Acute and Subacute Effects of Injury on the Canine Alveolar Septum: Methods (4)
Serial sections of approximately 800-A thickness were cut of several contiguous alveoli. Each specimen was serially sectioned to depths varying from 31 to 83 p.. At intervals of every tenth to 20th section (0.08 to 1.6 p.m), the complete circumference of each alveolar profile was photographed by successive overlapping exposures (approximately 20 to 30 per profile) at a magnification of x 2,160. A calibration grid was photographed with each section. The resulting negatives were contact-printed and then montaged to reproduce the whole alveolar profile in cross section. There were 30 to 57 such successive montaged profiles of alveolar groups reconstructed from each specimen. buy ortho tri-cyclen online
The serial sections of the montaged profiles of the alveolar walls were examined with special emphasis on identifying discontinuities in the alveolar septum. A septal “gap” was defined as a discontinuity of the alveolar septum in all of its connective tissue components. Two types of discontinuities were identified. In one, complete discontinuity of all the elements of the septum including the interstitial and epithelial layers was present, and the borders of the interrupted septum were covered with alveolar epithelium, usually type 1 cell cytoplasm. This kind of septal gap, usually bridged only by the alveolar surface lining layer, or surfactant layer, was recognized as an interalveolar pore of Kohn. The other type of septal discontinuity involved all of the interstitial layers of the alveolar septum, including the alveolar epithelial basement membranes.