Parametric Studies on the Three-Layer Microcirculatory Model for Surface Tissue Energy Exchange

1986 ◽  
Vol 108 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Z. Dagan ◽  
S. Weinbaum ◽  
L. M. Jiji
Keyword(s):  
Venous Blood ◽  
Thermal Characteristics ◽  
Tissue Temperature ◽  
Capillary Perfusion ◽  
Metabolic Heat ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Parametric Studies ◽  
Counter Current ◽  
Cutaneous Blood

The new three-layer microvascular mathematical model for surface tissue heat transfer developed in [1, 2], which is based on detailed vascular casts and tissue temperature measurements in the rabbit thigh, is used to investigate the thermal characteristics of surface tissue under a wide variety of physiological conditions. Studies are carried out to examine the effects of vascular configuration, arterial blood supply rate, distribution of capillary perfusion, cutaneous blood circulation and metabolic heat production on the average tissue temperature profile, the local arterial-venous blood temperature difference in the thermally significant counter-current vessels, and surface heat flux.

Thermal Modeling of the Normal Woman’s Breast

1984 ◽  
Vol 106 (2) ◽  
pp. 123-130 ◽  
Author(s):  
M. M. Osman ◽  
E. M. Afify
Keyword(s):  
Venous Blood ◽  
Tissue Perfusion ◽  
3 Dimensional ◽  
Metabolic Heat ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Dimensional Finite Element ◽  
Element Technique ◽  
Arterial Blood Temperature ◽  
Good Agreement

A comprehensive thermal model of the normal woman’s breast is presented. The model is developed taking into consideration metabolic heat production, tissue perfusion with capillary blood, arterial and venous blood thermal interaction and change of arterial blood temperature with position. A series of computer programs are written using a 3-dimensional finite-element technique to evaluate the surface temperature distribution of the breast. Comparison between the results obtained for the model and those from thermograms of a woman’s breast are in good agreement.

scholarly journals Topsy-turvy: turning the counter-current heat exchange of leatherback turtles upside down

2015 ◽  
Vol 11 (10) ◽  
pp. 20150592 ◽  
Author(s):  
John Davenport ◽  
T. Todd Jones ◽  
Thierry M. Work ◽  
George H. Balazs
Keyword(s):  
Heat Exchangers ◽  
Venous Blood ◽  
Vascular Supply ◽  
The Body ◽  
Leatherback Turtles ◽  
The Core ◽  
Arterial Blood ◽  
Hip Muscles ◽  
Counter Current ◽  
Current Heat

Counter-current heat exchangers associated with appendages of endotherms feature bundles of closely applied arteriovenous vessels. The accepted paradigm is that heat from warm arterial blood travelling into the appendage crosses into cool venous blood returning to the body. High core temperature is maintained, but the appendage functions at low temperature. Leatherback turtles have elevated core temperatures in cold seawater and arteriovenous plexuses at the roots of all four limbs. We demonstrate that plexuses of the hindlimbs are situated wholly within the hip musculature, and that, at the distal ends of the plexuses, most blood vessels supply or drain the hip muscles, with little distal vascular supply to, or drainage from the limb blades. Venous blood entering a plexus will therefore be drained from active locomotory muscles that are overlaid by thick blubber when the adults are foraging in cold temperate waters. Plexuses maintain high limb muscle temperature and avoid excessive loss of heat to the core, the reverse of the accepted paradigm. Plexuses protect the core from overheating generated by muscular thermogenesis during nesting.

Cold-induced shivering in men with thermoneutral skin temperatures

1976 ◽  
Vol 41 (2) ◽  
pp. 142-145 ◽  
Author(s):  
A. G. Buguet ◽  
S. D. Livingstone ◽  
L. D. Reed ◽  
R. E. Limmer
Keyword(s):  
Venous Blood ◽  
Electromyographic Activity ◽  
Jugular Veins ◽  
Arterial Blood ◽  
Air Temperatures ◽  
Cold Room ◽  
Warm Blood ◽  
The Common ◽  
Counter Current ◽  
Skin Temperatures

Twenty-two male Caucasians, aged 20–47 yr, were exposed in a cold room to air temperatures of -33 degrees C while lying in sleeping bags for 2 h. Skin and rectal temperatures as well as electromyographic activity of the chin, forearm, and thigh, were recorded. Shivering occurred in all the subjects, even though skin temperatures were maintained between 31 and 33 degrees C. It is suggested that a counter-current heat exchange occurs whereby the warm blood of the common carotid artery is cooled by cool venous blood in the jugular veins. This cooled arterial blood, in irrigating the hypothalamus, causes shivering.

