Microcirculation

This reference is a volume in the Handbook of Physiology, co-published with The American Physiological Society. Growth in knowledge about the microcirculation has been explosive with the field becoming fragmented into numerous subdisciplines and subspecialties. This volume pulls all of the critical information into one volume. Meticulously edited and reviewed. Benefit: Provides investigators a unique tool to explore the significance of their findings in the context of other aspects of the microcirculation. In this way, the updated edition has a direct role in helping to develop new pathways of research and scholarship Highlights the explosive growth in knowledge about the microcirculation including the biology of nitric oxide synthase (NOS), endothelial cell signaling, angiogenesis, cell adhesion molecules, lymphocyte trafficking, ion channels and receptors, and propagated vasomotor responses. Benefit: Microcirculatory biology has become fragmented into numerous sub-disciplines and subspecialties, and these reference reintegrates the information in one volume

The microcirculation is highly responsive to, and a vital participant in, the inflammatory response. All segments of the microvasculature (arterioles, capillaries, and venules) exhibit characteristic phenotypic changes during inflammation that appear to be directed toward enhancing the delivery of inflammatory cells to the injured/infected tissue, isolating the region from healthy tissue and the systemic circulation, and setting the stage for tissue repair and regeneration. The best characterized responses of the microcirculation to inflammation include impaired vasomotor function, reduced capillary perfusion, adhesion of leukocytes and platelets, activation of the coagulation cascade, and enhanced thrombosis, increased vascular permeability, and an increase in the rate of proliferation of blood and lymphatic vessels. A variety of cells that normally circulate in blood (leukocytes, platelets) or reside within the vessel wall (endothelial cells, pericytes) or in the perivascular space (mast cells, macrophages) are activated in response to inflammation. The activation products and chemical mediators released from these cells act through different well-characterized signaling pathways to induce the phenotypic changes in microvessel function that accompany inflammation. Drugs that target a specific microvascular response to inflammation, such as leukocyte-endothelial cell adhesion or angiogenesis, have shown promise in both the preclinical and clinical studies of inflammatory disease. Future research efforts in this area will likely identify new avenues for therapeutic intervention in inflammation. Table of Contents: Introduction / Historical Perspectives / Anatomical Considerations / Impaired Vasomotor Responses / Capillary Perfusion / Angiogenesis / Leukocyte-Endothelial Cell Adhesion / Platelet-Vessel Wall Interactions / Coagulation and Thrombosis / Endothelial Barrier Dysfunction / Epilogue / References

The Physiology and Pharmacology of the Microcirculation, Volume 2, discusses the microcirculatory function of specific organ systems. The first volume of The Physiology and Pharmacology of the Microcirculation presented some general aspects of microcirculatory function and then concentrated on the microcirculation of a specific organ system, namely, brain, eye, heart, and kidneys. This second and final volume continues the presentation of microcirculatory function of specific organ systems. The book begins with a chapter on the microcirculation of the lungs, with a description of its microcirculatory features and current methods of study. This is followed by separate chapters on the microcirculation of the splanchnic organs. These include the stomach, emphasizing hemodynamics, tissue oxygenation, and control of blood flow; the small and large intestine. Subsequent chapters deal with the microcirculatory responses of both the liver and spleen to different physiological and pharmacological challenges; the microcirculation of the skin, with emphasis on human microcirculation; normal and abnormal microcirculatory dynamics in skeletal muscle; microcirculation of bone; and microcirculation of the salivary glands and exocrine pancreas. The final chapter presents a selective review of pathological events involving the microcirculation, with the emphasis directed toward human diseases.

