The Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom.
J Theor Biol. 2011 Dec 21;291:33-41. doi: 10.1016/j.jtbi.2011.09.008. Epub 2011 Sep 22.
Oxygen transport from maternal blood to fetal blood is a primary function of the placenta. Quantifying the effectiveness of this exchange remains key in identifying healthy placentas because of the great variability in capillary number, caliber and position within the villus-even in placentas deemed clinically "normal". By considering villous membrane to capillary membrane transport, stationary oxygen diffusion can be numerically solved in terminal villi represented by digital photomicrographs. We aim to provide a method to determine whether and if so to what extent diffusional screening may operate in placental villi. Segmented digital photomicrographs of terminal villi from the Pregnancy, Infection and Nutrition study in North Carolina 2002 are used as a geometric basis for solving the stationary diffusion equation. Constant maternal villous oxygen concentration and perfect fetal capillary membrane absorption are assumed. System efficiency is defined as the ratio of oxygen flux into a villus and the sum of the capillary areas contained within. Diffusion screening is quantified by comparing numerical and theoretical maximum oxygen fluxes. A strong link between various measures of villous oxygen transport efficiency and the number of capillaries within a villus is established. The strength of diffusional screening is also related to the number of capillaries within a villus. Our measures of diffusional efficiency are shown to decrease as a function of the number of capillaries per villus. This low efficiency, high capillary number relationship supports our hypothesis that diffusional screening is present in this system. Oxygen transport per capillary is reduced when multiple capillaries compete for diffusing oxygen. A complete picture of oxygen fluxes, capillary and villus areas is obtainable and presents an opportunity for future work.
母体血液向胎儿血液输送氧气是胎盘的主要功能。由于绒毛内毛细血管数量、口径和位置的巨大变异性，即使在被认为临床“正常”的胎盘中，量化这种交换的效率仍然是识别健康胎盘的关键。通过考虑绒毛膜到毛细血管膜的转运，可以通过数值方法解决用数字显微照片表示的终末绒毛中的静止氧扩散问题。我们旨在提供一种方法来确定扩散筛选是否存在，如果存在，其程度如何。北卡罗来纳州 2002 年妊娠、感染和营养研究的终末绒毛分段数字显微照片被用作解决静止扩散方程的几何基础。假设母体绒毛氧浓度恒定，胎儿毛细血管膜完全吸收。系统效率定义为进入绒毛的氧通量与包含的毛细血管面积之和的比值。通过比较数值和理论最大氧通量来量化扩散筛选。各种绒毛氧转运效率的测量值与绒毛内毛细血管数量之间存在很强的联系。扩散筛选的强度也与绒毛内的毛细血管数量有关。我们的扩散效率测量值随着每个绒毛的毛细血管数量的增加而降低。这种低效率、高毛细血管数量的关系支持了我们的假设，即扩散筛选存在于该系统中。当多个毛细血管竞争扩散氧气时，每个毛细血管的氧气输送量会减少。可以获得完整的氧气通量、毛细血管和绒毛面积图，并为未来的工作提供机会。
