The lungs develop from a structure called the respiratory diverticulum. This structure forms during the embryonic stage of human development, around the fourth week of gestation.

Here's a breakdown of how the lungs develop:

1. Respiratory diverticulum formation: The respiratory diverticulum, also known as the lung bud, emerges as an outpouching from the ventral wall of the foregut, which is the early stage of the digestive tract.

2. Branching morphogenesis: The lung bud undergoes extensive branching, forming the bronchial tree, the network of airways that deliver air to the lungs.

3. Alveolar development: The terminal bronchioles, the smallest branches of the bronchial tree, develop into alveoli, the tiny air sacs where gas exchange takes place.

4. Maturation: Throughout fetal development, the lungs continue to mature, with the alveoli increasing in number and complexity.

Important Note: The lungs are not fully developed at birth. They continue to mature and grow for several years after birth.

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