Organ Microcirculation

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.

The concept of microcirculation means not only the assembly of small vessels-those of less than 100 um in diameter, but also its functional circulatory and metabolic units. Its principal function is to permit the transfer of substances between the tissues and the circulation, making it a fundamental factor in disease processes, including the spread of cancer, delayed healing, circulatory shock, and complications of diabetes . Organ Microcirculation: A Gateway to Diagnostic and Therapeutic Interventions covers the latest developments in nano-biotechnology for microvascular interventions, gastroduodenal microcirculation and disease, liver microvascular research, cell adhesion and traffic in micmcirculation, and the sensing and bioregulation of gaseous molecules in microcirculation . It provides invaluable information for those engaged in microvascular research in the fields of pharmacology, physiology, gastroenterology, and bioengineering.

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 e-book will review special features of the cerebral circulation and how they contribute to the physiology of the brain. It describes structural and functional properties of the cerebral circulation that are unique to the brain, an organ with high metabolic demands and the need for tight water and ion homeostasis. Autoregulation is pronounced in the brain, with myogenic, metabolic and neurogenic mechanisms contributing to maintain relatively constant blood flow during both increases and decreases in pressure. In addition, unlike peripheral organs where the majority of vascular resistance resides in small arteries and arterioles, large extracranial and intracranial arteries contribute significantly to vascular resistance in the brain. The prominent role of large arteries in cerebrovascular resistance helps maintain blood flow and protect downstream vessels during changes in perfusion pressure. The cerebral endothelium is also unique in that its barrier properties are in some way more like epithelium than endothelium in the periphery. The cerebral endothelium, known as the blood-brain barrier, has specialized tight junctions that do not allow ions to pass freely and has very low hydraulic conductivity and transcellular transport. This special configuration modifies Starling's forces in the brain microcirculation such that ions retained in the vascular lumen oppose water movement due to hydrostatic pressure. Tight water regulation is necessary in the brain because it has limited capacity for expansion within the skull. Increased intracranial pressure due to vasogenic edema can cause severe neurologic complications and death.

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

. Besides providing original and stimulating discussion of the topic, the authors aim to encourage the further investigation needed to shed more light on this complex problem, the bane of many transplant recipients. The work will be of interest to all basic and clinical researchers in microcirculation and transplantation.

Microcirculation of blood is the circulation of blood in the smallest of blood vessels, those embedded in the organ tissues. While these are not the first avenues of thought when we consider circulation, they are vital to human health and to the function of the body. Without Microcirculation, our organs would fail, carbon dioxide removal would be reduced and the body would cease to function as it is meant to. This type of blood movement also directly impacts blood pressure and has become a prime focus in modern medical advancements regarding hypertension, also known as high blood pressure. If you, or someone you know or love, suffers from Hypertension, then understanding Microcirculation and upcoming medicines and procedures directly affects you. This book is a scientifically accurate, yet easy to absorb crash course into this fundamental body system. The how's, the whys and the what's are covered in detail, giving the background you need while offering glimpses into the new and exciting world scientists are quickly crafting - a world that targets the Microcirculation of blood in order to control hypertension. Easy to read, easy to understand and easy to enjoy, this book will make you smarter and more prepared for the enticing medical world of tomorrow. Topics: What is Microcirculation? * The Process of Diffusion in the Microcirculation of Blood * Hypertension and its Relation to Microcirculation * Using Microcirculation Knowledge in the Prevention of End-Organ Damage * Bemer Physical Vascular Therapy

The Physiology and Pharmacology of the Microcirculation, Volume 1 discusses the biochemistry, metabolism, pharmacology, and physiology of the general microcirculation. This volume is organized into nine chapters that explore the microcirculation in several organ systems, such as brain, eye, heart, and kidney. The introductory chapters treat the biochemistry of isolated elements of the microvasculature, with special emphasis on the central nervous system. These chapters also explore the microvascular element and the vascular smooth muscle, focusing on their ultrastructural characteristics, innervation, and contraction-relaxation, and the effects of both endogenous and pharmacological vasoactive substances on vascular smooth muscle. The subsequent chapters deal with the exchange mode of the microcirculation; the mechanisms involved in the regulation of transcapillary fluid exchange; and the permeability of capillaries to small and large molecules in a variety of tissues. A discussion on the control mechanisms modulating microcirculatory dynamics is also included. The remaining four chapters are organized to deal with the microcirculation process in selected organs.