The Department of Biomedicine

BBB seminar: Christian Aalkjær

The remarkable cardiovascular system of giraffes

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Christian Aalkjær
Department of Biomedicine, Aarhus University and Department of Biomedical Sciences, University of Copenhagen, Denmark

Being the tallest animal on earth giraffes experience substantial cardiovascular challenges from gravity. It is well documented that the mean blood pressure of giraffes is about 200 mmHg. This is probably to ensure an arterial pressure at the level of the head of approximately 100 mmHg. This hemodynamic challenge is aggravated when the giraffe within 1 sec. lowers its head to the ground for drinking and perhaps even more so, when it lifts its head again (also within 1 sec.) after a drinking session is completed. A grown up giraffe bull is about 6 meters high and if no compensation was possible this would mean that the arterial pressure in the head would increase some 400 mmHg when the head is near the ground. How do giraffes deal with these challenges?

We have addressed 4 questions which we think are relevant, when we want to understand how the hemodynamics of giraffes function:

  1. How is leg edema prevented?
  2. How can the heart produce a pressure of 200 mmHg?
  3. How is the kidney protected against the 200 mmHg?
  4. How are cerebral catastrophes avoided?

We have instrumented giraffes for measurements of blood pressure, arterial and venous pressures and flows. We have used ultrasound and histology to evaluate cardiovascular structure and we have studied vascular function in arteries isolated from different parts of giraffes.

In the seminar, I will provide answers or at least partial answers to these questions based on the results obtained with the techniques briefly outlined.

Chairperson: Helge Wiig, Department of Biomedicine