Respiratory bud

Respiratory bud is a structure that forms in the early stages of embryonic development and eventually gives rise to the respiratory system. It is also known as the lung bud or the pulmonary bud.

Development

The respiratory bud forms during the fourth week of embryonic development. It originates from the foregut, a portion of the primitive gut tube, and is induced by the surrounding mesenchyme. The respiratory bud then divides into two lateral buds, known as the primary bronchial buds. These buds will eventually form the bronchi and the rest of the respiratory tree.

Morphogenesis

The process of respiratory bud morphogenesis involves a complex interplay of various growth factors and transcription factors. Key molecules involved in this process include Sonic hedgehog (Shh), Fibroblast growth factor (FGF), and Bone morphogenetic protein (BMP).

Shh signaling from the respiratory bud epithelium to the surrounding mesenchyme helps to regulate lung growth and branching. FGF signaling is involved in the proliferation of epithelial cells and the formation of the bronchial tree. BMP signaling is important for the differentiation of various cell types within the developing lung.

Clinical significance

Abnormalities in respiratory bud development can lead to a variety of congenital disorders, including pulmonary hypoplasia (underdevelopment of the lungs), pulmonary agenesis (absence of one or both lungs), and tracheoesophageal fistula (an abnormal connection between the trachea and the esophagus).

See also

• Embryogenesis
• Respiratory system
• Foregut
• Mesenchyme
• Bronchi