The Rostral Epidural Rete Mirabile: Functional Significance in Blood Flow Regulatory Mechanisms in Giraffe (Giraffa camelopardalis)

A giraffe's blood takes a winding route just before reaching its brain. Beneath the brain lies a meshwork of small arteries, rather than a single straight delivery pipe. That arrangement raises an intriguing possibility: the route itself could help moderate blood flow as the animal lowers and raises its long neck.

Marna van der Walt and colleagues studied heads from five giraffes obtained after management culls in South Africa. They used coloured latex to trace vessels, examined thin tissue sections and measured skull casts. They also pumped water through coiled aquarium tubing of different lengths to explore how a longer, winding passage changed flow and pressure.

The dissections located the arterial meshwork below the brain, and microscopy revealed muscle in its vessel walls. Longer tubing reduced water flow in the physical model. However, a single coiled tube does not reproduce the living network's many parallel branches, and the experiment did not measure protection in a drinking giraffe. The authors proposed that this network could help buffer incoming blood and maintain supply during head movements. The anatomical discovery is firmer than that functional explanation: the final journey to a giraffe's brain is through an intricate network whose role must be tested at that scale.