BIO 115 Lecture Notes - Lecture 7: Alveolar Cells, Lateral Plate Mesoderm, Pulmonary Pleurae
Document Summary
How the lungs develop from the laryngotracheal diverticulum (lung bud) and how the epithelium matures. Identify the time that the lungs are functional in a premature birth. The larynx, trachea and lungs develop from the laryngotracheal (lung bud) diverticulum of splanchnopleure that grows ventrally off the foregut. The endoderm gives rise to respiratory epithelium. The splanchnic mesoderm gives rise to all other components and cells of the airway (cartilage, smooth muscle, connective tissue, visceral pleura). Left and right lung buds grow into the pleural cavities that are partitioned segments of the intraembryonic coelom. Embryonic period (0-6 weeks): branching of the bronchi. The epithelium is an undifferentiated simple cuboidal epithelium. Pseudoglandular period (6 to 16 weeks; the airway resembles an exocrine gland). Branching to the level of terminal bronchioles, but no air exchange segments. Blood vessels elaborate, but are not closely applied to the airway. Canalicular stage (16-26 weeks): branching down to primordial alveolar ducts surrounded by a rich vascular network.
