Key result
Giraffes maintain a mean arterial pressure of ~200 mm Hg to preserve cerebral perfusion against gravity.
Why the study?
The cardiovascular physiology of giraffes, especially their adaptations to very high blood pressure, has fascinated physiologists but requires comprehensive discussion.
This review highlights the unique structural and functional cardiovascular adaptations in giraffes that allow them to manage extremely high arterial blood pressures.
Answers are grounded in this paper and cite their sources.
High giraffe MAP sustains cerebral perfusion; leaves open its utility as a comparative model for human orthostatic physiology.
Gravity affects the physiology of many animals, and the effect is, for good reason, most pronounced in tall species. The physiology-in particular, cardiovascular function-of giraffes has therefore captivated the interest of physiologists for centuries. Several studies document high mean arterial blood pressure of giraffes of about 200 mm Hg. This appears necessary to establish a cerebral perfusion pressure on the order of 100 mm Hg at the cranial end of the carotid arteries. Here, we discuss the unique characteristics of blood vessels, the heart, and the kidney of giraffes and how these functional and structural adaptations are related to very high blood pressure. We also discuss how the cerebral circulation of giraffes is established and what we know about how the blood flow and arterial and venous pressures in giraffes change when they stop to drink and subsequently lift their heads 5-6 m in one sweeping movement.
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Aalkjær et al. (2020) conducted a review in Cardiovascular physiology of giraffes. Giraffes possess unique cardiovascular adaptations, including a mean arterial blood pressure of ~200 mm Hg, to maintain cerebral perfusion pressure of ~100 mm Hg against gravity.
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