The postnatal development of the respiratory system of the opossum. I. Light and scanning electron microscopy

摘要: The postnatal development of the respiratory system in opossum has been traced, using 102 specimens divided into 11 groups according to snout-rump length. At birth, lung is markedly underdeveloped and represented by a pumitive branching airways that end number terminal chambers or sacs. airways, constituting conducting portion lung, are lined columnar epithelium devoid cilia goblet cells. air contain an extensive capillary bed surfaced squamous interspersed with scattered cuboidal By 3 cm stage, bands smooth muscle have differentiated relation bronchial present trachea bronchi. Air immediately adjecent established bronchi differentiate further become incorporated tree new develop at most distal extent up 15.5 stage. Numerous spaces epithelium, which represent first appearance arbor alveolaris, appear within cellular stroma 7 opossum. 20 (juvenile) mature alveoli, containing many vacuolated cells, thick collagenous lamina developed between pleura parenchyma.