In addition to providing camouflage, the patches on the skin of the giraffe have a unique vascular structure that works to regulate body heat, reports a special topic paper in the September issue of Plastic and Reconstructive Surgery, the official medical journal of the American Society of Plastic Surgeons (ASPS).
The skin structure underlying the giraffe’s dark skin patches provide a “thermal window” enabling thermoregulation of body structure—“a very efficient arrangement for rapid diversion of heated blood,” according to the new research, led by G. Ian Taylor, AO, FRACS, of The University of Melbourne, Victoria, Australia. They believe their findings may have implications for understanding the thermoregulatory function of blood flow in human skin, with possible applications to plastic surgery.
The Anatomy of the Giraffe’s Skin Patches
Occasioned by a sad event—the euthanasia of a giraffe in the Melbourne Zoo due to spinal injury—the researchers performed an in-depth study of the vascular anatomy of the giraffe skin. The study used a previously described method involving lead oxide injection for detailed definition of blood vessels.
X-ray studies revealed “an extraordinary and unique anatomical pattern of blood supply” to the dark skin patches. All skin patches in the neck, and more than 90% in the face, were supplied by a single artery that entered near the center of the patch and sent long branches radiating out toward the edge.
These vascular territories, called angiosomes, had a dense network of blood vessels capable of adjusting blood flow within the patch. Neighboring angiosomes were connected by “choke” arteries that could either prevent or permit exchange of heated blood between patches.
Other connections provided alternative pathways for diversion of heated blood. These included including direct connections between angiosomes, providing “an ‘express route’ for moving hot blood in emergency scenarios”; and a unique set of shunts for moving blood from arteries to veins, located in the pale skin between patches.
‘Sprinkler Mechanism’ to Help Control Body Temperature
The findings suggest that the giraffe’s patches play an important role in thermoregulation. Covering most of the body area, the dark patches “attract considerable heat on a hot day.” Combined with other characteristics—including the increased density of sweat glands and the nerves accompanying the supplying arteries—the pigmented angiosomes “may represent a controlled ‘on-off’ thermoregulating ‘sprinkler’ mechanism” as “an extreme example of cutaneous adaptation,” Taylor and colleagues write.
Comparison to other animals with similar skin spots or patches, such as the jaguar or African wild dog, found no evidence of a similar thermoregulating mechanism. The authors note that these other animals target prey in sudden bursts and then seek shade. That’s in contrast to the giraffe, whose food supply is in sunny areas, and which is too large to easily find shade.
The “extreme anatomical adaptations” of the giraffe’s skin patches “clearly informs our understanding of human anatomy, physiology and pathology,” Taylor and coauthors write. They add: “These studies inform ongoing investigations into vascular control in humans, in turn creating more decisive and reproducible results for our patients.
