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

• Published in: Veterinary dermatology 2011-12, Vol.22 (6), p.475-481
• Main Authors: Ninomiya, Hiroyoshi, Akiyama, Emi, Simazaki, Kanae, Oguri, Atsuko, Jitsumoto, Momoko, Fukuyama, Takaaki
• Format: Article
• Language: English
• Subjects: Animals; Arteries - ultrastructure; Arteriovenous Anastomosis - ultrastructure; Body Temperature Regulation; Cold Temperature; Corrosion Casting - veterinary; Dogs - anatomy & histology; Dogs - physiology; Foot - blood supply; Foot - physiology; Male; Microscopy, Electron, Scanning - veterinary; Venules - ultrastructure
• ISSN: 0959-4493; 1365-3164
• DOI: 10.1111/j.1365-3164.2011.00976.x

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. Résumé Les chiens sont bien adaptés aux climats froids et ils peuvent rester, marcher et courir sur la glace pendant de longues périodes. Contrairement au tronc, muni d’une fourrure dense et épaisse, les pieds sont plus exposés au froid à cause de l’absence de fourrure isolante. Les extrémités ont un rapport surface/volume élevé et perdent ainsi de la chaleur très facilement. Nous offrons une preuve anatomique des structures de conservation de la chaleur liée à la vascularisation des coussinets plantaires. Des préparations vasculaires au méthylméthacrylate pour microscopie électronique, des injections à l’encre Indian et des préparations histologiques ont été réalisées sur une série de 16 membres de 4 chiens adultes. Les moulages vasculaires et les colorations à l’encre Indian, ont montré que de nombreuses veinules étaient organisées autour des artères irrigant la surface du coussinet et formaient une triade veine‐artère‐veine, le réseau veineux peri‐artériel étant intimement relié aux artères. En outre, de nombreuses anasto