What is the respiratory diverticulum and when does it form?

The respiratory diverticulum is the initial endodermal outgrowth from the foregut that gives rise to the entire respiratory system. It appears as a laryngotracheal groove in the floor of the primitive pharynx during the 4th week of intrauterine life.

How does the trachea separate from the esophagus during development?

A structure called the tracheoesophageal septum grows to separate the developing respiratory tract from the esophagus. Defects in this septum formation can lead to conditions like tracheoesophageal fistula.

What are the main stages of lung maturation?

Lung maturation occurs in four sequential stages: Pseudoglandular Stage (5–16 weeks) where bronchioles form, Canalicular Stage (16–26 weeks) where respiratory bronchioles and ducts appear, Terminal Sac Stage (26 weeks–birth) where gas exchange becomes possible, and Alveolar Stage (8 months–8 years) where definitive alveoli develop.

What causes laryngeal atresia or stenosis?

These conditions result from failure of recanalization during laryngeal development. When the epithelial lining of the larynx doesn't properly hollow out, it can create obstructions like laryngeal webs or complete atresia.

What is Respiratory Distress Syndrome (RDS) and why does it affect premature infants?

Respiratory Distress Syndrome (also called Hyaline Membrane Disease) is caused by surfactant deficiency in premature lungs. Surfactant, produced by type II pneumocytes, is essential for reducing surface tension in alveoli and only becomes adequate in the later stages of lung development.

What tissues give rise to the different components of the respiratory system?

The respiratory system has dual embryonic origins: Endoderm gives rise to the epithelial lining and glands, while splanchnic mesoderm forms cartilage, muscle, and connective tissue. Specific structures like laryngeal cartilages come from pharyngeal arch mesenchyme.

What is lung hypoplasia and what commonly causes it?

Lung hypoplasia refers to underdeveloped lungs that haven't reached their normal size or complexity. It's often associated with congenital diaphragmatic hernia, where abdominal organs compress the developing lungs in the thoracic cavity.

Respiratory System Development – Lung Stages

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