This book offers an extensive review of the most recent data on the pathophysiological role of structural and functional alterations in the microcirculation, particularly focusing on hypertension and diabetes. It covers several relevant and innovative aspects, including the possible mechanisms involved in the development of microvascular remodeling and rarefaction, the technical approaches available for the detection of microvascular alterations, including non-invasive evaluations, the prognostic role of changes in small resistance artery structure, the possibility of preventing or regressing such alterations with appropriate treatment, and the potential clinical advantages of such intervention. A number of innovative areas of research are considered, including the role of the immune system, inflammation and oxidative stress in the development of microvascular alterations. Lastly, it examines the availability of recent non-invasive methods for the evaluation of small resistance artery morphology in the retina, which in the near future may provide a useful tool for the stratification of cardiovascular risk and even for clinical decisions regarding drug treatment, thus providing physicians with a clinically relevant instrument for improving and optimizing the management of hypertensive and diabetic patients. The book provides valuable, clinically relevant information for specialists (cardiology, internal medicine, and endocrinology) and general practitioners, and also offers novel and stimulating data to basic and clinical researchers.

An Introduction to Microcirculation is written in response to the need for a book containing the most basic information about microcirculation. The book aims to consolidate information gained from the numerous vascular beds that have been used for in vivo microscopic observations, to note the similarities and differences in architecture and function, to reveal the origin of certain terms and concepts, and to discuss hemodynamics of the micro vessels. The book is divided into three parts. Part 1 covers a historical introduction to the study; general anatomical comparisons; the microvasculature of specific organs and tissues; and methods of preparation of tissues for microscopic observation. Part 2 discusses factors that are involved in this process and the exchange in the microcirculation. Part 3 explores the hemodynamics in the microcirculation and quantitative techniques for measurement of velocity and blood pressure. The text is for medical students, graduate students, clinicians, and young investigators who wish to have a greater knowledge on microcirculation and the concepts behind it.

This presentation describes various aspects of the regulation of tissue oxygenation, including the roles of the circulatory system, respiratory system, and blood, the carrier of oxygen within these components of the cardiorespiratory system. The respiratory system takes oxygen from the atmosphere and transports it by diffusion from the air in the alveoli to the blood flowing through the pulmonary capillaries. The cardiovascular system then moves the oxygenated blood from the heart to the microcirculation of the various organs by convection, where oxygen is released from hemoglobin in the red blood cells and moves to the parenchymal cells of each tissue by diffusion. Oxygen that has diffused into cells is then utilized in the mitochondria to produce adenosine triphosphate (ATP), the energy currency of all cells. The mitochondria are able to produce ATP until the oxygen tension or PO2 on the cell surface falls to a critical level of about 4–5 mm Hg. Thus, in order to meet the energetic needs of cells, it is important to maintain a continuous supply of oxygen to the mitochondria at or above the critical PO2 . In order to accomplish this desired outcome, the cardiorespiratory system, including the blood, must be capable of regulation to ensure survival of all tissues under a wide range of circumstances. The purpose of this presentation is to provide basic information about the operation and regulation of the cardiovascular and respiratory systems, as well as the properties of the blood and parenchymal cells, so that a fundamental understanding of the regulation of tissue oxygenation is achieved.

​Since the introduction of coronary angiography, a key technique in understanding coronary artery disease, a number of paradigms regarding its study and interpretation have taken place. Following an emphasis on improved angiographic and subsequent intracoronary imaging techniques, functional assessment of coronary circulation has demonstrated to have major implications for diagnosis and treatment of coronary artery disease. Fractional flow reserve, a pressure derived index of stenosis severity, constitutes the best example of the current importance of physiological assessment in clinical practice. However, the acceptance of FFR by cardiologists contrasts with important voids in knowledge on the basic principles of coronary physiology and of other available techniques that, as an alternative to FFR, allow a more comprehensive assessment of coronary circulation. This is particularly noticeable in the assessment of microcirculation, an unavoidable compartment of coronary circulation that is frequently affected in acute coronary syndromes of in the presence of cardiovascular risk factors or non-coronary heart disease. A deeper understanding of the relationship between epicardial vessel and microcirculatory involvement has started with the advent of newer imaging techniques like invasive optical coherence tomography, and non-invasive CT and NMR techniques. This book aims to be an indispensable tool for clinicians and researches in the field of coronary artery disease. It provides a balanced, comprehensive review of anatomy, physiology and available techniques, discusses both the diagnosis of epicardial vessel and microcirculatory disease, the impact of different diseases at different levels of coronary circulation, and the best way to address a separate or combined assessment of different levels of coronary circulation. ​