Hargens A R, Millard R W, Pettersson K, Johansen K
Nature. 1987;329(6134):59-60. doi: 10.1038/329059a0.
Because it is so tall, the giraffe, Giraffa camelopardalis, provides an important animal model for investigating adaptive mechanisms to orthostatic (gravitational) pressure changes. Previous physiological studies of the giraffe have concentrated on arterial blood pressures in the heart and neck. Briefly, these investigations revealed that arterial pressure near the giraffe heart is about twice that in humans, to provide more normal blood pressure and perfusion to the brain. Another important question is that of how giraffes avoid pooling of blood and tissue fluid (oedema) in dependent tissues of their extremities. As monitored by radiotelemetry, the blood and tissue fluid pressures that govern transcapillary exchange vary greatly with exercise. These pressures, combined with a tight skin layer, move fluid upward against gravity. Other mechanisms that prevent oedema include precapillary vasoconstriction and low permeability of capillaries to plasma proteins.
长颈鹿（学名：Giraffa camelopardalis）体型高大，为研究机体对直立位（重力）压力变化的适应机制提供了重要的动物模型。以往对长颈鹿的生理学研究主要集中在心脏和颈部的动脉血压。简而言之，这些研究表明，长颈鹿心脏附近的动脉血压约为人类的两倍，以确保为大脑提供更接近正常的血压和灌注。另一个重要问题是，长颈鹿如何避免四肢下垂部位血液和组织液的淤积（水肿）。通过无线电遥测监测发现，控制毛细血管间液体交换的血液和组织液压力会随运动大幅变化。这些压力与紧绷的皮肤层共同作用，使液体克服重力向上流动。其他预防水肿的机制包括毛细血管前血管收缩以及毛细血管对血浆蛋白的低通透性。
