Blood vessels veins

Special small ultrasound transducers, often referred to as endoscopic transducers, have been designed which can be inserted into blood vessels to examine blockages in arteries (43). These transducers operate at approximately 20 MHz and have a viewing distance of less than a centimeter. Such devices are capable of producing ultrasound images of the inside of arteries and veins. The quaUty of the ultrasound image is sufficient to determine the type of blockage. 

G.E., abbrev. (Gewichtseinheit) unit of weight. Geilder, n. veins, veined structure system of blood vessels. 

Vessel identity represents one of the major differentiation processes during blood vessel formation. Arteries and veins are structurally and functionally... 

Thrombophlebitis Inflammation of a blood vessel (e.g., vein) associated with the stimulation of clotting and formation of a thrombus (or blood clot). 

The adenohypophysis does not have a direct anatomical connection with the hypothalamus therefore, regulation of hormone secretion by way of neuronal signals is not possible. Instead, these two structures are associated by a specialized circulatory system and the secretion of hormones from the adenohypophysis is regulated by hormonal signals from the hypothalamus (see Figure 10.2). Systemic arterial blood is directed first to the hypothalamus. The exchange of materials between the blood and the interstitial fluid of the hypothalamus takes place at the primary capillary plexus. The blood then flows to the adenohypophysis through the hypothalamic-hypophyseal portal veins. Portal veins are blood vessels that connect two capillary beds. The second capillary bed in this system is the secondary capillary plexus located in the adenohypophysis. 

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. 

In other words, it is a measure of the inherent distensibility of the blood vessels. The more compliant the vessel is, then the greater the volume of blood that it is capable of accommodating. As mentioned, all blood vessels are compliant. However, the marked difference in distensibility between arteries and veins is illustrated by the following ... 

The effect of sympathetic stimulation on venous resistance is minimal. As previously stated, it is the larger, less flexible veins that provide resistance to blood flow. However, these blood vessels are sparsely innervated therefore, little change takes place in vessel radius and physiological effect on blood flow is relatively insignificant. 

The liver is a large and distensible organ. As such, large quantities of blood may be stored in its blood vessels providing a blood reservoir function. Under normal physiological conditions, the hepatic veins and hepatic sinuses contain approximately 450 ml of blood, or almost 10% of blood volume. When needed, this blood may be mobilized to increase venous return and cardiac output. 

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...

Blood is supplied to the kidneys via the renal vein, a branch of the descending vena cava, at relatively high pressure to ensure rapid filtration of plasma across the membranes of the blood vessels in the glomeruli and the epithelial cells of the Bowman s capsule. The net filtration pressure of about 5-6 kPa, is the difference between the blood pressure forcing plasma water across the filtration barrier and the opposing osmotic and... 

This technique, also referred to as the auto-perfused method after experiments by Windmuller and Spaeth [67] involves cannulation and drainage of a vein from an intestinal segment and donor blood replacement via a sustainable blood vessel (e.g. jugular vein). The most commonly reported site of cannulation is the mesenteric vein. Cannulation is performed as follows. A midline incision of 4 cm is made and an 8-12-cm segment of the ileum is located to... 

The most prescribed drugs for blood-related disorders are also summarized in Table 1.17. Blood clots can occur in the veins at extremities (especially after a long period of immobility). Those clots can subsequently become lodged in the blood vessels, the atria, the heart valves, and within the lungs, causing embolism and shortness of breath. Under severe conditions, the clots can also obstruct the flow of blood to the brain, leading to a stroke and paralysis. Coumadin (warfarin see chemical structure below) is one of the main hematological compounds that has been widely prescribed to counter these conditions... 

Thus the effect of ELBI on the aorta and vein endothehocytes depends on the duration of irradiation. Irradiation for 15 and 30 min caused reversible changes which were expressed in changes of the normal cell forms, appearance of craterlike depressions and surface defects, swelling of nuclei and oedema. Irradiation for 60 min had a more pronounced effect on the inner surface of blood vessels resulting in detachment of endothehocytes from the basal membrane and their desquamation. Restoration of the endothelial structure after 15 and 30 min of laser irradiation... 

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