Blood vessels arterioles

Resistance vessels Microcirculatory blood vessels (arterioles, pre-capillary... 

The kidneys play an important role in maintaining a proper environment for the cells in the body. By regulating the excretion of water, salts and metabolic end products, the kidneys control the plasma osmolality (i.e., the concentration of ions in the blood), the extracellular fluid volume, and the proportions of various blood solutes. The kidneys are also involved in the production of a set of hormones that make the blood vessels (arterioles) contract in the kidneys as well as in other parts of the body. These hormones can give rise to changes in the vascular structure, and... 

Blood vessels Arterioles Dilatation (muscarinic) Skin, intestine Contraction (a,)... 

In order to understand the ways heparin inhibits the response of the organism to injurious agents and limits the extent of the inflammatory response, it is necessary first to be familiar with the constituents of loose connective tissue. This tissue acts as a packing material for the blood vessels and cells. The small blood vessels, arterioles, and capillaries are imbedded in an amorphous gelantinous material. There is actually no place in the organism where a blood vessel comes in immediate contact with the parenchymal cell. 

The microcirculation is comprised of blood vessels (arterioles, capillaries, and venules) with diameters of less than approximately 150 /xm. The importance of the microcirculation is underscored by the fact that most of the hydrodynamic resistance of the circulatory system Hes in the microvessels (especially in arterioles) and most of the exchange of nutrients and waste products occurs at the level of the smallest microvessels. The subjects of microcirculatory research are blood flow and molecular transport in microvessels, mechanical interactions and molecular exchange between these vessels and the surrounding tissue, and regulation of blood flow and pressure and molecular transport. Quantitative knowledge of microcirculatory mechanics and mass transport has been accumulated primarily in the past 30 years owing to significant innovations in methods and techniques to measure microcirculatory parameters and methods to analyze microcirculatory data. The development of these methods has required joint efforts... 

The nitrates, such as isosorbide (Isordil) and nitroglycerin, have a direct relaxing effect on die smooth muscle layer of blood vessels. The result of diis effect is an increase in the lumen of die artery or arteriole and an increase in the amount of blood flowing through diese vessels. An increased blood flow results in an increase in die oxygen supply to surrounding tissues. 

Telangiectasia Permanent dilation of preexisting small blood vessels (capillaries, arterioles, and venules), usually in the skin or mucous membranes, which presents as a coarse or fine red mark. 

The circulatory system is composed of several anatomically and functionally distinct blood vessels including (1) arteries, (2) arterioles, (3) capillaries, and (4) veins. 

The sympathetic system also innervates vascular smooth muscle and regulates the radius of the blood vessels. All types of blood vessels except capillaries are innervated however, the most densely innervated vessels include arterioles and veins. An increase in sympathetic stimulation of vascular smooth muscle causes vasoconstriction and a decrease in stimulation causes vasodilation. Constriction of arterioles causes an increase in TPR and therefore MAP. Constriction of veins causes an increase in venous return (VR) which increases end-diastolic volume (EDV), SV (Frank-Starling law of the heart), CO, and MAP. 

Blood vessel A tube in the body through which blood circulates. Blood vessels include a network of arteries, arterioles, capillaries, venules, and veins. [NIH]... 

Figure 5.2 Cross section through bLood vessels (a) an artery. Sizes of arteries vary from 25 mm diameter with 2 mm wall thickness in the aorta to 20 pm diameter with a 15 pm wall thickness in the smallest arterioles, (b) a vein. Note there are no elastic lamellae in veins so tension is maintained by elastic fibres which are arranged within the media. Typically, veins are approximately 5 mm in diameter but with a very thin wall, for example 0.5 mm. The vena cava is the largest vein at 30 mm diameter...

In medical practice, a-adrenoblockers are drngs that block a - and o -adrenoreceptors, and they are nsed relatively rarely. The most important effect of a-adrenoblockers is the dilation of blood vessels, for which they are nsed in various disturbances of peripheral blood flow, and hemorrhagic and cardiogenic shock, in which the typical effect is a spasm of the arterioles. 

Norepinephrine, administered to a normotensive adult either subcutaneously or by slow intravenous injection, constricts most blood vessels. Venules as well as arterioles are constricted. As a consequence, there is a net increase in the total peripheral resistance. 

A slow intravenous injection of histamine produces marked vasodilation of the arterioles, capillaries, and venules. This causes a fall in blood pressure whose magnitude depends on the concentration of histamine injected, the degree of baroreceptor reflex compensation, and the extent of histamine-induced release of adrenal catecholamines. Vasodilation of cutaneous blood vessels reddens the skin of the face, while a throbbing headache can result from vasodilation of brain arterioles. Vasodilation is mediated through both Hj- and Hj-receptors on vascular smooth muscle. Stimulation of Hj-receptors produces a rapid and short-lived response, whereas stimulation of H2-receptors produces a more sustained response that is slower in onset. Stimulation of Hj-receptors on sympathetic nerve terminals inhibits the release of norepinephrine and its associated vasoconstriction. 

