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Vet Dermatol. :逆流换热系统让家犬脚掌在雪地里不冻僵

2012/01/15 来源:生物探索
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研究人员发现奥秘在狗的脚掌上,脚掌上有逆流换热交换系统可以让它们避免冻僵,而且家犬也有这套保暖系统。这项研究发表在Veterinary Dermatology杂志上。

Vet Dermatol. :逆流换热系统让家犬脚掌在雪地里不冻僵

日本科学家解决了存在已久的兽医学谜题:狗是如何能站立和长时间走在雪地和冰上,而且不会有明显的不舒服,更不会冻僵脚掌。研究人员发现奥秘在狗的脚掌上,脚掌上有逆流换热交换系统可以让它们避免冻僵,而且家犬也有这套保暖系统。这项研究发表在Veterinary Dermatology杂志上。

东京山崎学园大学(Yamazaki Gakuen University)的研究人员好奇为什么狗狗的脚掌似乎不会感觉到寒冷,即使脚掌比身体部分隔热毛更少。狗的脚掌里脂肪含量高,这就比其他组织更不容易冻僵,但因为表面积/体积比较大,这也意味着它们热量散发的很容易。

当人们暴露在寒冷的温度下时,四肢发生血管收缩从而减少血流量和热量消耗,以确保血液流到身体的其他部分不至温度太低。

由Hiroyoshi Ninomiya博士带领这个研究小组,使用扫描电子显微镜来研究四只成年狗的脚掌,发现动脉血管为脚垫供血,而动脉又与许多呈网状结构小的静脉和小静脉紧密联系,而这一系统实质上就是一逆流换热系统。

当热血通过动脉传到脚掌的时候,热量就传到和动脉紧密连着的小静脉那儿了,因此确保了血液在回流到身体的其他部位前就已经变热了。

逆流换热系统防止身体变冷并确保脚掌的温度保持在适当的限度。而且这一系统在其他的动物身上也有,比如说南极企鹅是在脚上和翅膀上,而海豚的逆流换热系统是在鳍上。

已知北极狐除了其他适应寒冷的方式,脚掌上也有逆流换热系统。但是这样的换热系统在家犬身上之前从未被怀疑或证实过。这项研究结果表明狗最初是在寒冷气候中被驯化的,在这样的气候中,此类的系统就有了存活优势。

当然家犬也不全都能忍受同样程度的冰冷情况,这还得取决于它们的生存环境(比如说习惯在室内)和品种。通常建议为帮家犬冬天冻伤脚掌,就是确保它们的脚掌不会分裂或者任何方式的损伤,而且在带它们到雪地里走前先在它们的脚掌上喷点烹饪油。狗狗生冻疮很少见,但还是会发生。


Functional anatomy of the footpad vasculature of dogs: scanning electron microscopy of vascular corrosion casts

Hiroyoshi Ninomiya, Emi Akiyama, Kanae Simazaki, Atsuko Oguri, Momoko Jitsumoto, Takaaki Fukuyama

Dogs are well adapted to cold climates and they can stand, walk and run on snow and ice for long periods of time. In contrast to the body trunk, which has, dense fur, the paws are more exposed to the cold due to the lack of fur insulation. The extremities have a high surface area-to-volume ratio, so they lose heat very easily. We offer anatomical evidence for a heat-conserving structure associated with dog footpad vasculature. Methylmethacrylate vascular corrosion casts for scanning electron microscopy, Indian ink-injected whole-mount and histological specimens were each prepared, in a series of 16 limbs from four adult dogs. Vascular casts and Indian ink studies showed that abundant venules were arranged around the arteries supplying the pad surface and formed a vein–artery–vein triad, with the peri-arterial venous network intimately related to the arteries. In addition, numerous arteriovenous anastomoses and well-developed venous plexuses were found throughout the dermal vasculature. The triad forms a counter-current heat exchanger. When the footpad is exposed to a cold environment, the counter-current heat exchanger serves to prevent heat loss by recirculating heat back to the body core. Furthermore, the arteriovenous anastomoses shift blood flow, draining blood to the skin surface, and the venous plexuses retain warm blood in the pad surface. Hence, the appropriate temperature for the footpad can be maintained in cold environments.

文献链接:http://pubmed.cn/21438930

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