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Thermal Physiology and Thermoregulation
Published in James Stewart Campbell, M. Nathaniel Mead, Human Medical Thermography, 2023
James Stewart Campbell, M. Nathaniel Mead
Temperature of the skin's surface largely reflects blood flow through the dermal microvasculature, though larger superficial veins may also warm the skin surface enough to be detected by thermal imagers (Figure 5.3b). Approximately 4% of cardiac output flows through the skin under thermoneutral conditions. This perfusion can increase by more than tenfold via maximal cutaneous vasodilation in response to heat stress, or quickly drop to near zero under severe cold stress.30 Cutaneous blood flow depends mainly on blood circulation in the smallest blood vessels (between 10 and 100 μm in diameter), primarily the arterioles, capillaries, and venules. Whereas the capillary network supplies nutrients and oxygen to the dermal structures, the arterioles are essential for blood flow regulation.31 The regulatory mechanisms include flow-induced vasodilation from wall shear stress, arteriolar myogenic response, and metabolic and autonomic nervous control.32
Optical Methods for Diabetic Foot Ulcer Screening
Published in Andrey V. Dunaev, Valery V. Tuchin, Biomedical Photonics for Diabetes Research, 2023
Robert Bartlett, Gennadi Saiko, Alexandre Yu. Douplik
Diabetes-associated vasculopathy occurs at macrovascular and microvascular levels. The macrovascular disease affects large blood vessels, whereas the microvascular disease affects the very small vessels, less than 300 μm. Some of these vessels contain smooth muscle, which regulates blood flow to the capillary beds. The terminal vessels of the microcirculation are the capillaries that lack smooth muscles.
Nature of Flow of a Liquid
Published in Wilmer W Nichols, Michael F O'Rourke, Elazer R Edelman, Charalambos Vlachopoulos, McDonald's Blood Flow in Arteries, 2022
Hemodynamic factors that tend to affect the magnitude of blood flow disturbances include velocity, viscosity and density of the blood. For example, an increased blood velocity or a reduction of blood viscosity would increase the intensity of turbulence. The pulsatile nature of blood flow may also lead to flow instability. The effects of unsteady flow on the transition from laminar to turbulent flow have been evaluated by several investigators (Hale et al., 1955; Parker, 1977), but an understanding of the stability of unsteady flow, even in tube flow, is still poor (Parker, 1977; Chahed et al., 1991). Lesions that produce a partial obstruction to flow or an irregularity of the vessel wall would augment flow disturbances. The normal aortic and pulmonary valves also cause flow disturbances because the valvular leaflets act as natural projections into the stream of flow (Sabbah and Stein, 1979). Fluttering of the free margin of the leaflets may also contribute to the disturbances.
Modelling and simulation of fluid flow through stenosis and aneurysm blood vessel: a computational hemodynamic analysis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
J. V. Ramana Reddy, Hojin Ha, S. Sundar
Blood vessels play an important role in the circulatory system; These are in the form of tubes that carry blood between the heart and all parts of the body. The blood vessel size varies enormously; in the case of arteries, it varies from 1 mm to 8 µm while 1 mm to 20 µm for veins. An artery carries oxidized blood away from the heart, whereas a vein is the blood vessel that collects and transports blood toward the heart. The general appearance of the arteries is rounded lumen, while veins are irregular and often collapse. As compared to arteries, veins are thin-walled vessels with a large and irregular lumen. The diseases of arteries, veins, and lymph vessels alert to blood flow disorders that affect circulation, thus resulting in disturbance in organ function. An aneurysm is a pathological condition. It weakens the blood vessel wall due to the bulging area in that area, resulting in an abnormal widening or ballooning more significant than 50% of the standard diameter. The arteries are mostly exposed to an aneurysm rather than a vein among the several blood vessels.
Pulsatile flow of thixotropic blood in artery under external body acceleration
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Louiza Cheffar, Abdelhakim Benslimane, Djamel Sadaoui, Adel Benchabane, Karim Bekkour
In most cases, arteries are assumed to be immobile, i.e. under normal physiological conditions. In this case, blood flow is driven by a biological pump: the heart producing a pulsatile pressure gradient in the cardiovascular system (Shit and Roy 2011). However, this excludes other important situations that occur in daily human life, in which the human body is subjected to external body acceleration, e.g. running, driving a vehicle, traveling in an airplane. A long exposure of body to such acceleration in time can leads to many health problems namely: increase in pulse rate, abdominal pain, venous pooling of blood in the extremities (Frolov et al. 2018). To this end, several researchers (Sud et al. 1983; Misra and Sahu 1988; Srivastava et al. 1994; Massoudi and Phuoc 2008) focused their studies on understanding blood flow in arteries under periodic body acceleration.
Intake Duration of Anthocyanin-Rich New Zealand Blackcurrant Extract Affects Cardiovascular Responses during Moderate-Intensity Walking But Not at Rest
Published in Journal of Dietary Supplements, 2023
Mehmet Akif Şahin, Pelin Bilgiç, Stefano Montanari, Mark Elisabeth Theodorus Willems
The present study also provided indication by lower arterio-venous oxygen difference that intake of NZBC extract can enhance tissue oxygen uptake at rest and during dynamic moderate-intensity exercise. Fryer et al. (38, 39) also provided observations of enhanced muscle oxygenation with near-infrared spectroscopy during isometric contractions of forearm skeletal muscles in climbers. It is possible that the presence of lower arterio-venous oxygen difference contributed to performance-enhancing effects in some exercise modalities by intake of NZBC extract (e.g. Ref. (40)). However, the potential benefits of lower arterio-venous oxygen difference, as observed in the present study is unclear. The lower arteriovenous oxygen difference may have been due to enhanced blood flow, compensating for enhanced cardiac output and not indicative of increased oxygen use due to our approach to calculate arteriovenous oxygen difference in the present study. However, the significant increase in cardiac output with 14-days intake of New Zealand blackcurrant without a lower value for arteriovenous oxygen difference may indicate an increase in oxygen uptake.