A Preliminary Study on the Functionality of the Carotid-Vertebral Anastomotic Artery in the Regulation of Blood Flow in the Giraffe (Giraffa camelopardalis) by Duplex Ultrasound Examination

Blood changed direction inside one giraffe when its head was lowered. The change happened in a short vessel connecting two larger arteries in the neck. Such a connection could matter when the head moves between browsing height and the ground, reversing gravity's contribution to blood travelling towards the brain.

Marna van der Walt, Willem Daffue and colleagues mapped the connection using scans and dissections of two adult giraffe specimens. They then used ultrasound to follow blood in one living male. After chemical restraint and partial reversal of the immobilising drug, the animal remained down while its head and neck were moved between raised and lowered positions.

With the head raised, blood travelled through the connection from the vertebral artery towards the carotid artery. With the head lowered, the direction reversed. This demonstrated a posture-related change in that animal, not the amount of blood diverted or proven protection against brain injury in freely drinking giraffes. The authors proposed that the connection could supplement brain supply when the head rises and divert blood when it falls. The result offers a concrete mechanism to investigate: blood can switch direction in a particular linking vessel as the giraffe's posture changes.