Physiologically, in both normal and hypertensive individuals, blood pressure is maintained by moment-to-moment regulation of cardiac output and peripheral vascular resistance, exerted at three anatomic sites (Figure 11-1) arterioles, postcapillary venules (capacitance vessels), and heart. A fourth anatomic control site, the kidney, contributes to maintenance of blood pressure by regulating the volume of intravascular fluid. Baroreflexes, mediated by autonomic nerves, act in combination with humoral mechanisms, including the renin-angiotensin-aldosterone system, to coordinate function at these four control sites and to maintain normal blood pressure. Finally, local release of vasoactive substances from vascular endothelium may also be involved in the regulation of vascular resistance. For example, endothelin-1 (see Chapter 17) constricts and nitric oxide (see Chapter 19) dilates blood vessels. 

In Figure 15.1 only the large arteries and veins are shown. However, in the organs and tissues, the arteries branch into many smaller blood vessels - the arterioles - which further branch into many fine blood vessels that range from 5 to 20 pm in inner diameter, and are termed capillaries. Various nutrients and... 

To implement the hemodynamic coupling in our model, a piece of common afferent arteriole is included into the system, and the total length of the incoming blood vessel is hereafter divided into a fraction s < that is common to the two interacting nephrons, a fraction 1 — that is affected by the TGF signal, and a remaining fraction — e for which the flow resistance is considered to remain constant As compared with the equilibrium resistance of the separate arterioles, the piece of shared arteriole is assumed to have half the flow resistance per unit length. 

Blood vessels include capillaries, arterioles, arteries, and veins. Each of these structures is composed of three layers the intima, media, and adventitia (Figure 3.12). For example, in elastic arteries the wall consists of an intimal layer containing endothelial cells and connective tissue a media containing smooth muscle cells, collagen, and elastic fibers and an adventitia containing collagen fibers, nerves, and blood vessels. In cross-section,... 

The mechanical force most relevant to platelet-mediated thrombosis is shear stress. The normal time-averaged levels of venous and arterial shear stresses range between 1-5 dyn/cm2 and 6 10 dyn/cm2, respectively. However, fluid shear stress may reach levels well over 200 dyn/cm2 in small arteries and arterioles partially obstructed by atherosclerosis or vascular spasm. The cone-and-plate viscometer and parallel-plate flow chamber are two of the most common devices used to simulate fluid mechanical shearing stress conditions in blood vessels. 

Capillaries The tiniest blood vessels capillary networks connect the arterioles (the smallest arteries) and the venules (the smallest veins)... 

Figure 2.16. Nephron function, a Filtration occurs in the glomerulus. The filtrate is fuimeled into the tubule, b Schemat-ie of the blood vessel wall stiueture in the glomeralus. Both the endothelium within and the podocytes outside the arterioles have sUts and fenestrations that are a few nanometers wide. As in the eapillaries elsewhere in the body, the basal membrane functions as the sieve, e In the tubule and the colleeting duct, the filtrate is extensively post-proeessed water, substrates and ions are reabsorbed but also aetively secreted and exchanged. Tubular processing is under hormonal control.

Previous studies have shown that accommodation mediated via ciliary smooth muscle activity also receives sympathetic innervation. Sympathetic nerves reach the ciliary muscle through the uveal blood vessels in close association with arteries and terminal arterioles. The distribution of the adrenergic fibers in the ciliary muscle appears to vary across species. In primates sympathetic nerve terminals, mainly 3 receptors, can generally be found in the anterior portion of the ciliary muscle. The accommodative amplitude significantly decreased in human subjects after instillation of phenylephrine (an a agonist) or hydroxyamphetamine (an a and (3 agonist). Such observations provide evidence that both sympathetic and parasympathetic divisions of the autonomic nervous system can affect accommodation but not equally. Furthermore, the nature of sympathetic innervation can be summarized as follows ... 

Now, what could eye exams possibly have to do with blood pressure, you might reasonably ask Well, it turns out that the eyes may be the window through which to look for potential future hypertension. The little arterioles that supply blood to the retina apparently get narrower before blood pressure elevations proceed to hypertension an eye doctor can spot the narrowing before blood pressure goes up at all. An investigation in Sydney, Australia, called the Blue Mountain Eye Study found that people with narrowed blood vessels in the eyes were twice as likely as people with... 

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