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October, 2006
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Blood Vessels: Any of the tubular vessels conveying the blood (arteries, arterioles, capillaries, venules, and veins).

Blood Flow

JoVE 10888

Blood is pumped by the heart into the aorta, the largest artery in the body, and then into increasingly smaller arteries, arterioles, and capillaries. The velocity of blood flow decreases with increased cross-sectional blood vessel area. As blood returns to the heart through venules and veins, its velocity increases. The movement of blood is encouraged by smooth muscle in the vessel walls, the movement of skeletal muscle surrounding the vessels, and one-way valves that prevent backflow. Somewhat counterintuitively, the velocity of blood flow decreases as it enters blood vessels with smaller diameters. If a hose is squeezed, decreasing its diameter, water will squirt out faster and harder, but this does not occur when blood moves into blood vessels with smaller diameters. This is because blood does not simply move from one blood vessel into a smaller one, but travels from a blood vessel into multiple smaller blood vessels. The total cross-sectional area of these smaller blood vessels is greater than that of the original blood vessel. Additionally, the decreased diameter of individual vessels creates increased resistance. Therefore, as blood enters smaller blood vessels, it slows down, providing time for gas exchange to occur through the walls of small capillaries. Blood flow is directed by vasodilation and vasoconstriction. Chemical signals can cause blood

 Core: Biology

Physiology of the Circulatory System- Concept

JoVE 10625


Conditions in the external environment of an organism can change rapidly and drastically. To survive, organisms must maintain a fairly constant internal environment, which involves continuous regulation of temperature, pH, and other factors. This balanced state is known as homeostasis, which describes the processes by which organisms maintain their optimal internal…

 Lab Bio

Vasodilation of Isolated Vessels and the Isolation of the Extracellular Matrix of Tight-skin Mice

1Department of Anesthesiology, Medical College of Wisconsin, 2Clement J. Zablocki Veterans Affairs Medical Center, 3Department of Surgery, Division of Pediatric Surgery, Children's Research Institute, 4Department of Orthopedic Surgery, Medical College of Wisconsin, 5Deptarment of Anesthesiology, Clement J Zblocki Veteran Affairs Medical Center, 6Department of Medicine, Division of Cardiology, Medical College of Wisconsin

JoVE 55036

 Immunology and Infection

Computational Fluid Dynamics Simulations of Blood Flow in a Cerebral Aneurysm

JoVE 10479

Source: Joseph C. Muskat, Vitaliy L. Rayz, and Craig J. Goergen, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, Indiana

The objective of this video is to describe recent advancements of computational fluid dynamic (CFD) simulations based on patient- or animal-specific vasculature. Here,…

 Biomedical Engineering

The Blood-brain Barrier

JoVE 10841

The blood-brain barrier (BBB) refers to the specialized vasculature that provides the brain with nutrients in the blood while strictly regulating the movement of ions, molecules, pathogens, and other substances. It is composed of tightly linked endothelial cells on one side and astrocyte projections on the other. Together they provide a semipermeable barrier that protects the brain and poses unique challenges to the delivery of therapeutics. The BBB is made up of a variety of cellular components, including endothelial cells and astrocytes. These cells share a common basement membrane and together regulate the passage of components between the circulation and the interstitial fluid surrounding the brain. The first type of cellular component, specialized endothelial cells, make up the walls of the cerebral capillaries. They are connected by extremely tight and complex intercellular junctions. These junctions create a selective physical barrier, preventing simple diffusion of most substances, including average to large-sized molecules such as glucose and insulin. A second cell type, astrocytes, are a type of glial cell of the central nervous system which influences endothelial cell function, blood flow, and ion balance in the brain through interaction and close association with cerebral vasculature. They provide a direct link between the vasculature

 Core: Biology

Blood Withdrawal I

JoVE 10246

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN

Blood collection is a common requirement for research studies that involve mice and rats. The method of blood withdrawal in mice and rats is dependent upon the volume of blood needed, the frequency of the sampling, the health status of the …

