• Left Lung: Upper and lower lobes, segments in upper divided further.

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