Document Detail

Model analogues in the study of cephalic circulation.
MedLine Citation:
PMID:  10840228     Owner:  NLM     Status:  MEDLINE    
Simple laboratory models are useful to demonstrate cardiovascular principles involving the effects of gravity on the distribution of blood flow to the heads of animals, especially tall ones like the giraffe. They show that negative pressures cannot occur in collapsible vessels of the head, unless they are protected from collapse by external structures such as the cranium and cervical vertebrae. Negative pressures in the cerebral-spinal fluid (CSF) can prevent cerebral circulation from collapsing, and the spinal veins of the venous plexus can return blood to the heart in essentially rigid vessels. However, cephalic vessels outside the cranium are collapsible, so require positive blood pressures to establish flow; CSF pressure and venous plexus flow are irrelevant in this regard. Pressures in collapsible vessels reflect pressures exerted by surrounding tissues, which may explain the observed pressure gradient in the giraffe jugular vein. Tissue pressure is distinct from interstitial fluid pressure which has little influence on pressure gradients across the walls of major vessels.
R S Seymour
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Comparative biochemistry and physiology. Part A, Molecular & integrative physiology     Volume:  125     ISSN:  1095-6433     ISO Abbreviation:  Comp. Biochem. Physiol., Part A Mol. Integr. Physiol.     Publication Date:  2000 Apr 
Date Detail:
Created Date:  2000-08-15     Completed Date:  2000-08-15     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9806096     Medline TA:  Comp Biochem Physiol A Mol Integr Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  517-24     Citation Subset:  IM    
Department of Environmental Biology, University of Adelaide, SA 5005, Adelaide, Australia.
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MeSH Terms
Artiodactyla / physiology*
Blood Circulation*
Blood Pressure
Models, Biological*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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