Myths and facts about the cardiovascular system of the giraffe PhD

Myths and facts about the cardiovascular system of the
giraffe
By
Myths and facts about the cardiovascular
system of the giraffe
Kristine Hovkjær Østergaard
PhD lecture
Being the tallest living animals, giraffes are endowed with a mean arterial
pressure (MAP) twice as high as other mammals, including humans. The
high MAP ensures adequate cerebral perfusion. However, the pressure
distribution changes enormously between postures, and most significantly
when comparing head-high to head-low postures. Moreover the hydrostatic
pressure differences within the giraffe cardiovascular system are enormous.
by
Kristine Hovkjær Østergaard
In humans, a high mean arterial pressure is associated with numerous
health related problems. The high pressure of the giraffe cardiovascular
system undoubtedly causes serious challenges to both the heart and the
systemic vasculature. Mechanisms must have evolved to protect the giraffe
cardiovascular system from the adverse effects of a high MAP.
Friday June 21st 2013
The present thesis aims to unveil some of the protective mechanisms in the
cardiovascular system in the giraffe and to gain knowledge of the evolutionary
adaptations accompanying the highest known MAP of any mammals.
Three expeditions to South Africa were undertaken by the DaGiR team (Danish
Cardiovascular Giraffe Research programme) to execute both physiological
and morphological studies of the giraffe. The thesis has its main focus on
the morphology of the heart, the conduit arteries of the lower extremities,
the neck and abdominal large veins (jugular and inferior caval vein) and the
carotid artery. Using stereological methods, quantitative morphology of
hearts, arteries and veins were examined and analysed. The morphological
results were correlated with functional data.
The morphological data reveal that the left ventricle of the giraffe heart
possesses significant differences in quantitative terms from other mammals.
The systemic vasculature shows structural specialisations which we suggest
to have regulative function. In addition, the structure of arteries and veins
below heart level point to a system with a low compliance, which would be in
accordance with the high MAP and a low blood volume.
This thesis is based on Kristine Hovkjær Østergaard’s research work at:
Centre for Clinical Research
Vendsyssel Hospital, Clinical Institute
Aalborg University
Denmark
Stereology and Electron Microscopy Research Laboratory
Department of Clinical Medicine and
Zoofysiology
Department of Bioscience
Aarhus University
Denmark
Program for PhD Lecture on
To fulfill the requirements for the Ph.D. degree, Ms. Kristine Hovkjær
Østergaard has submitted the thesis: Myths and facts about the
cardiovascular system of the giraffe, to the Faculty of Medicine at
Aalborg University.
Friday June 21st 2013
by
The Faculty Council has appointed the following adjudication
committee to evaluate the thesis and the associated lecture:
Professor Jim Hicks
Department of Ecology and Evolutionary Biology
University of California, Irvine
United States
Professor Lisbeth Høier Olsen
Department of Veterinary Disease Biology
University of Copenhagen
Denmark
Chairman:
Professor Søren Risom Kristensen
Department of Health Science and Technology
Aalborg University
Denmark
Moderator:
Clinical associate professor Gitte Nielsen
Clinical Institute
Aalborg University
Denmark
The Ph.D. lecture is public and will take place on:
Friday June 21st 2013 at 13:00
Vendsyssel Hospital, Auditorium
Bispensgade 37
9800 Hjoerring
Kristine Hovkjær Østergaard
Myths and facts about the cardiovascular system of the giraffe
Chairman:
Moderator:
Professor Søren Risom Kristensen
Clinical associate professor Gitte Nielsen
13.00
Opening by the Moderator
13.05
PhD lecture by Kristine Hovkjær Østergaard
13.50
Break
14.00
Questions and comments from the Committee
Questions and comments from the audience at the Moderator’s discretion
16.00
(No later than)
Conclusion of the session by the Moderator
After the session a reception will be arranged