 Lab Animal Research

Blood Withdrawal II

JoVE 10247

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN

The collection of blood from mice and rats for analysis can be done through a variety of methods. Each method of collection has variations in the type of restraint required, the invasiveness of the procedure, and the necessity of a general …

 Lab Animal Research

Anatomy of the Circulatory System

JoVE 10885

The human circulatory system consists of blood, blood vessels that carry blood away from the heart, around the body, and back to the heart, and the heart itself, which acts as a central pump. The systemic circuit supplies blood to the whole body, the coronary circuit supplies blood to the heart, and the pulmonary circuit supplies blood flow between the heart and lungs.

Blood travels from the right atrium to the right ventricle of the heart through the tricuspid valve, then from the right ventricle to the pulmonary artery through the pulmonary valve. Pulmonary veins then carry the blood to the left atrium of the heart, from which it is carried to the left ventricle through the mitral valve. Finally, the left ventricle pumps blood to the aorta (the largest artery in the body) through the aortic valve. Arteries, which carry blood away from the heart, split and get progressively smaller, becoming arterioles and eventually a series of capillaries, the sites of gas exchange. Capillaries converge to become larger venules, and eventually merge into veins, which bring blood back to the heart. Humans have a double circulatory system, in which blood travels through the heart twice via the pulmonary and systemic circuits. First, the heart receives deoxygenated blood in its right side and then pumps it to the nearby pulmonary circuit, the capillaries that ar

 Core: Biology


JoVE 10902

In response to tissue injury and infection, mast cells initiate inflammation. Mast cells release chemicals that increase the permeability of adjacent blood capillaries and attract additional immune cells to the wound or site of infection. Neutrophils are phagocytic leukocytes that exit the bloodstream and engulf invading microbes. Blood clotting platelets seal the wound and fibers create a scaffold for wound healing. Macrophages engulf aging neutrophils to end the acute inflammatory response. Tissue injury and infection are the primary causes of acute inflammation. Inflammation protects the body by eliminating the cause of tissue injury and initiating the removal of cell debris resulting from the initial damage and related immune cell activity. Inflammation involves mediators of both the innate and adaptive immune system. Proper regulation of inflammation is crucial to clear the pathogen and remove cell debris without overly damaging healthy tissue in the process. If inflammatory processes are not properly regulated, chronic inflammation can arise that is often fatal. Mast cells are the first to respond to tissue injury, as they are primarily located in areas that have contact with the exterior: the skin, gut, and airways. Mast cells have an arsenal of receptors on their cell surface and can hence be activated by a wide variety of stimuli, such as mi

 Core: Biology

Hormonal Regulation

JoVE 10893

The renin-aldosterone system is an endocrine system which guides the renal absorption of water and electrolytes, thus managing blood pressure and osmoregulation. Activation of the system begins in the kidneys with a small cluster of cells adjacent to the afferent and efferent blood vessels of the renal corpuscle. As the nephrons are filtering blood, juxtaglomerular cells monitor blood pressure. If they detect a decrease in pressure, they release the hormone renin into the bloodstream. Circulating renin interacts with angiotensinogen, a precursor protein synthesized by the liver, to create angiotensin I. A final step cleaves angiotensin I into angiotensin II, a process achieved by angiotensin-converting enzyme, or ACE, which is released by the lungs. Angiotensin II temporarily increases blood pressure by contracting smaller blood vessels. It also induces the release of aldosterone from the adrenal cortex of the kidneys. Aldosterone directly stimulates the reabsorption of sodium and the excretion of potassium by the kidneys to maintain electrolyte balance. Moreover, circulating levels of aldosterone stimulate the release of antidiuretic hormone, or ADH, by the hypothalamus in the brain. Upon reaching the kidneys, ADH upregulates aquaporin channels in the nephrons which increase the water retention in the blood vessels. The combined effects of

 Core: Biology
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