Editing Extracellular fluid (section)

== Oxygenation ==
One of the main roles of extracellular fluid is to facilitate the exchange of molecular oxygen from blood to tissue cells and for carbon dioxide, CO<sub>2</sub>, produced in cell mitochondria, back to the blood. Since carbon dioxide is about 20 times more soluble in water than oxygen, it can relatively easily diffuse in the aqueous fluid between cells and blood.<ref>{{Cite journal|last1=Arthurs|first1=G.J.|last2=Sudhakar|first2=M|date=December 2005|title=Carbon dioxide transport|url=https://linkinghub.elsevier.com/retrieve/pii/S1743181617305292|journal=Continuing Education in Anaesthesia, Critical Care & Pain|language=en|volume=5|issue=6|pages=207–210|doi=10.1093/bjaceaccp/mki050|doi-access=free}}</ref>

However, hydrophobic molecular oxygen has very poor water solubility and prefers hydrophobic lipid crystalline structures.<ref>{{Cite journal|last1=Bačič|first1=G.|last2=Walczak|first2=T.|last3=Demsar|first3=F.|last4=Swartz|first4=H. M.|date=October 1988|title=Electron spin resonance imaging of tissues with lipid-rich areas|url=http://doi.wiley.com/10.1002/mrm.1910080211|journal=Magnetic Resonance in Medicine|language=en|volume=8|issue=2|pages=209–219|doi=10.1002/mrm.1910080211|pmid=2850439|s2cid=41810978|url-access=subscription}}</ref><ref>{{Cite journal|last1=Windrem|first1=David A.|last2=Plachy|first2=William Z.|date=August 1980|title=The diffusion-solubility of oxygen in lipid bilayers|url=https://linkinghub.elsevier.com/retrieve/pii/0005273680904691|journal=Biochimica et Biophysica Acta (BBA) - Biomembranes|language=en|volume=600|issue=3|pages=655–665|doi=10.1016/0005-2736(80)90469-1|pmid=6250601|url-access=subscription}}</ref> As a result of this, plasma lipoproteins can carry significantly more O<sub>2</sub> than in the surrounding aqueous medium.<ref>{{Cite journal|last1=Petyaev|first1=I. M.|last2=Vuylsteke|first2=A.|last3=Bethune|first3=D. W.|last4=Hunt|first4=J. V.|date=1998-01-01|title=Plasma Oxygen during Cardiopulmonary Bypass: A Comparison of Blood Oxygen Levels with Oxygen Present in Plasma Lipid|url=https://portlandpress.com/clinsci/article/94/1/35/76833/Plasma-Oxygen-during-Cardiopulmonary-Bypass-A|journal=Clinical Science|language=en|volume=94|issue=1|pages=35–41|doi=10.1042/cs0940035|pmid=9505864|issn=0143-5221|url-access=subscription}}</ref><ref>{{Cite journal|last=Jackson|first=M. J.|date=1998-01-01|title=Plasma Oxygen during Cardiopulmonary Bypass|url=http://dx.doi.org/10.1042/cs0940001|journal=Clinical Science|volume=94|issue=1|pages=1|doi=10.1042/cs0940001|pmid=9505858|issn=0143-5221|url-access=subscription}}</ref>

If [[hemoglobin]] in erythrocytes is the main transporter of oxygen in the [[blood]], plasma lipoproteins may be its only carrier in the ECF.

The oxygen-carrying capacity of lipoproteins, reduces in [[ageing]] and [[inflammation]]. This results in changes of ECF functions, reduction of [[Tissue (biology)|tissue]] O<sub>2</sub> supply and contributes to development of tissue [[Hypoxia (medical)|hypoxia]]. These changes in lipoproteins are caused by oxidative or inflammatory damage.<ref>{{Cite journal|last1=Petyaev|first1=Ivan M.|last2=Hunt|first2=James V.|date=April 1997|title=Micellar acceleration of oxygen-dependent reactions and its potential use in the study of human low density lipoprotein|url=https://linkinghub.elsevier.com/retrieve/pii/S0005276097000052|journal=Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism|language=en|volume=1345|issue=3|pages=293–305|doi=10.1016/S0005-2760(97)00005-2|pmid=9150249|url-access=subscription}}</ref>