abnormal lung development abnormal lung-associated mesenchyme development csmith abnormal pulmonary mesenchyme development 2011-05-20T04:11:17Z abnormal lung mesenchyme development abnormality in the formation of the lung tissue comprised of multiple cell types (including connective tissue, endothelial cells, lymphatics, smooth muscle cells surrounding airways and blood vessels, myofibroblasts involved in septum formation, and cartilage-forming cells in the trachea), with most cells thought to be derived from the splanchnic mesenchyme, and other cells (endothelial, smooth muscle) believed to invade the lung as it expands; lung mesenchyme is a critical determinant of the shape and size of the developing lung, the extent and patterning of epithelial branching, and the formation of the pulmonary vasculature and interstitial mesenchymal components of the adult lung MPheno.ontology MP:0011142