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gentex

GENTEX is a whole organ model of the vascular network providing intraorgan flow heterogeneity and accounts for substrate transmembrane transport, binding, and metabolism in erythrocytes, plasma, endothelial cells, interstitial space, and cardiomyocytes.

Model number: 0084

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Description

  GENTEX is a GENeric Tissue EXchange model characterizing the flow and transformation of metabolites. 
  GENTEX is a whole organ model of the vascular network providing intraorgan flow heterogeneity and 
  accounts for substrate transmembrane transport, binding, and metabolism in erythrocytes, plasma, 
  endothelial cells, interstitial space, and cardiomyocytes. 

Detailed GENTEX documentation

Equations

  • Flow velocities inside the capillary:

  • In a large vessel, the blood flow can be partitioned between plasma (p) flow and red blood cell (rbc) flow. The flows are given by:

    Fp = Fblood*(1-hLV) and Frbc = Fblood*hLV

    and the corresponding volumes are given by:
    Vp = Vblood*(1-hLV) and Vrbc = Vblood*hLV,
    where hLV stands for the hematocrit in the large vessel.

    It is easily seen that the velocities of plasma and rbcs are the same in the large vessel. (Velocity=Flow*Length/Volume).

    It has been noted that hematocrit inside capillaries, hc, is different then the hematocrit inside the large vessel supplying them. Since the volumes of plasma and rbc in the capillaries depend on hc, the volumes are different in the capillaries than in the large vessel. Hence the ratio of velocities must be different.

    Using:
    Vpcap=Vblood*(1-hc) and Vrbccap=Vblood*hc,

    the ratio of velocities is given by:
    RatioVel=(Frbc*L/Vrbccap)/(Fp*L/Vpcap) = hLV*(1-hc)/( (1-hLV)*hc ).

    If the Ratio of velocities is known, the capillary plasma hematocrit is given by:
    hc = hLV/(hLV-RatioVel*HLV +RatioVel).

  • Permeant Equations:





  • Initial Conditions:
    , , , .

    Boundary Conditions:

    ,

    ,

    ,

    , .

  • Extracellular Equations:




  • Initial Conditions:




    Boundary Conditions:









  • Vascular Equations:










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* Note: This JSim model project will run ONLY with JSim version 1.6.94 and above.
** Note: This JSim model project may not run in a Microsoft Windows XP or Vista environment.

The sample solution plots the input function in black with the concentration outflow curves for the vascular, extracellular, and permeant tracers (red, green, and blue, respectively). In the right panel, the extraction is plotted along with an estimated PS for the permeant tracer which is approximately the sum of the transfer rate between the capillary and the isf regions and the permeabiity-surface product governing the flux of material between the capillary and endothelial cell, i.e.,

.

References

  Poulain CA, Finlayson BA, Bassingthwaighte JB.,Efficient numerical methods for nonlinear-facilitated 
  transport and exchange in a blood-tissue exchange unit, Ann Biomed Eng. 1997 May-Jun;25(3):547-64.

  Bassingthwaighte JB, Raymond GR, Ploger JD, Schwartz LM, and Bukowski TR. GENTEX, a general multiscale model 
  for in vivo tissue exchanges and intraorgan metabolism. Phil Trans Roy Soc : Mathematical, Physical and Engineering Sciences 2006.

Related Models

Key Terms

purine nucleoside metabolism, convection-diffusion-reaction model, GENTEX, transporter, red blood cell, axially distributed blood-tissue exchange processes, constrained parameter estimation, simultaneous optimization.

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Acknowledgements

Please cite www.physiome.org in any publication for which this software is used and send one reprint to the address given below:
The National Simulation Resource, Director J. B. Bassingthwaighte, Department of Bioengineering, University of Washington, Seattle WA 98195-5061.

[This page was last modified 02Nov16, 2:33 pm.]

Model development and archiving support at physiome.org provided by the following grants: NIH/NIBIB BE08407 Software Integration, JSim and SBW 6/1/09-5/31/13; NIH/NHLBI T15 HL88516-01 Modeling for Heart, Lung and Blood: From Cell to Organ, 4/1/07-3/31/11; NSF BES-0506477 Adaptive Multi-Scale Model Simulation, 8/15/05-7/31/08; NIH/NHLBI R01 HL073598 Core 3: 3D Imaging and Computer Modeling of the Respiratory Tract, 9/1/04-8/31/09; as well as prior support from NIH/NCRR P41 RR01243 Simulation Resource in Circulatory Mass Transport and Exchange, 12/1/1980-11/30/01 and NIH/NIBIB R01 EB001973 JSim: A Simulation Analysis Platform, 3/1/02-2/28/07.