Lung Development and Laryngotracheal Diverticulum

• The laryngotracheal diverticulum is a foregut outgrowth that becomes the larynx and trachea.
• The heart being pushed down the pericardioperitoneal canal causes the formation of the laryngotracheal diverticulum.
• The respiratory diverticulum initially connects to the foregut.
• The esophagotracheal ridge forms, leading to the division into the esophagus and trachea.
• Tracheoesophageal folds appear along the lateral sides.

Lung Development Stages

• Embryonic Stage: Primary lung buds form.
• Pseudoglandular Stage: Respiratory bronchioles form and the mesoderm becomes vascularized.
• Canalicular Stage: Blood vessels grow and interact with developing lung structures.
• Saccular Stage: Primitive alveoli form.
• Alveolar Maturation Stage: Alveoli mature for gas exchange, and this continues into childhood.
• Lungs are fully mature and functional 22-26 weeks post-fertilization.
• Capillary beds surround the mature alveoli, facilitating gas exchange.
• Oxygen from the alveolus is transferred to the blood in the capillaries, while carbon dioxide is transferred from the blood to the alveolus.

Pleura Formation

• The lung bud expands into the visceral pleura without breaking into the pleural cavity.

Diaphragm Development

• The diaphragm develops from the central tendon and somites.
• The phrenic nerve (C3, C4, and C5 spinal nerves) innervates the diaphragm.
• Improper diaphragm development can lead to diaphragmatic hernia.
• Diaphragmatic hernia causes abdominal organs to compress the lungs.

Esophageal Atresia and Tracheal-Esophageal Fistula

• Esophageal atresia refers to blind pockets between the esophagus and trachea.
• Tracheal-esophageal fistula refers to an abnormal connection between the trachea and esophagus.
• Polyhydramnios is associated with both esophageal atresia and tracheal-esophageal fistula.
• Polyhydramnios is the excessive accumulation of amniotic fluid.

Lung Maturation Issues in Preterm Infants

• Surfactant is a slippery substance in the lungs that prevents tissue from sticking together.
• Surfactant keeps the lungs hydrated, and its absence can lead to lung dysfunction.
• Missing the period of surfactant production increases the risk of the fetus being non-viable
• Technology has helped improve the viability of fetuses born prematurely.