Abstract
The morphological development that accompanies increasing pulmonary blood flow and decreasing pulmonary vascular resistance with advancing gestational age has not been delineated. To study this point we developed a method of comparing pulmonary arterial vessels of the same generations in fetal lambs. Pulmonary arteries were perfused with glutaraldehyde solution at pressures appropriate for gestational age and then injected with an India ink-gelatin-Micropaque mixture. Using the dissecting microscope and serially prepared sections we studied successively smaller generations of arteries. We assessed the medial width/external diameter ratio in a total of 825 vessels from six fetal lambs of 85 to 140 days gestation. In fifth generation, or resistance vessels, this ratio remained constant over the gestational period studied (N = 529, Y = 0.16, slope = 0.0003). We measured the volume of 17-34 randomly selected sections from each of the six fetuses, counted the total number of fifth and sixth generation vessels in these sections, and calculated the total number of these vessels per right lung. This number increased from 0.10 X 10(6) to 4.08 X 10(6) with increasing gestational age. The number of vessels per unit volume increased from 7.2 X 10(3)/ml to 61.8 X 10(3)/ml or right lung over this gestational period. The results indicate that increased pulmonary blood flow and decreased pulmonary vascular resistance with advancing gestation are due to an increase in the total number of vessels and increased vasomotor reactivity is related to an increase in the total amount of smooth muscle while the thickness of muscle in individual vessels remains constant.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.