Hughes Stephen, Barry John, Russell Jeremy, Bell Robert, Gurung Som
Biomedical Engineering and Medical Physics, School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia
School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), 2 George Street, Brisbane, QLD 4000, Australia.
J Exp Biol. 2016 Apr 15;219(Pt 8):1154-61. doi: 10.1242/jeb.137448. Epub 2016 Mar 4.
How blood was able to reach the heads of the long-necked sauropod dinosaurs has long been a matter of debate and several hypotheses have been presented. For example, it has been proposed that sauropods had exceptionally large hearts, multiple 'normal' sized hearts spaced at regular intervals up the neck or held their necks horizontal, or that the siphon effect was in operation. By means of an experimental model, we demonstrate that the siphon principle is able to explain how blood was able to adequately perfuse the sauropod brain. The return venous circulation may have been protected from complete collapse by a structure akin to the vertebral venous plexus. We derive an equation relating neck height and mean arterial pressure, which indicates that with a mean arterial pressure similar to that of the giraffe, the maximum safe vertical distance between heart and head would have been about 12 m. A hypothesis is presented that the maximum neck length in the fossil record is due to the siphon height limit. The equation indicates that to migrate over high ground, sauropods would have had to either significantly increase their mean arterial pressure or keep their necks below a certain height dependent on altitude.
血液如何到达长颈蜥脚类恐龙的头部长期以来一直是个有争议的问题，并且已经提出了几种假说。例如，有人提出蜥脚类恐龙有异常大的心脏，或者在颈部有多个间隔规则的“正常”大小的心脏，或者它们将颈部保持水平，抑或是虹吸效应在起作用。通过一个实验模型，我们证明虹吸原理能够解释血液如何充分灌注蜥脚类恐龙的大脑。静脉回流循环可能受到类似于椎静脉丛的结构的保护，从而避免完全塌陷。我们推导了一个将颈部高度与平均动脉压相关联的方程，该方程表明，在平均动脉压与长颈鹿相似的情况下，心脏与头部之间的最大安全垂直距离约为12米。本文提出了一个假说，即化石记录中的最大颈部长度是由虹吸高度限制所致。该方程表明，为了在高地迁徙，蜥脚类恐龙要么必须显著提高其平均动脉压，要么根据海拔高度将颈部保持在一定高度以下。