In vivo thermal conductivity of the human forearm tissues

1991 ◽  
Vol 70 (6) ◽  
pp. 2682-2690 ◽  
Author(s):  
M. B. Ducharme ◽  
P. Tikuisis
Keyword(s):  
Longitudinal Axis ◽  
Skin Surface ◽  
Tissue Temperature ◽  
Bioheat Equation ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Computed Tomography Scanning ◽  
Human Forearm

The effective thermal conductivities of the skin + subcutaneous (keff skin + fat) and muscle (keff muscle) tissues of the human forearm at thermal steady state during immersion in water at temperatures (Tw) ranging from 15 to 36 degrees C were determined. Tissue temperature (Tt) was continuously monitored by a calibrated multicouple probe during a 3-h immersion of the resting forearm. Tt was measured every 5 mm from the longitudinal axis of the forearm (determined from computed-tomography scanning) to the skin surface. Skin temperature (Tsk), heat loss (Hsk), and blood flow (Q) of the forearm, as well as rectal temperature (Tre) and arterial blood temperature at the brachial artery (Tbla), were measured during the experiments. When the keff values were calculated from the finite-element (FE) solution of the bioheat equation, keff skin + fat ranged from 0.28 +/- 0.03 to 0.73 +/- 0.14 W.degrees C-1.m-1 and keff muscle varied between 0.56 +/- 0.05 and 1.91 +/- 0.19 W.degrees C-1.m-1 from 15 to 36 degrees C. The values of keff skin + fat and keff muscle, calculated from the FE solution for Tw less than or equal to 30 degrees C, were not different from the average in vitro values obtained from the literature. The keff values of the forearm tissues were linearly related (r = 0.80, P less than 0.001) to Q for Tw greater than or equal to 30 degrees C. It was found that the muscle tissue could account for 92 +/- 1% of the total forearm insulation during immersion in water between 15 and 36 degrees C.

Capillary red blood cell flow and activation of white blood cells in chronic muscle ischemia in the rat

1997 ◽  
Vol 272 (6) ◽  
pp. H2757-H2764 ◽  
Author(s):  
S. I. Anderson ◽  
O. Hudlicka ◽  
M. D. Brown
Keyword(s):  
Blood Cell ◽  
Blood Cells ◽  
Time Course ◽  
Venous Blood ◽  
White Blood Cells ◽  
Muscular Activity ◽  
Capillary Perfusion ◽  
Arterial Blood ◽  
The Common ◽  
Increased Activity

Increased activity of ischemic skeletal muscles in which functional hyperemia is impaired has been linked with capillary endothelial swelling postcapillary white blood cell (WBC) adherence. The perfusion pattern of capillaries under these conditions and time course of WBC activation is not known. Capillary microcirculation was studied by videomicroscopy at rest and after muscle contractions (1 Hz, 10 min) in extensor digi-torum longus muscles of pentobarbital sodium-anesthetized rat during the early stages of chronic ischemia (unilateral ligation of the common iliac artery for 3 days) and in ischemic muscles subjected to increased activity (7 days of ischemia or 3 days of ischemia plus indirect electrical stimulation via planted electrodes, 10 Hz, 7 x 10 min on-90 min off/day) to investigate how perfusion was affected. All ischemic muscles had more intermittently flowing capillaries than did unoperated control) muscles. Temporal heterogeneity of perfusion at rest, assessed by velocity, time spent stationary, and stop/start frequency of red blood cells, was similar to control values in ischemic muscles but greater in ischemic muscles subjected to additional activity. Hyperemic responses to contractions were severely blunted in all ischemic groups. The portion of morphologically nonspherical WBCs, taken to indicate activation, was 24 +/- 3% in venous blood after 3 days of ischemia vs. 14 +/- 1% in control muscles and increased further by 7 days (42 +/- 2%) when activated cells were also found in arterial blood. Thus increased muscular activity may exacerbate the adverse effects of ischemia on capillary perfusion, and WBC activation, evident before endothelial swelling is apparent, provides the potential as a circulating signal for capillary swelling in the ischemic and other muscles.

Dissipation of metabolic heat in the horse during exercise

1993 ◽  
Vol 74 (3) ◽  
pp. 1161-1170 ◽  
Author(s):  
D. R. Hodgson ◽  
L. J. McCutcheon ◽  
S. K. Byrd ◽  
W. S. Brown ◽  
W. M. Bayly ◽  
...  
Keyword(s):  
Heat Loss ◽  
Carotid Arteries ◽  
O2 Uptake ◽  
Metabolic Heat ◽  
Blood Temperature ◽  
Arterial Blood ◽  
Respiratory Heat Loss ◽  
Common Peak ◽  
Response To Exercise ◽  
Kinetics Of

