In an adult giraffe, the systolic blood pressure, the pressure when the heart contracts to pump blood through the body, is about 200 millimeters of mercury at the level of the heart, about twice that of an adult human being.
During exercise, the blood pressure at the level of the giraffe’s feet might be double what it is at heart level because of gravity.
At the head, it is comparable to the blood pressure of a human being.
Stroke and hardening of the arteries can occur in most mammal species, but is not a notable problem with giraffes.
The giraffe’s circulatory system has evolved with special adaptations for both high and low pressure.
For example, because the blood pressure in the lower part of the body is so high, the artery walls in the legs are very thick, much thicker than in the neck, to prevent edema, or leakage of fluid out of the vessels.
The skin and tissue under the skin on the limbs are also very tight to prevent leaks.
In the large veins of the neck, there are valves to restrict the flow of blood so that it does not flow backward and pool in the head when the giraffe puts its head down to drink or eat.
