Lecture Notes: The Lower Respiratory Tract

Overview

• The lower respiratory tract begins after the larynx.
• The key structures include:
  • Trachea
  • Bronchi
  • Lungs

Structure and Function

Trachea

• Made of cartilage, connects to the larynx.
• Cartilage forms a C-shape, missing at the posterior portions.
• Ends at the carina, where it divides into:
  • Right main bronchus
  • Left main bronchus

Bronchi

• Right and left main bronchi branch into the lungs.
• Right bronchus has a different angle due to the heart's position.

Lungs

• Right Lung:
  • Divided into three lobes: Superior (upper), Middle, and Inferior (lower).
• Left Lung:
  • Divided into two lobes: Superior (upper) and Inferior (lower).
• Contains a structure called the 'hilum' where bronchi, arteries, and veins enter/exit.

Vascularization

Pulmonary Circulation

• Starts with the right ventricle pumping blood through pulmonary arteries.
• Blood gets oxygenated in the lungs and returns via pulmonary veins to the left atrium.

Arteries and Veins

• Pulmonary Arteries: Carry deoxygenated blood away from the heart.
• Pulmonary Veins: Return oxygenated blood to the heart.

Anatomical Relationships

Mediastinum

• The space between the lungs.
• Contains:
  • Esophagus
  • Trachea
  • Aortic Arch

Lung Anatomy

• Apex: Pointed area at the top of the lung.
• Base: Broader area at the bottom of the lung.
• Fissures:
  • Oblique Fissure: Diagonal separation in both lungs.
  • Horizontal Fissure: Separates the middle and upper lobe in the right lung.
• Lingula: Small tongue-like projection in the left lung.

Pulmonary and Systemic Circulation

• Pulmonary Circulation: Primarily deals with oxygenation of blood in lungs.
• Systemic Circulation: Involves oxygenated blood being distributed throughout the body.

Key Concept

• Arteries and veins are defined by direction relative to the heart, not oxygenation status:
  • Arteries carry blood away from the heart.
  • Veins carry blood towards the heart.