A giraffe’s neck has only seven cervical vertebrae. Surprisingly, this is the same number of vertebral bones in most mammalian necks. The 1.8 meter (6 feet) climb from shoulder to head requires an unusually powerful heart muscle. Weighing in at 11 kilogram (25 pound) the massive heart relies on a series of one-way arterial valves to propel the blood uphill. This tallest of all living land mammals has extreme metabolic requisites that has led to the evolution of a lung capacity that can capture 55 liters (12 gallons) of air.