Horses were exercised at 40, 65, and 90% of their maximum O2 uptake (VO2max) until moderately fatigued (approximately 38, 15, and 9 min, respectively) to assess heat loss through different routes. Approximately 4,232, 3,195, and 2,333 kcal of heat were generated in response to exercise at these intensities. Of this, approximately 7, 16, and 20% remained as stored heat 30 min postexercise. Respiratory heat loss, estimated from the temperature difference between blood in the pulmonary and carotid arteries and the cardiac output, was estimated to be 30, 19, and 23% of the heat produced during exercise at the three intensities. The kinetics of the increases in muscle and blood temperature were similar, with the greatest change in temperature occurring in muscle (+3.8, 5.2, and 6.1 degrees C after exercise at 40, 65, and 90% of VO2max, respectively). The temperature of blood in the superficial thoracic vein was approximately 2 degrees C below that of arterial blood at rest. This difference had increased to approximately 3 degrees C during the last minute of exercise. The rate of sweating at sites on the back and neck increased with exercise intensity to a common peak of approximately 40 ml.m-2.min-1. If complete evaporation had occurred, water loss in response to exercise (estimated to be 12, 10, and 7.7 liters for the different intensities of exercise) greatly surpassed that required for dissipation of the metabolic heat load.

scholarly journals Counter-current transfer in reproductive biology

Reproduction ◽  
2005 ◽  
Vol 129 (1) ◽  
pp. 9-18 ◽  
Author(s):  
N Einer-Jensen ◽  
RHF Hunter
Keyword(s):  
Venous Blood ◽  
Feedback Regulation ◽  
Systemic Circulation ◽  
Reproductive Organs ◽  
General Distribution ◽  
Current Transfer ◽  
Local Cooling ◽  
Arterial Blood ◽  
Local Feedback ◽  
Counter Current

Heat and substances, including gases, steroids and peptide hormones, can pass from venous blood, interstitial fluid and lymph to the arterial blood; the process is called local counter-current transfer. It has been found in various reproductive organs in many animal species and in man: from the testis to the testis and epididymis; from the ovary to the ovary, tube and tubal corner of the uterus; from the tube and uterus to the ovary; from vagina to uterus; and even between brain blood vessels. Local transfer within the ovary has also been found. Local cooling that creates temperature gradients between organs or within an organ is one aspect of the transfer. Physiologically, the transfer also facilitates local feedback regulation of organ function in a process situated between general distribution of hormones through the systemic circulation and paracrine regulation. Counter-current transfer of drugs after local application opens up new possibilities for treatment.

scholarly journals INVESTIGATIONS ON THE OXYGEN CONTENT OF CUTANEOUS BLOOD (SO CALLED CAPILLARY BLOOD)

1922 ◽  
Vol 36 (5) ◽  
pp. 559-573 ◽  
Author(s):  
Christen Lundsgaard ◽  
Eggert Möller
Keyword(s):  
Oxygen Content ◽  
Venous Pressure ◽  
Venous Blood ◽  
Capillary Blood ◽  
Total Oxygen ◽  
Arterial Blood ◽  
Maximum Value ◽  
Other Substances ◽  
Finger Tip ◽  
Cutaneous Blood

1. A procedure is devised whereby cutaneous blood (so called capillary blood) from a finger-tip can be obtained for gas analyses without coming in contact with the air. 2. Determination was made of the oxygen content of the arterial, cutaneous, and venous blood respectively from a normal resting individual, the arterial and cutaneous blood showing the same oxygen content (97.5 and 96.6 per cent of the total oxygen-combining power of the blood). Venous blood drawn simultaneously was 75 per cent saturated. 3. Using the fact that there is a maximum value for the oxygen-combining power of the blood, we have shown, without doing arterial puncture, that under different conditions (normal and pathological individuals, resting and after exercise) the cutaneous blood and the arterial blood are almost identical as far as the oxygen content is concerned. 4. We think that we are justified in extending the identity, found between the oxygen content of the arterial and cutaneous blood, to other substances in the blood, for instance sugar, salt, uric acid, etc., and also to the reaction of the blood. 5. We are unable to say whether this identity between cutaneous and arterial blood is always true; for example, in a patient with increased venous pressure. 6. In all the experiments we have discarded the first drop of blood, which in some instances was darker than the rest, and always used at least 2 cc. of cutaneous blood. Whether the same results would be obtained with a very small amount of blood, for instance 0.2 to 0.4 cc., we do not know. 7. The experiments show that unless the perfusion of the skin has been extremely great during the experiment, samples of blood obtained from an incision in the skin (of the finger) cannot represent the true capillary blood. The neutral expression cutaneous blood seems therefore for the present preferable to the term capillary blood for samples of blood obtained by cutaneous incisions.

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