The Idea of an Essay, Volume 2

124 fainting is one of the many problems that could inhibit a giraffe if it did not possess the unique and perfectly designed circulatory system that it does. The giraffe towers over all the other mammals on earth. An average adult male can reach a height of eighteen feet; ten feet from the hoof to the shoulder and an additional eight feet coming from the length of the neck alone (Pitman, 2011). Due to the giraffe’s extreme anatomical structure, its circulatory system must be uniquely designed. This essay explains the need for hypertension (high blood pressure) in the giraffe, the structure and size of the heart in the giraffe, and four unique mechanisms, located throughout the circulatory system, which prevent problems that occur as a result of hypertension. The giraffe (Giraffa Camelopardalis) is the tallest mammal on earth. Since the giraffe’s head ranges anywhere from eight to ten feet above its heart, its heart must pump extremely hard to supply the brain with the oxygen and nutrients it requires (Zhang, 2006). Therefore, compared to humans, giraffes have exceptionally high blood pressures (Zhang, 2006). The high blood pressure is referred to as hypertension. The average blood pressure is also commonly called arterial pressure. According to Ostergaard et al. (2011), giraffes have a mean arterial pressure (MAP) of 350 mmHg from the hoof to the brain and 250 mmHg from the heart to the brain. This is extremely high compared to the human MAP, which is roughly 100 mmHg. However, the “arterial pressure at the entrance to the skull is surprisingly similar to that of other mammals, including humans (approximately 100mmHg)” (Ostergaard et al., 2011, p. 691; Brondum, 2009; Hargens et al., 1987). The pressure of the blood entering into the brain is extremely low compared to the pressure it takes to send the blood from the hoof to the brain or from the heart to the brain. However, according to Zhang (2006), “The blood pressure would need to be higher than 205.6 mmHg for blood not only to reach the brain, but also to be able to perfuse the vascular bed and maintain normal function of the brain” (p. 64). Because of its remarkable height, the giraffe’s heart must be strong enough to pump the blood a great distance in order to reach the brain at the proper pressure and supply it with oxygen and nutrients. One may naturally assume that the giraffe’s heart must be disproportionally large in order to overcome the force of gravity and carry the blood to the brain. However, that is not the case. It