Embryological Development of the Lungs

Introduction

• Speaker: Mean-ass
• Topic: Embryological development of the lungs
• Objective: Simplify the understanding of lung development for all levels of knowledge in embryology.

Early Embryological Stages

• Blastula Stage:
  • Formed by the fusion of sperm and egg.
  • Implantation on the uterine wall.
  • Undergoes gastrulation, forming three germ layers:
    • Ectoderm (blue)
    • Mesoderm (red)
    • Endoderm (green)

Germ Layers and Their Roles

• Ectoderm: Forms the neural tube.
• Mesoderm: Divided into three parts:
  • Paraxial Mesoderm: Becomes muscle.
  • Intermediate Mesoderm: Develops into kidneys.
  • Lateral Plate Mesoderm:
    • Somatic Mesoderm
    • Splanchnic Mesoderm (related to lung development)
• Endoderm: Forms the epithelial cells of the lungs.

Lung Development

• Week 4:

  • Lungs emerge as an outgrowth from the ventral part of the foregut.
  • Respiratory Diverticulum: Outpouching from the GI tract.
  • Tracheoesophageal Ridges: Form and pinch off the respiratory diverticulum.

• Week 5:

  • Formation of bronchial buds.
  • Development of right and left main bronchus.

• Week 6 to 8:

  • Lungs grow into the pericardial-peritoneal canal.
  • Formation of secondary bronchi (three on the right, two on the left).
  • Lung growth fills the visceral and parietal pleura.

Histological Development

• Terminal Bronchioles: Last point without alveoli.
• Respiratory Bronchioles: Begin to form alveoli.
• Type 1 Alveolar Cells: Squamous epithelium for gas exchange.
• Type 2 Alveolar Cells: Produce surfactant.

Prenatal Lung Environment

• Lungs filled with fluid (phospholipids, proteins, surfactant).
• Fluid affects macrophages that initiate labor via prostaglandins.
• Fluid is mostly absorbed at birth; surfactant remains essential for breathing.

Potential Developmental Issues

• Esophageal Atresia:
  • Forms:
    • Blind end with fistula connecting to distal esophagus.
    • Two blind ends.
    • Communication with trachea but maintains a complete esophagus to the stomach.

Conclusion

• Key Points Recap:

  • Lung epithelial cells from endoderm.
  • Connective tissues, muscle, and cartilage from splanchnic mesoderm.
  • Importance of surfactant in lung function at birth.

• Thank you for your attention.