Vascular system vasculatur

Blood is a unique tissue in that it is (obviously) a fluid. A typical 70 kg adult male has about 51 of whole blood coursing his vasculature at any time. The dynamics of the blood-vascular system are impressive many millions of cells are released from the bone marrow each day a red cell will travel over 250 miles (400 km) during its relatively short life span (120 days), and an endothelial cell lining the lumen of a blood vessel will... 

Osteocytes also rapidly release nitric oxide in response to stress [160, 105] and this NO response seems to be required for the stress-related prostaglandin release [105]. Therefore, the behavior of osteocytes compares to that of endothelial cells which regulate the flow of blood through the vascular system, and also respond to fluid flow of 0.5 Pa with increased prostaglandin and nitric oxide production [79]. The response of endothelial cells to shear stress is likely related to their role in mediating an adaptive remodeling of the vasculature, so as to maintain constant endothelial fluid shear stress throughout the arterial site of the circulation [99],... 

Blood normally is maintained in the fluid state so that nutrients can be delivered to the various tissues of the body. When the integrity of the vascular system has been compromised, it becomes necessary for the blood to clot. As shown in Figure I, the initial response to a break in the continuity of the vasculature is the formation of the platelet plug. Platelets in the flowing blood rapidly adhere to the exposed... 

In addition to studying hemodynamic changes caused by liberated histamine, plasma epinephrine and norepinephrine levels have been investigated following injection of morphine. In a study of a patient who experienced an anaphylactoid response following the intravenous injection of morphine 0.3 mg/kg, plasma catecholamines were increased and this was accompanied by decreases in systemic vascular resistance and arterial blood pressure. In another study, intravenous morphine increased cardiac output, histamine, and epinephrine plasma concentrations and decreased arterial blood pressure and systemic vasculature resistance in adult subjects with no history of drug allergy or clinical evidence of cardiovascular, pulmonary, or metabolic disease. 

In this section, some of the characteristics of blood flow are described with emphasis on the fact that blood is a suspension of particulates. First, the types of cells present in human blood are described, and the flow of blood through the human vasculature is discussed with emphasis on the multiscale nature of the relevant phenomena. As an example of bioengineering research dealing with the vascular system, some of the transport-related aspects of the onset of atherosclerois are discussed. Finally, the use of DNS to model suspensions of red blood cells is reviewed, and prospects for multiscale models of transport phenomena associated with blood are discussed. 

The resting membrane potential of most excitable cells is around —60 to —80 mV. This gradient is maintained by the activity of various ion channels. When the potassium channels of the cell open, potassium efflux occurs and hyperpolari2ation results. This decreases calcium channel openings, which ia turn preveats the influx of calcium iato the cell lea ding to a decrease ia iatraceUular calcium ia the smooth muscles of the vasculature. The vascular smooth muscles thea relax and the systemic blood pressure faUs. 

Diseases affecting skeletal muscle are not always primary diseases of muscle, and it is necessary first to determine whether a particular disorder is a primary disease of muscle, is neurogenic in origin, is an inflammatory disorder, or results from vascular insufficiency. A primary disease of muscle is one in which the skeletal muscle fibers are the primary target of the disease. Neurogenic disorders are those in which weakness, atrophy, or abnormal activity arises as a result of pathological processes in the peripheral or central nervous system. Inflammatory disorders may result in T-cell mediated muscle damage and are often associated with viral infections. Vascular insufficiency as a result of occlusion in any part of the muscle vasculature can cause severe disorders of muscle, especially in terms of pain, metabolic insufficiency, and weakness. 

Direct vasoconstriction is mediated by the stimulation of vascular 5-HTib receptors. These receptors are also found systemically, so coronary arteries also undergo vasoconstriction. Sumatriptan constricts cerebral arteries, but if the vasculature is normal, this does not affect rCBF. 

NO is a gaseous neurotransmitter implicated in signaling in the central and peripheral nervous system as well as in the immune system and the vasculature. NO is formed from L-arginine by nitric oxide synthase (NOS). There are three isoforms of NOS. All isoforms require NADPH as a cofactor, use L-arginine as a substrate, and are inhibited by Nw-nitro-L-arginine methyl ester (L-NAME). The three isoforms are separate gene products. One isoform of NOS is a cytosolic, calcium/calmodulin-independent, inducible enzyme (iNOS). It is found in macrophages, neutrophils, vascular smooth muscle, and endothelia. The iNOS... 

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